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SHutson · 01-01-2016, 01:28 PM

I have a new-to-me DP and it has an odd trailer wiring setup. It has a 7-pin socket (although not all the wires appear to be hooked up) where the tail, turn and brake lights all work correctly. In addition, there is a pair of flat connectors, a flat-4 and a flat-3. The flat-4 shows working tail and turns but no brake light power. Like an idiot I neglected to test the flat-3 for brakes because I thought it must be for some other purpose - I've never seen a flat-3 connector before.

Anyone have an idea what the flat-3 connector is for? Is it possible it carries the brake signal? If so, why?

TIA, Steve

l1v3fr33ord1 · 01-01-2016, 01:37 PM

Steve-

It would help us to know the year, make and model of your DP.

Old-Biscuit · 01-01-2016, 01:47 PM

Colors in () are 'typical/routine colors used for that function

7 pin.......
Right turn (Green)
Left Turn (Yellow)
Ground (White)
Tail/markers (Brown)
Brake (Blue)
Battery (RED or Black)
Backup (Purple)

4 pin.....
Right turn (Green)
Left Turn (Yellow)
Ground (White)
Tail/markers (Brown)

3 pin.........
May have been set up to tow Jeep

dennis45 · 01-01-2016, 02:03 PM

Standard configure for most hookups.

SHutson · 01-01-2016, 02:13 PM

It's a 2002 Discovery 37U, but I'm pretty sure the 7-pin is the OEM connection. The two flats look added on. I'm hoping I can cannibalize the two flats for a dinghy umbilical but I need to find a brake signal.

Old-Biscuit · 01-01-2016, 02:39 PM

One of the pins on that 7 pin will be for brake controller output

SHutson · 01-01-2016, 03:42 PM

It turns out one of the conductors (green) on the 3-pin is the brake light. The previsions owner must have had some odd, one-off trailer/towable wiring. I think I'll just remove the two flat connectors completely to keep from confusing the issue.

FIRE UP · 01-01-2016, 04:15 PM

Shutson,
Just wondering, what is your tail light arrangement like? I mean, in some Journeys and Discoveries of that era, there were Amber tail lights for turn signals and Red tail lights for brakes and tail/marker. Now, normally, in a situation like that, either the chassis manufacturer or the coach builder NORMALLY will combine those two into a "3 wire to 2 wire" tail light converter. And that converter is a small, approximately 2" x 2" x 1/2" box, wired up in the wires from the tail light to that 7-pin plug. And, those converters have been known to fail, not often, but they do fail on occasion.

So, what that means is, in your 7 pin plug on the back of the coach you should find:

1. Rt/brk combo pin
2. Lt/brk combo pin
3. Tail/marker pin
4. Ground pin
5. B/U (back up) light pin
6. 12V lead for aux power pin (for toad battery charging)
7. Trailer brake pin ( for towing trailers with electric brakes)

Now, it's pretty obvious that the other two plugs, both the 4-wire flat and 3-wire flat were add-ons. If you have no need for those two EXTRA plugs, I'd eliminate them from the picture so you have just the 7 pin plug to deal with. Now, normally, in the situation as I described above, either the right or left turn signal pins in that 7 pin plug, will also display a brake light signal when there is no turn signal being applied to that particular circuit.

In other words, if your turn lever is in the neutral position, and the brakes are applied in the coach, then you SHOULD be receiving a brake light signal from both the right and left turn signal pins in that plug. If you don't, then you've got an issue somewhere prior to that 7 pin plug.

Now, if your tail lights are ALL THE SAME COLOR then the tests I've just spoke of, will or should, reveal the same exact results. As for the wiring colors, that's been shown to you a few times so, you've got that already.
I don't know if any of this info has helped you or not but, let us know what you find out.
Scott

SHutson · 01-01-2016, 05:19 PM

Fire Up, I have amber turns, I hadn't thought of that but it may explain the supposed need for an additional flat connector by the previous owner. What you describe as correct operation is what I find with my meter at the 7-pin female socket. The 12v power and electric brake controller wires are dead (I didn't test the back-up wire) so I assume those were never hooked up. The flats will be removed. I think I have a 7-pin to flat-4 adapter somewhere so that is what I will use when I need a flat-4 connection (U-Haul, etc.). Thanks.

FIRE UP · 01-01-2016, 07:23 PM

Quote:

Originally Posted by SHutson

Fire Up, I have amber turns, I hadn't thought of that but it may explain the supposed need for an additional flat connector by the previous owner. What you describe as correct operation is what I find with my meter at the 7-pin female socket. The 12v power and electric brake controller wires are dead (I didn't test the back-up wire) so I assume those were never hooked up. The flats will be removed. I think I have a 7-pin to flat-4 adapter somewhere so that is what I will use when I need a flat-4 connection (U-Haul, etc.). Thanks.

Hey Sir,
So, if I understand what you just said correctly, you're saying that you DO have brake light signals, turn signals and running light signals at the appropriate pins in that plug, correct? And that your Electric brake signal, and 12VDC auxiliary power pin, are both dead, correct? The back up pin was not tested.

So, if all of your tests revealed all that all the correct signals at all the correct pins are working correctly, then you're good to go. At the moment, I cannot really think of a reason for separating some or, any of that wiring, and sending it to separate plugs for use in towing any form of vehicle and or trailer, that the stock 7 - pin plug, with an adapter, could not handle.
Scott

P.S. The 12VDC pin in that 7 pin plug, may or may not be connected or, it may or may not be activated with the ignition of the coach. It would behoove you to do followup tests to find out what's wrong (if really anything) with that particular pin. That way, in the future, if you determined you might need 12V to be sent to a toad battery while towing it, you'd know you already have it in place and, that it's working instead of maybe fixing it then, when your time might be more valuable in other areas at that time. Just a thought here.
Scott

P.S. 2, The Backup signal is rarely used. Heck, most people don't even have correctly working trailer lights, much less having actual working back up lights on a trailer. I need that back up signal to work on ours mainly due to the fact that it triggers a solenoid in our boat trailer to lock out the hydraulic surge brakes for backing the boat up hill.

As for the electric trailer brake signal, you more than likely know that, the only way for that one to work is to have a working electric trailer brake controller at or under your dash.
Scott