ISSUE: Electric Brake Controller connection to 2002 Ford F550 Chassis

[Miles F]

ISSUE: Class A, 2002 Itasca Sunrise 34D motorhome on a 2002 Ford F550 Chassis WITH a tow package BUT configured for trailer lights ONLY, NOT with electric brakes; and how to connect the red “STOPLIGHT” cable on the electric brake controller harness (in this case a Tekonsha Primus IQ controller).

NOTE: I am an electrician with knowledge on 12v systems so your answer can be technical.

The motorhome manual does not mention a tow package and I cannot find any under-dash plug for this). HOWEVER, as mentioned there is a factory fitted trailer hitch 6 pin connector BUT only configured for trailer lighting. So I got an electric brake controller that comes with a harness with bare wires that allows me to wire in everything myself. I need to know what to splice the controller harness RED “STOPLIGHT” cable to with THIS following issue:

The Tekonsha Primus IQ brake controller box contained a warning leaflet which warns of older Fords where the brake pedal switch has a red with green stripe cable which is 12V HOT when the brake pedal is depressed AND when pedal is NOT depressed it goes directly to GROUND. It states that the red “STOPLIGHT” cable on the Tekonsha Primus IQ harness must NOT be connected to that red with green stripe cable as it will blow the controller when “Manual” control is selected on the controller when setting the power level or when driving. There IS NOT a red with green stripe cable BUT I discovered the same issue with other cables, as follows:

SO, it states to INSTEAD splice to the light green cable on the brake pedal switch. NOW, it DOES have a light green cable BUT this cable IS the one that is 12V HOT when the brake pedal is depressed, and WHEN pedal is not depressed it goes directly to GROUND. So surely I cannot use that light green cable as suggested either for the same reason.

There are 4 cables in total on the brake pedal switch as follows:

1. The above mentioned light green cable: brake pedal depressed = 12V HOT; brake pedal NOT depressed = directly to GROUND
2. Light green with red stripe: 12V HOT all the time (obviously the 12v +ve cable to the switch).
3. Blue with black stripe: 12V HOT all the time (possibly to do with cruise control?)
4. Black with blue stripe: GROUND all the time

***So what do I splice/connect the electric brake controller harness RED “STOPLIGHT” cable to so it receives the correct signals (i.e. when brake pedal depressed = 12V HOT; brake pedal NOT depressed = OPEN CIRCUIT)? (And it must not affect other vehicle systems, e.g. cruise control, transmission etc.)

I pray this all makes sense and that someone has the miracle answer. Thank you for all your help.

[chboone]

Ford Class A motorhome chassis is an F53 and do not come from factory with tow package installed. It is up to the motorhome manufacturer to install the hitch and trailer connector. Ford installed the blue wire that runs from the under dash connector to end of the frame. Seldom do the motorhome manufacturer's finish running the blue wire to the 7 pin trailer connector. The F53 is ship with the brake trailer controller connector tye wrapped to left side of the steering column, mine had a plastic bag on it. It is hard to find the under dash connector because it is high up.
The F550 is a delivery truck chassis.

[l1v3fr33ord1]

MilesF-

Welcome to iRV2!

As "chboone" wrote, your coach came with a connector under the dash and a disconnected blue trailer electric brake wire at the rear. The wiring diagram for your coach (Auto Lamps Wiring Diagram, Sheet 3, Zone B-1, link here) confirms this.

To use what Ford and Winnebago provided you need to find and extend the blue wire to the trailer hitch connector, and buy a Tekonsha adapter to connect the trailer electric brake controller to the Ford connector under the dash. The most common adapter to use on the F-53 is the 3035-P, link here. This adapter makes the controller install at the dash plug-and-play. Please confirm for yourself that this is the correct adapter for your controller and your chassis' Ford trailer electric brake controller under-dash connector.

The diagram below shows how the Ford trailer electric brake controller connector is wired.

Here is a link to all of the wiring diagrams for your coach. Additional information is available via Winnebago Owner Resources, link here.

Finally, you should add a "signature" to your profile. It contains whatever info you want; most people put info about their coach there, so they don't have to type it into each message. Instructions for adding a signature are here.

[Miles F]

THANK YOU chboone and l1v3fr33ord1 so much for responding so quickly and spending the time to find certain files and references for me. Here is some more information.

Firstly, I am wondering if "F53" is another coding for what is displayed on the FORD Description and Spec Sheet that was in the Info Pack folder bag in the vehicle when I purchased the vehicle (used). It states at the top that is is a FORD F550 Strip Chassis.
Now, I see in the VIN, it starts 1FCNF53S32 where I have bolded the "F53" part in there. Is F53 just another code for the same type, i.e. F550 chassis for motorhome purposes? See below image:



OK, on to the wiring diagrams. Thank you very much for providing the wiring diagrams and page reference. I already had the 2003 wiring diagrams (which are the same essentially) because I thought I would get the year the coach was completed and registered in early 2003, even though it is on a 2002 Ford chassis.
Going by the wiring diagram you gave me the link for (2002), I see the Hitch 6 pin connector wiring (see image below) which matches what I have (where pin S is empty - which I would use for the blue Brake Controller Output cable) and the remaining pins are for ground and all the rear lights.



OK, so here is what I have discovered so far:

1. There is no connector under the dash (not anywhere around the steering column from top to bottom, and I looked extensively under all the dash around the driver station also, taking dash and steering column panels off to reveal just about everything). I assumed it would be a receptacle connector, disconnected that would be there ready to fit the 3035-P adaptor you mentioned. I see nothing like that.

2. Ref: "disconnected blue trailer electric brake wire at the rear" - There is also no obvious blue cable at the end of the frame. I have not looked further back than 1 foot inside the cable loom/harness (black split wire loom tubing) that goes to the rear lights, which is separate to the hitch cable loom/harness. However, I would not expect to find it there. Is is also not in the current hitch connector loom/harness that correlates to the wiring diagram (certainly not in the last foot of loom/harness. Also the wiring diagram shows a number of cables as "NOT USED" (see above image of cables in chassis harness), one of which is the blue cable (I do not know whether or not "NOT USED" means it was never fitted or, as you said, it was fitted but is open ended/disconnected and tied somewhere near the rear end).

3. I am unaware of there is any other cable under the dash that I can splice to that provides: brake pedal depressed = 12V HOT; brake pedal NOT depressed = OPEN CIRCUIT (as the Tekonsha Primus IQ electric controller instructions require). The brake switch has the following colors and meter readings:

• Light green cable: brake pedal depressed = 12V HOT; brake pedal NOT depressed = directly to GROUND
• Light green with red stripe: 12V HOT all the time (obviously the 12v +ve cable to the switch).
• Blue with black stripe: 12V HOT all the time (possibly to do with cruise control?)
• Black with blue stripe: GROUND all the time

I cannot use the light green cable the Primus IQ instructions suggest as an alternative for Ford Trucks because it warns of not using any cable that provides: brake pedal NOT depressed = directly to GROUND
(and by the way, the hitch connector pins LT and RT wiring (see above image again) that are for the stop/brake lights as well as turn signal lights, ALSO provide the same: brake pedal depressed = 12V HOT; brake pedal NOT depressed = directly to GROUND).

The brake pedal brake switch cables are thin (possibly 16 or 18 gauge) and go straight off into a loom under the dash, and so I presume the Light Green cable goes to a relay, the output of which are the yellow and white cables (colors used by Winnebego for much of the other coach wiring) that go all the way to the rear hitch 6 pin connector. Though, it baffles me why these cables that go to the hitch 6 pin connector for the stop/brake lights go directly to GROUND when the brake pedal NOT depressed.

Before posting the original issue, and because I had not found any of what I expected under the dash, I already had wired/loomed a new blue 10 gauge cable from the rear hitch 6 pin connector all the way to the dash board area to crimp to the Primus IQ wiring harness (which comes as four bare wires for the vehicle side - blue, red, white, black), and I also have already wired/loomed a cable (12V Direct from Battery with 20A Auto-Reset circuit breaker, and from battery -ve (Ground) - ready to crimp to this Primus IQ harness. I just assumed there would be an easy brake signal cable to connect to with the correct readings.

So, it all comes down to finding a suitable stop light signal cable (to splice to the red cable on the Primus IQ controller wiring harness). So I pray again this all makes sense and that you will know what the work around solution.

ALL HELP IS SO GRATEFULLY RECEIVED.

[l1v3fr33ord1]

Miles F-

Ford's VIN decoder is here. The results says you have an F-53 (the 5th, 6th and 7th positions).

Attached find a diagram set that should help you figure things out.

The first sheet shows the brake switch should present an open circuit when the brake pedal is not depressed.

The connectors shown on sheet 15 are the same two that are on the Winnebago drawing. The wire colors and functions match.

[Miles F]

Thank you, Mark, thnak you again for finding wiring diagrams.

Yes, I can see from the first page of the diagrams (SHEET 3) that the brake switch should be open circuit at pin 4 of C278 when the pedal is not depressed, as you said.

However, I checked again with multimeter (brake pedal not pressed, first with ignition on and then off) at the light green cable at that pedal brake switch (which the diagram shows to be that pin 4 of C278) to a Ground stud (on the wall behind the pedals) on continuity beeper setting and got the beep, and then with ohmeter and it showed 1.2 ohms, so it is definitely going to Ground. This is either a faulty brake switch or *Ford changed something.

*I say that because I mentioned in my thread about a warning leaflet in the Tekonsha Primus IQ brake controller box (see image below of this warning):



So Tekonsha obviously knew of this Ground being present at that switch, up to a certain year in the F53 anyway (even if it is no longer the case). Because, although they state a different wire color in the warning, the issue of the switch at pin 4 of C278 when the pedal is not depressed going to Ground is still present in this wiring set up.

Any ideas where the harness shown on sheet 19 is under the dash? And what does "ENDS IN HARNESS" mean? It would seem not to "suggest" it is a connector. As I have said, I looked everywhere near the steering column and elsewhere and saw nothing relating to those colors (blue, green red, white). Even if I did though, going by the diagram (S218 on SHEET 3) where the green cable runs through to the green cable on SHEET 19, I would still see the same meter readings (as is also present at the trailer connector pins).

If you do have any ideas it would be so helpful. I appreciate all you are doing to help. All my research so far, with yours too does not seem to be the case on this rig.

Blessings beyond to you, Mark. Hope to hear from you soon.

[grtharris]

Miles F, has mention above your coach has a connector supplied by Ford to connect your brake control to. Attached are two documents one is the SVE Bulletin showing to location of the connector. Before 2011 is was located behind the instrument cluster and hard to get to. The second document is the Ford wiring diagram showing the actual brake switch, you will see there are two circuits, one for the chassis systems and the other for the brake controller.
Just added another Ford drawing showing the location of the C210 connector and pin out.

[Miles F]

THANK YOU very much Grant (grtharris) or sending all these over.

And I thank everyone for their help so far - HERE IS THE LATEST:

Firstly the location photograph (Q-206.pdf) helped me enormously to actually find the electric brake controller connector (C210) that was Ford fitted on the chassis build. What a help and such a good image. It showed that the connector was not only nowhere near the steering column, but it was high up next to the bulkhead wall far behind the back of the instrument panel, and then behind a big cable loom there. I was so relieved that there was a connector at all.

That connector does have the green, brake switch "pedal depressed" signal cable, along with the others (exactly as per your document C210 connector.pdf)

Now, onto the issue that still exists. The E2IEN02E.pdf wiring diagram of the brake switch itself states "F53 '02" at the bottom of the page, so that was encouraging.... however this is what I found that baffled me:

From that diagram, I zoomed into the area showing the cable color configuration to pins of that pedal brake switch connector on that original E2IEN02E.pdf (see below):



HOWEVER, I photoshopped that diagram to show what my cable configuration is on the same switch (below):



As you can see, there is a difference between the diagram configuration and what I have. The pins 2 and 4 are switched over, and pins 1 and 5 are switched over. From the top of the plug (as its pins are in a single line). See below:



Hence all the different multimeter readings I discovered shown in the thread above. Also, that light green cable on Pin 2 DOES go to the C210 plug, and therefore as expected, the same multimeter readings apply here too: PIN 2: LIGHT GREEN: when brake pedal depressed = 12V HOT; brake pedal NOT depressed = directly to GROUND (which will fry the electric brake controller, as stated above in the thread).

Then I realized that the RED with LIGHT GREEN Cable (pin 4) in above image has exactly same readings: when brake pedal depressed = 12V HOT; brake pedal NOT depressed = directly to GROUND.

This did not make sense, going by the internal circuit diagram of the brake switch (below)...



So, I disconnected the plug and did a continuity check between the particular pins on the switch that the switch contacts affect (i.e (pin 5 to pin 4 and pin 3 to pin 2). The diagram states:

- at contact position 1 (brake pedal depressed) = contacts pin 5 to pin 4 are CLOSED CIRCUIT; pin 3 to pin 2) are CLOSED CIRCUIT
- at contact position 2 (brake pedal up/NOT depressed) = contacts pin 5 to pin 4 are OPEN CIRCUIT; pin 3 to pin 2) are OPEN CIRCUIT

HOWEVER, on this fitted switch I have on this motorhome, I discovered that the two contacts do THE OPPOSITE, as follows:

- at contact position 1 (brake pedal depressed) = contacts pin 5 to pin 4 are OPEN CIRCUIT; pin 3 to pin 2) are OPEN CIRCUIT
- at contact position 2 (brake pedal up/NOT depressed) = contacts pin 5 to pin 4 are CLOSED CIRCUIT; pin 3 to pin 2) are CLOSED CIRCUIT


So the whole set up seems to be back to front and upside down.

The Brake pedal switch Part Number on the side of the switch is F87B-13480-AB, yet Ford stated that that number is no longer relevant and that Part Number F87Z-13480-AA is its equivalent now (and used on many Fords up to 2011).

Either way, the only conclusions to are one or some of these:

1. This diagram for the Ford F53 '02 does not reflect what my F53 2002 has. OR...
2. It is the correct diagram BUT the Switch was the wrong one and so Ford switched the cables round to get the brake switch dependent circuits to function correctly (not realizing that they were affecting the brake signal Light Green cable for electric brake controller use). OR...
3. The Switch is faulty - (However, if I fitted a new switch (Part Number: F87Z-13480-AA) and it operated as per diagram of the internal circuit in the switch, then some of those brake switch dependent circuits might not work correctly because the way the brake switch connector has been wired. If I switch those cables around in the brake switch connector to match the diagram for the new brake switch, I am not sure that the circuits on those colored cables in my rig match those on the diagram because a few of these findings just don't match up with the diagram.)

There must be many of these out there (not just F53) because when I looked online for the Part Number F87Z-13480-AA switch and the other Part Number F87Z-13480-AA switch, it suggests these are fitted to a huge range of vehicles:

Up to 2011 in most of these: Mercury, Crown Victoria, Excursion, Explorer, F150, F250, F350, F450, F550, Ranger.

- - - - -

ALL comments and solutions greatly welcomed. Does anyone or anyone you know have a Ford with the F87B-13480-AB brake switch that can tell me what their pins give when connector disconnected? THANK YOU ALL!

[Miles F]

To add to the above, I had thought of another possible solution.

What we know so far:
We know that an electric brake controller requires a 12v +ve signal to red “brake signal” input cable. And, as per the electric brake controller instructions, when the brake pedal is NOT depressed, that brake controller red cable must be open circuit/dead (NOT GROUND) in order to protect the electric brake controller itself.

We also know that, having now found the Ford factory fitted brake controller connector (C210), that the Light Green cable runs from the brake pedal switch to that brake controller connector (C210).

POSSIBLE SOLUTION:
What if I bought a relay that worked off the Light Green cable in connector C210, such that when the brake pedal is depressed, the 12v +ve on the Light Green cable energizes the relay, closing a set of contacts to which I connect a fused 12v +ve (always live) cable on one side and the other side to the brake controller red “brake signal” cable which activates the brakes.
Then when the brake pedal is NOT depressed, and the Light Green cable goes to GROUND, that de-energizes the relay and causes the necessary open circuit on that relay contact in order to 1. Shut off the trailer brakes and 2. to safeguard the electric brake controller.

My understanding, from my memory of relays, that the relay coil will not be damaged by having GROUND on both sides of it in the brake pedal NOT depressed state.

Any thoughts?

[l1v3fr33ord1]

Miles F-

Hmm...

I put a great amount of stock in the wire colors matching the circuit functions. It should be easy to test the:

- ground (circuit 1203, black/light blue),
- first 12V supply (circuit 10, light green/red), and
- second 12V supply (circuit 18, light blue/black)

by pulling the fuses one at a time for circuits 10 and 18. This will confirm the circuit positions for the plug (brown) side of connector C278.

Let us know what you find.

In contrast, Ford's part numbering scheme is a big mess. Don't spend a lot of time trying to figure that out, or to use it as a troubleshooting tool.

[grtharris]

Miles F, OK after looking at your picture and some more drawings and a part picture of which on is attached.
My SWAG is someone swapped the two outside wires 1 to 5 and 2 to 4 to get the chassis stuff to work. Don't know how the brakes lights are working. If you look at the green and green/red that should be on the other side.
Attached is a good picture of a F87B-13480-AB I found.
Can you see the part number on your brake switch?
After more looking if it was mine I would pot that brake switch apart and see what the contracts look like.

[Hikerdogs]

We went through a similar situation with our 2001 Adventurer on the F53 chassis. It was an absolute PITA to find the harness connector under the dash. In our case it was taped to the steering column, but under one of the looms for the AC and heater controls. The plug itself was not visible.

As for the harness to the trailer plug the Ford factory supplied section ends just behind the left rear axle inside the frame rail. From there Winnebago adds the wiring and the 6-pin socket. Winnebago did not hook up the wire for electric brakes unless the option was ordered by the dealer.

The electric brake wire in the Ford factory harness is a #10 blue wire that is folded back and taped at the end of the factory supplied trailer harness. That wire has to be extended to the trailer socket.

We used a Tekonsha Prodigy controller and a Tekonsha supplied jumper harness to connect to the plug under the dash. It was a plug and play installation once we found the plug under the dash and were alerted to the fact that we had to extend the #10 blue wire for the electric brakes.

I used the same controller in our 2010 Ford Expedition and our 2013 Winnebago Adventurer. It was a much simpler installation in the later vehicles because the plug was visible under the radio and they both came with 7 pin trailer harnesses with the electric brakes already wired to the socket.

The sad fact is that most of this information has been lost. You would have to be a 24+ year veteran with the company to have encountered these situations. In either 2003 or 2004 and again in 2012 the wiring harnesses on the F53 changed. I'm sure they've changed since then.

[l1v3fr33ord1]

By the pictures, the switch and brown plug are keyed. This (usually) precludes reversing the plug when inserting it.

The E2IEN02E.pdf wiring diagram (Grant Harris, post 7), the plug wiring picture (Miles F, post 8) and the brake switch internals picture (Grant Harris, post 11) match perfectly for wire color, wire size and physical position on the switch. This means everything is built the way Ford designed it. The tests I propose in post 10 should confirm this, as well as the fact (if it's correct, that is) that the brakes and brake lights are working on the coach.

What does not match are the numbers on the switch housing, compared with the E2IEN02E.pdf wiring diagram. They are reversed.

My experience says that as long as the numbers on the switch are the only anomaly, and the switch and brakes work as designed and built, then one may note the anomaly but otherwise ignore it, for now.

I realize this doesn't get to the heart of the original symptom reported- of a brake signal, instead of reading 12V, being ground. But, if we can all agree that the switch and its wiring is exactly as Ford ships it, and as shown on the E2IEN02E.pdf wiring diagram, we can move on from that line of investigation and investigate the reported symptom.

I'd go on with suggestions in that vein, but hesitate to do so until we agree the above seems to be a correct- or, a most-likely correct- conclusion. And, I'm waiting for the results of the tests listed in post 10.

As always, and more frequently than I would like, I could be incorrect.

[Miles F]

REPLY THAT COMBINES ALL YOUR ANSWERS TO ABOVE POSTS: 9, 10, 11, 12 & 13

THANK YOU ALL FOR your input here. It has been so valuable and greatly appreciated.

PLEASE READ ON CAREFULLY AS THEIR IS A LOT OF DETAIL HERE (some repeated):

Here are some excerpts from your messages and any answers I have to clarify the details and over view of all this:

l1v3fr33ord1 post #10:

• I put a great amount of stock in the wire colors matching the circuit functions.

I have to trust the diagrams too.

• - ground (circuit 1203, black/light blue),
  - first 12V supply (circuit 10, light green/red), and
  - second 12V supply (circuit 18, light blue/black)

I did this test you suggested in post #10, from the ORIGINAL FORD BRAKE SWITCH AND WIRING DIAGRAM (E2IEN02E.pdf - post #7 by grtharris - thank you!) to confirm which cable colors match which circuits, and the test results are below:

TEST RESULT:

• BLACK WITH BLUE STRIPE: GROUND all the time
• LIGHT GREEN WITH RED STRIPE: 12V HOT all the time
• LIGHT BLUE WITH BLACK STRIPE: 12V HOT all the time (From FUSE 8 [mini blade fuse] in the BATTERY JUNCTION BOX [BJB] in the engine bay)

I have also confirmed (having first DISCONNECTED the Brake Switch Connector 278 and with the Ford fitted Brake Controller loom connector C210 already disconnected, that the LIGHT GREEN (LG) cable at connector C278 DOES go to connector C210.

So, with those 4 cables tested so far (Black/Light Blue, Light Green/Red, Light Blue/Black, Light Green) to establish their circuits, and even with the only remaining untested cable circuit (Red/Light Green) I can assume/trust that those cable colors and circuits match the original diagram (E2IEN02E.pdf).

NOTE: REMEMBER from my post #8, that 4 of the pins in the brake switch connector 278 on THIS RIG are not as in original wiring diagram (E2IEN02E.pdf). The pins are switched over: pin 2 is switched over with pin 4, and pin 1 is switched over with pin 5.
For a visual, I photoshopped the wiring diagram so as to match the configuration on THIS RIG, which highlights which cable colors go to which pins on the Brake Switch connector C278:


Image: CURRENT RIG (motorhome) CABLE/PIN ORIENTATION at Brake Switch Connector C278:



Below are my test results (already carried out in my post #4) where I have clarified the pin numbers I have put the pin numbers below AS PER CURRENT set up on this rig (as per wiring diagram image above:

TEST RESULTS WITH Brake Switch Connector 278 CONNECTED:

• PIN 1: LIGHT GREEN WITH RED STRIPE (LG/RD): 12V HOT all the time
• PIN 2: LIGHT GREEN (LG): brake pedal depressed = 12V HOT; brake pedal NOT depressed = directly to GROUND
• PIN 3: LIGHT BLUE WITH BLACK STRIPE (LB/BK): 12V HOT all the time (From 10Amp FUSE 8 (mini blade fuse) in BATTERY JUNCTION BOX (BJB) in engine bay)
• PIN 4: RED WITH LIGHT GREEN STRIPE (RD/LG): brake pedal depressed = 12V HOT; brake pedal NOT depressed = directly to GROUND
• PIN 5: BLACK WITH LIGHT BLUE STRIPE (BK/LB): GROUND all the time

grtharris post #11:

• My SWAG is someone swapped the two outside wires 1 to 5 and 2 to 4 to get the chassis stuff to work

Yes, that was my conclusion also, as in my post #8. And I see why they might have done so - read on...

• Attached is a good picture of a F87B-13480-AB I found

Firstly to answer your other question, yes, "F87B-13480-AB" is the same number on the Brake Switch in this rig. AND secondly, looking at the physical switching action shown in your photo of the cut open Brake Switch, it looks like the contacts that actually move are the rods on pin 2 and 4.
(I checked that as this switched is laid on the table, the pins go from left to right: 5,4,3,2,1).

On this switch:

DEPRESSED:
Pin 4 to Pin 5 = OPEN Circuit
Pin 3 to Pin 4 = CLOSED Circuit
Pin 3 to Pin 2 = OPEN Circuit (because there is never contact between them)
Pin 1 to Pin 2 = CLOSED Circuit

NOT depressed (i.e. in current position):
Pin 4 to Pin 5 = CLOSED Circuit
Pin 3 to Pin 4 = OPEN Circuit
Pin 3 to Pin 2 = OPEN Circuit (because there is never contact between them)
Pin 1 to Pin 2 = OPEN Circuit


HOWEVER, in the internal circuit diagram of the Brake Switch in the original Ford wiring diagram (E2IEN02E.pdf) it is the OPPOSITE - as below:

Wiring diagram (E2IEN02E.pdf) of switch:

DEPRESSED:
Pin 4 to Pin 5 = CLOSED Circuit
Pin 3 to Pin 4 = OPEN Circuit (because there is never contact between them)
Pin 3 to Pin 2 = CLOSED Circuit
Pin 1 to Pin 2 = OPEN Circuit

NOT depressed (i.e. in brake pedal up position, wiring diagram contact position "1":
Pin 4 to Pin 5 = OPEN Circuit
Pin 3 to Pin 4 = OPEN Circuit (because there is never contact between them)
Pin 3 to Pin 2 = OPEN Circuit
Pin 1 to Pin 2 = CLOSED Circuit


CONCLUSION:
The Brake Switch in the original wiring diagram is NOT the same switch fitted in this rig! This is confirmed by the meter readings from my test - for instance specifically, looking at my revised diagram above to match this rig, the following results I got for the LIGHT GREEN (LG) and RED WITH LIGHT GREEN STRIPE cables make sense:

• PIN 2: LIGHT GREEN (LG): brake pedal depressed = 12V HOT; brake pedal NOT depressed = directly to GROUND
• PIN 4: RED WITH LIGHT GREEN STRIPE (RD/LG): brake pedal depressed = 12V HOT; brake pedal NOT depressed = directly to GROUND

This conclusion is all considering these 2 factors:

1. the switch ACTUALLY fitted to this rig (Part Number: F87B-13480-AB) has a different configuration to the wiring diagram.
2. the Brake Switch connector C278, pin 2 is switched over with pin 4, and pin 1 is switched over with pin 5

I understand why 2. above has been done (pins switched) because that is the only way, with the current switch fitted, that the circuits on cables LIGHT GREEN (LG) and RED WITH LIGHT GREEN STRIPE (RD/LG) would get the 12V power needed


Moving on...

l1v3fr33ord1 Post #13:

• What does not match are the numbers on the switch housing, compared with the E2IEN02E.pdf wiring diagram. They are reversed.

I agree with everything you said in post #13 (and the test you suggested confirmed the cable colors to circuit numbers). However, the above conclusion I came to (in orange) is backed up by the fact that, if you look at the photo I inserted in post #8, on closer looking, the black tape on the looming of Brake Switch connector C278 looks rewound slightly compared to other looms that meet at a connector - one example of many on my rig is the Brake Controller, Ford factory fitted connector C210 which I final found (photo below):



So it looks like, somewhen in the last 20 years, someone changed the Brake Switch with part number F87B-13480-AB and then had to disconnect the plug, loosen the cable wrap, and swap over the pins as noted above to get the circuits to work. That is why the numbers on the brake switch housing look reversed (but this seems to be a completely different switch to that in the wiring diagram). Yes, grtharris, how the combined turn signal and brake lights work is a mystery (only that a switch from a 12V supply over to a ground applied to one side of a light bulb when the other side is to ground also, won't damage it).

TWO CONCLUSIONS FROM ALL OF THE ABOVE:

CONFIDENT that the cable colors and their circuits match the original wiring diagram (E2IEN02E.pdf), I would have to trust Ford to send me a replacement Brake Switch with the correction configuration/switching action - (one Ford parts employee said that Part Number F87B-13480-AB is no longer valid and its new allocated part number is F87Z-13480-AA, but I will not be convinced until I repeat the contact position test on a new switch of that part number F87Z-13480-AA to confirm it matches the original wiring diagram (E2IEN02E.pdf) and THEN I would switch back the pins 2 with pin 4, and pin 1 with pin 5 to ensure all those circuits work, AND that the LIGHT GREEN (LG) cable is DEAD/OPEN CIRCUIT when the brake pedal switch is NOT depressed.

HOWEVER - my wife and I live in this rig (currently at a remote campground) and looking at the circuits this Brake Switch affects, getting this right is essential because I have to start traveling in about a week. Time is short and the rig must remain drivable.

The only other "alternative" solution I can think of (at least until I am confident of a geographical location I would correct this set up) is the one in my post #9 - clarified as follows:

FIRSTLY - remember from my post #4, that because I could not originally find the factory fitted Brake Controller connector C210 (which has a 12V always hot cable, and the blue Brake Controller out put cable to the trailer brakes) I have already wired/loomed a completely new blue 10 gauge cable from the rear hitch 6 pin connector all the way to the dash board area to crimp to the Primus IQ Brake Controller wiring harness (which comes as four bare wires for the vehicle side - blue, red, white, black), and I also have already wired/loomed a 10 gauge 2 wire cable (red: 12V Direct from Battery with 20A Auto-Reset circuit breaker; black: battery -ve (Ground) to the dash area - thus all three new wires ready to crimp to this Primus IQ harness. Therefore, having now found factory fitted Brake Controller connector C210, I can use it for the LIGHT GREEN (LG) cable input signal I require. Hence...

ALTERNATIVE SOLUTION:
Objective: Utilize an Electric Brake Controller while at the same time safeguarding it.

Use a RELAY and use 2 of the pins in the factory fitted Brake Controller connector C210:

1. LEAVE all connections as they are at the Brake Switch

2. Get a relay, connecting:

• terminal 30 to the 12V hot all the time, fused cable in connector C210 (12V supply side brake for controller).
• terminal 85 to ground (in connector C210) for relay coil ground.
• terminal 86 to Light Green cable in connector C210 (for relay source to energize relay coil and close contacts when brake pedal depressed).
• terminal 87 to the Brake Controller RED cable (for the required brake applied signal).

RESULT OF THIS PROPOSED SOLUTION:
When the brake pedal is depressed, the 12v +ve on the Light Green cable energizes the relay on terminal 86, closing a set of contacts to supply the hot all the time, fused 12v +ve cable on terminal 30 to the brake controller red “brake signal” cable on terminal 87 (which then activates the trailer's electric brakes).
Then when the brake pedal is NOT depressed, and the Light Green cable goes to GROUND, which will not damage a relay, it will still de-energize the relay and will then provide the DEAD/OPEN CIRCUIT to the brake controller red cable (shutting off the trailer brakes and safeguarding the electric brake controller).

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I am conscious that this alternative solution would add in yet another circuit action to get that brake signal, so if anyone agrees with the first solution of a new (correct) brake switch and reconfiguration of the brake switch connector C278 pins to match the original wiring diagram (bearing in mind my need for a drivable rig) or has a better alternative solution to mine, I would be all ears and truly grateful to hear it.

Bless you all and THANK YOU!