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Czar Of Poop · 10-28-2018, 08:16 PM

Our back up lights stopped working (Maybe A Fuse) after I degreased the engine and got everything really wet. The back up lights work as part of the docking lights but will not come on when your in reverse. DW said that they came on for a moment while I was backing up but then went out like a fuse had blown.
Does anyone know where the fuse might be located in the engine compartment or where it might be located? Thanks in advance

K7JV · 10-29-2018, 06:53 AM

Try your rear run box, most likely in the mid to upper P/S corner of the rear opening of your engine compartment. It should be on board #2 which should be the top right circuit board in the box. On our coach, it is a little hard to get your head in to see the markings on the info strip. You should see three fuses on that board. One is by itself, and the other two are side by side. The one you want will be the left one of those two. I think it is a 10 amp.

Good luck!

Czar Of Poop · 10-29-2018, 04:40 PM

Hi Jim & Angie,
Thanks for the info. I checked and found the fuse as you described but the fuse was still good and tested good. So we are still looking. What confuses us is the fact that the back up lights come on as part of the docking lights. Thanks again for your thoughts.

K7JV · 10-29-2018, 08:23 PM

I just took a look at the schematic for the docking lights and some pictures I've taken of that area in our coach, and here's what I have gleaned. The relay just to the left of the 10 amp fuse you checked is the relay for the white lights on the back of our coaches. The circuit is designed so that the same lamps are used for both backing and for docking. That K2 relay has five connections on it. The numbers below are not the same numbers as any pin designations that might be shown on the relay, itself.

1) The coil for the relay is energized by the docking lights power when they are turned on. The power from the switch actually directly powers the four lights on the sides of the coach, and the relay to power what we would normally call the backup lights. This connection comes onto the circuit board on PIN 1 on connector J4, and is probably a #14 ORG/WHT wire. That terminal should show +12 V whenever the docking lights switch is turned ON, and should show 0 V when the docking lights are OFF.

2) There is a ground connection for the other side of the relay coil. My drawings don't show where that connection is actually made to the chassis ground.

3) This relay is what they sometimes call a FORM C contact, meaning there is a center terminal that is switched to one of the contacts when the relay is energized, and to the other when it is not. In this control system, the center contact of the relay is connected to the backup / docking lights on the rear cap of the coach. It leaves the board on connector PIN 2 on connector J4. One drawing suggests the wire(s) wlll be #14 RED/YEL, and another suggests #14 GRN. That terminal should show +12 V whenever the docking lights switch is on OR the ignition is on and the transmission is in the reverse position. (The engine may have to be running, but I don't know.) It should show 0 V when neither light function is selected.

4) The contact that is normally tied to the common terminal when the relay is de-energized is the power source for the Backup Lights. This comes onto the board on terminal J2, which is the left-most of three lug and nut terminals on the board. It is directly under the docking lights relay. The conductor is shown to be a #12 GRN wire. On our coach there are two wires connected to this lug, but I don't have any information to suggest what the second wire might be for. This terminal should show +12 V whenever the ignition is on and the transmission is in the reverse position. (Again, the engine may have to be running, but I don't know.) I would expect it to show 0 V when the backup lights are not being called for.

5) The contact that is normally tied to the common terminal when the relay is ENERGIZED is the power source for the Docking Lights. This terminal is not visible, as it comes from the 10 amp fuse on the board, and is fed from the primary 12 V source for all of the boards function. I think it comes onto the board on the middle of the three stud and nut terminals labeled J3 . This terminal should show +12 V most likely at all times.

My drawing shows a terminal strip TS-2 that is supposed to be mounted vertically, between board #4 and the Big Boy relay, but our coach does not have that strip. The drawings show that the power for the Brake Lights comes into the rear run box on the fourth terminal down, on that terminal strip TE-2. So if you have that in your coach, you can check there to see if Backup Lights power is available there, when the transmission is in reverse and enabled by the ignition and the engine likely running.

I'm sorry this post is so long, but their documentation is pretty fractured and I had to refer to a number of sources, including photos from our coach. I would first try to determine if terminal J2 is getting reliable voltage when your coach is calling for the backup lights. If it is, and the lights still aren't functioning properly, I would try rapping on the relay with the handle of a screwdriver and see if that has any effect. If it does, then the relay is probably your culprit. I don't envy you the task of pulling that board and replacing the relay if that is indeed the problem. If the power to that J2 lug is not reliable, then it is going to involve the circuitry from that point to wherever the device is on the transmission that provides the power, or the power source for that system from wherever else it might be, and I certainly don't have any documentation to get to that point.

Please share your success. You have quite the problem to solve. Good luck!!!

K7JV · 10-29-2018, 08:31 PM

By the way, that relay is a WJ107F1CS1212VDC.36. The contacts are rated at 12 amps and 125 VA or 25 VDC. The coil is 12 VDC. It is a CIT Relay.

YC1 · 10-30-2018, 12:11 PM

If there are relays as mentioned find one that is unrelated to the circuit and pull it out and put it in place of the suspected one.

Those relays do fail and are so cheap I bought a sack full.

It can be a real pain chasing something like this and not having a schematic. There might be a description on the inside of the fuse cover that shows what relays do what.

If you cannot sort it out then you can buy a cheap signal tracer and with that device you would connect the signal to the circuit in question wherever you can get to the wiring and then use the sniffer to follow the tone. My cheapie $20 "fox and hound" has save me hours.

K7JV · 10-31-2018, 06:48 AM

I hope you are right, Myron. Substitution is one of the easier and more effective techniques in troubleshooting. Unfortunately, on our '06 Dynasty, most if not all of them are soldered to the boards rather than pushed into sockets. No doubt they were hedging against them coming loose from road vibration. And with the exception of board #6 in the rear run box, board #2 is probably the hardest board in the coach to R&R.

I hope it isn't the relay that is his problem.

YC1 · 10-31-2018, 08:18 AM

Here is an example of a cheap signal tracer. There are better ones at Lowes and Home Depot and much more expensive ones for commercial use but this is one I bought and it has saved my bacon a couple of times.

You may be lucky and find a relay in a socket or a plug that needs some exercise. In any case, these can really help sort things.

When not in use just keep the batteries in a zip lock or tape them to the thing. Do NOT keep the batteries in them because they will be dead when you need them most.

Czar Of Poop · 11-02-2018, 08:52 PM

Hi Jim & Angie,
Thanks for the great info! Guess what? Now wait for it...………...That relay you pointed out to me that needed a rap on it with a screwdriver got gently rapped and now the lights are working again! Of course you have to hold your mouth a certain way when you rap. DW will be watching to see how long they stay working because she always helps me back up.
Again, thanks for everyone's info and helping out.

YC1 · 11-03-2018, 06:32 AM

Is that relay a plug in type? If so do yourself a favor and replace it.

A picture of it with a close up might show the part number and someone here will have a source.

$500 for hitting a relay? Ok, new bill. $495 for knowing which relay to hit.

K7JV · 11-03-2018, 08:07 AM

Yay! Glad you found the culprit!! Myron is right. It may never act up again, but relays seldom repair themselves, unfortunately. (I've got one like that in my front A/C unit!!) Dang! On our coach, the part number printed on the relay is WJ107F1CS1212VDC.36. It is a CIT relay. "J107F" is the series. "1C" means it is a SPDT (single pole, double throw) device. "S" means "sealed". The first "12" is the contact rating of 12 amps. "12VDC" is the coil voltage. And the ".36" is the coil power requirement of 0.36 watts.

Here is a link to Intellitec https://www.intellitec.com/index.php/contact

They are the manufacturer of that board, I believe, and I think they will be able to give you support. You should try Myron's idea and see if you can wiggle that relay and get it to come out of a socket. If so, replacement should be easy, once you find a replacement. If not, you are looking at the removal and reinstallation of that board, which on our rig would not be the least bit fun. Perhaps on yours it may hopefully be easier. You might try NW RV Supply or PPL in Houston to see if they might have what you need. I'm guessing they would have the board, but likely not the relay, by itself, but it would be worth a try.

Good luck to you!! And no charge on knowing which relay to "hit".