Help! Wiring issue with 1980 17.5 SB

[Stage Coach]

We recently purchased a 1980 17.5 SB - We are having an electrical issue. It appears that our running lights do not work. When we put on the blinkers, both lights flash. The clearance lights do not work (will not come on). We have tried locating a schematic and as you probably know, there are no schematics available that I can find. It is currently wired with a 4 prong connector to the tow vehicle, but according to the wire colors it appears that there was a 6 or 7 pin originally. Unsure, according to the wiring colors.
Does anyone have any suggestions?

[Sunline Fan]

Welcome!

Yes, your coach should have originally been wired with a seven pin for the electric brakes, but obviously the previous owner didn't want to wire his/her vehicle for them, so they just cut it out. Either this or the brakes just don't work, which is possible. I would make sure to go through these systems thoroughly and rewire a seven way plug on. When you do this, go to a dealer and get a long cord (like 8') with the plug molded on. Then, rewire the pigtail in where the old one connected.

As for the clearance lights, I'm guessing it has something to do with age. Assuming you have the lights I think you do, they don't take age very well. I would visit an RV dealer and get all new replacement fixtures (they should have the same style) and replace them all. The lenses always tended to crack and fall off, and then water would get into the contacts and corrode everything. If you try to clean the light, you'll probably just break it apart.

I have a feeling that once you do all that, you'll find it'll all work correctly again.

If you have any pics, we'd love to see them!

Good luck,
Jon

[Steve Collins]

Those clearance lights are industry standard fixtures, and can most likely be purchased at an auto parts store for a lot less money than at an RV dealer. I know I can get the Bargmann 68's that are all over my trailer at auto parts stores so it is likely that whatever clearance lights are on your '80 are available there, too.

If none of them are working, there is probably a bad connection break in the 12vdc line before it splits to go to the various locations around the coach. Obvious places would the be coach/tow vehicle connector itself, and then at the other end of the coach side pigtail.

Are you testing by plugging into your tow vehicle or jumpering the pigtail to a battery? If from the tow vehicle, double check to make sure that it is putting proper voltage at the connector at the rear of the vehicle. (I just hooked up our boat trailer to the Jeep for the first time this year, and nearly went nuts because none of the trailer lights would work. Then I remembered that the Jeep has to be running for the trailer light circuits to work! A little egg on my face, but no harm done.)

If you are jumpering the pigtail to a battery, are you certain that you're putting 12vdc down the correct line for the clearance lights? Is there a good ground back to the battery?

If individual clearance lights were out, check the bulbs, then the sockets (corrosion can cause real troubles here.) If you have a small multi-meter or 12vdc test probe, you can begin to troubleshoot the individual sockets or the entire system.

Are the turn signals working? If they are, that indicates that there is a fair ground and at least some of the 12vdc is going to the right places. If they are not working, time to double check ground for the entire trailer. That brings you right back to that modified pigtail where it all funnels into a single location.

On other thought... On a 28 year old trailer, it is possible that all of the bulbs are shot, so replace one or two of the bulbs first, making sure that the fixture has a good ground and that the socket is clean and free of corrosion. I like to put a very light coat of dielectric grease all over the bulb base and the socket of every fixture on my trailers. Prevents corrosion and keeps water problems to an absolute minimum.

[Lode]

I'd think if you've got signal/brake lights your ground is doing its job. Your running/brake/turns should be grounded off of the tow vehicle's ground send through the plug, not the trailer's battery ground.(although if trailer battery ground is bad, your electric brakes won't work, but that trouble shoot would come by getting rid of the 4 prong and using a 7 prong pigtail and getting the brakes working, which you really should have anyways) The running lights are daisy chain run, or series, so once you find where the break after pulling the lense and unscrewing the light base to expose the wiring, either ground or (+), you'll be in business till the next break. You'll most likely encounter a corroded wires at the connection points to the running lights. You can either use a running light you know has a working bulb, a multi meter, or a test light to trace where the chain starts and ends. I'd think even with the rigged 4 prong, you should have running/left turn-brake/right turn-brake/and ground currently spliced to your TT lights. The other 3 that aren't in use are your brakes, reverse, and a (+) send to the TT to the battery on the tongue of the TT to trickle charge it. (There should be a fuse before it hits your battery's (+) and if your battery isn't properly charged, it'll blow this fuse before getting to your TV's battery system... the battery is used to power the TT electric brakes.

On my 92 TT the run goes to TT door side front marker, then to my upper left marker if you're facing the tongue end of the TT and runs right, down around the corner to the marker near the cargo storage, back the trailer's utility side to that light, and to the driver's side brake light. From here it's split up to the clearance marker's along the top back and another run inside the wall near the rear bumper of the trailer to the other brake light and then to the marker off that corner on the door side. The turns/brake wiring goes straight back the utility side of the trailer to the rear brake lights and rejoins the running lights at the driver's side brake light.

When I bought mine this spring, I wanted all new marker/brake lights with LEDs to rid the blown bulb worries. I removed, respliced/replaced in the order I just described and everything worked properly when I got to the end. I was also able to ensure that the connections on each light are weather/corrosion proof before reattaching the bases... done messing with them for my lifetime, I hope.

I bought my markers for my TT, both ambers and reds, at Walmart. They're near the hitches/towing section in automotive. If you're looking for an exact match, search around online, I'm sure you'll find it. I found an exact match LED lights to my 78 Sunline truck camper's markers at wally world this weekend.

Here's a site that has the color codes for trailer wiring.
http://www.marksrv.com/wiring.htm

Hope that helps get you on your way to getting your lights up and working.

Take care,
Jason

[frank]

Originally Posted by Stage Coach

We recently purchased a 1980 17.5 SB - We are having an electrical issue. It appears that our running lights do not work. When we put on the blinkers, both lights flash. The clearance lights do not work (will not come on). We have tried locating a schematic and as you probably know, there are no schematics available that I can find. It is currently wired with a 4 prong connector to the tow vehicle, but according to the wire colors it appears that there was a 6 or 7 pin originally. Unsure, according to the wiring colors.
Does anyone have any suggestions?

*Assuming* (and that's a big assumption) that whomever converted it to a 4 pin connector did it correctly, it sounds like it may be a bad ground. Try temporarily connecting the trailer frame to the vehicle frame and see if the running lights and turn signals work correctly. If so, you need to rectify that ground issue. This is also assuming you want to keep it on the 4 pin connection.

Now if you want to get those brakes working again, then Jon is on the money. The easiest solution will be a replacement 7 pin pigtail..

- Frank

[Stage Coach]

I want to thank everyone that responded so quickly. I believe that the information and tips provided will get us on the right track. I will post a picture of the camper as soon as possible. We are doing renovations and will post pictures along the way.

Stage Coach