RV electrical question

[WAckerman]

Finally had the chance to hook up and take my new (to me) 5er out last night for a quick run around town. When I hooked up, I found out that the left rear trailer light wouldn't work for turn signal or brakes. Tail lights worked fine. Checked the bulb, but didn't see anything wrong. Bought new bulbs anyway and brake and turn lights still don't work.



So my question is, where do I start looking? We have a trip planned here in the next little while and I need to get this fixed!



Oh yeah, the trailer is an 04 Coachmen 281BHS.



Thanks guys!

 

[Slow Six]

Get a volt meter and check at the truck plug to see if there is current to there. It there is check the trailer plug and just keep tracing back to the light. Most likely a broken wire/loose connection.

 

[Loren]

WAckerman,



The wiring to your RV does not have separate circuits for the brake lights and turn signals. There are two circuits for this, one for right turn signal and one for left turn signal. When you apply the brakes, both lights come on.



Here's a document I put together quite some time back to help me keep track of what's what:







Trailer wiring codes:



Terminal number, Wire color, Recommended Gauge, Circuit



1, White, 10, Common ground

2, Blue, 12, Electric brakes

3, Green, 14,Tail, license, running lights

4, Black, 10, Battery charge (hot)

5, Red, 14, Left turn

6, Brown, 14, Right turn

7, Yellow, 14, Extra auxiliary (back up lights)





Looking at the receptacle on the truck, at the top is the keyway for the plug. There are three terminals to the right side and three to the left. This is the layout:



Upper right: #4 (black wire): Battery charge: This pin should always have battery voltage = 12. 6 volts.



Middle right: #6 (brown wire): Right turn: This pin should have zero voltage with the lights off. It should read battery voltage intermittently when the right turn signal is flashing. It should have battery voltage continuously when the brakes are applied. My previous truck (2000 Dodge diesel) read 11. 7 volts when this is powered.



Lower right: #2 (blue wire): Electric brakes: This pin’s voltage will vary with increased output from the brake controller. The Tekonsha Sentinel controller sends 0. 5 volts to this pin continuously. Voltage increases to battery voltage with full brake application.



Upper left: #3 (green wire): Tail and running lights: This pin should have zero volts when the lights are off, and battery voltage when the lights are on. Mine reads 0. 1 volt with the lights off. Not checked with the lights on.



Middle left: #5 (red wire): Left turn: Same as for #6, except for left turn signal.



Lower left: #1 (white wire): Ground: Should never have any voltage.



Center: #7 (yellow wire): Auxiliary pin: The travel trailer industry uses this pin as power to the backup lights. Dodge wires the factory receptacle that way. It should have zero volts when the backup lights are off and battery voltage when the truck is in reverse and the key is on, that is, whenever the truck’s backup lights are on. My truck reads zero with the lights off. Not checked with lights on.



Good luck.

 

[JMetzger]

What Loren gave you is great. The only other suggestion I would have is to check and see if that turn signal works on the truck. If it doesn't work on the truck your problem could be in the turn signal switch. Turn signals & break lights work through the turn signal switch.

 

[PBJ2500CTD]

Excellent posts by Loren, Slow Six, and JMetzger. If the voltages are all present on the truck's plug the next step should be to look carefully in the trailer plug to see if some critter built a nest in the affected pin. I have had spiders build their nest in mine, causing all sorts of odd indications. While you are looking into the socket insure that the connectors in the socket are not spread out too much. Then, if all checks good, disassemble the trailer's plug and look for corrosion and/or loose connections related to the affected circuit.

 

[WAckerman]

Thanks Guys! I'm going out to take a look at it now. I didn't think to look at the trailer plug itself, but I'm wondering if theres not something in there or some corrosion. I know when I first bought the trailer back in Oct. that I backed onto it and checked to see how much clearance I had between the bed and the trailer and all the lights worked at that time...



Thanks again, and I'll let you know what I find.

 

[icman95]

Also check for bad ground on the trailer. When we picked our up new at the dealership, we had a similar problem and turn out to be a loose ground wire in the junction box inside the pinbox. In other words, follow the trailer cable up to where it goes into the pinbox and you should see a silver colored electrical box. Our problem was a loose wire in there. Easily fixed once found.

 

[WAckerman]

well, I think I found the problem!



As a was following Loren's instructions I find that neither the factory plug on the bumper or the plug I added inside the bed have any voltage on the left turn pin (middle left pin, when the keyway is at the top).



So I checked the fuse box under the hood and found 2 burnt fuses. One 15amp and one 40amp. Replaced both of them and now I have blinkers on the trailer and my power seats are working again! Oo.



Thank you all for your help!