trailer wiring failed...where to look

[Stake Man]

This is on my 2004 1500 QC gasser. In October I pulled my trailer and everything worked. Last Friday I went to pull my trailer and nothing worked. I replaced the plug recpticle because a while ago I broke off the cover and thought this might be the problem(and I wanted to replace it anyways). But nothing still works. All the wiring looks good(it has a factory tow package, nothing spliced into it) and the brake controller shows a connection when the trailer is plugged in. But a manual application of the trailer brakes results in nothing. The controller shows voltage being sent out. So I connected the work truck up to it and everything worked fine and dandy. Re connected my truck and nothing. I tried a new adapter on the trailer wiring, nothing. I checked the fuses in the fuse box underhood and all was good.



Any ideas?



I don't want to take it back to the dealer because it is not out of warranty(in time, not miles). And I don't really have a lot of faith in the service department as a whole.

 

[JApol]

try out the info on this thread, it may help you out https://www.turbodieselregister.com...ons/193232-trailer-brake-elec-brake-woes.html

 

[Stake Man]

I know it is not the trailer wiring, it worked on this truck two months ago. It just doesn't work now

 

[JApol]

The truck and trailer wiring colors should be the same. You should have a variable voltage on the trailer brake wire when you push on the brake pedal. If you do have the voltage at the plug i would see about testing the voltage at the trailer brakes.



I havn't looked at trailer brakes since I could see over my socks so I don't know anything more about the trailer side of things. if you don't have the variable voltage at the truck side check the connections for your brake controller.

 

[MMeier]

You did check the fuses under the hood, correct?

 

[Philip]

If your controller is showing a connection it is most likely a bad ground.



Do a fast test. Take one side of a pair of jumper cables and hook it from the trailer frame to the truck frame. If everything works. Then all you have to do is find the bad ground and fix it.

 

[HBarlow]

I don't remember who makes it but someone in the RV/trailer parts industry makes a handy little plug-in tester that will quickly and easily identify the source of the problem you are having. It is a black plastic device, the size and shape of the male plug at the end of your seven wire trailer "umbilical" cord. You simply plug it into your truck's seven pin female connector and turn on the lights, flashers, stop/turn signals, or apply the brakes. A tiny little red light in the plug/tester will light to show you if power is available at the towing receptacle.



I bought mine at a trailer supply retailer that caters to RV transporters, Dan's in Elkhart, IN. I think it can be purchased at most RV dealers. Cost was about $20 and it can be carried in a door pocket or glove compartment.



Harvey

 

[jeepit]

If your controller is showing a connection it is most likely a bad ground.



Do a fast test. Take one side of a pair of jumper cables and hook it from the trailer frame to the truck frame. If everything works. Then all you have to do is find the bad ground and fix it.

I agree. I have found that 90% of the time it is a ground problem.

 

[steved]

You did check the fuses under the hood, correct?

Exactly what I thought... I popped the main fuse under the hood, and that kills ALL the wiring to the trailer...



steved

 

[Stake Man]

If your controller is showing a connection it is most likely a bad ground.



Do a fast test. Take one side of a pair of jumper cables and hook it from the trailer frame to the truck frame. If everything works. Then all you have to do is find the bad ground and fix it.

The controller is showing a connection, so I will try the jumper for ground test.



All the fuses underhood look and test(with ohm meter) good. After looking at the FSM wiring diagram, I see there is a PTC(circuit breaker?) somewhere in/under the fusebox. Makes me wonder if that hasn't reset if it popped.

 

[steved]

The controller is showing a connection, so I will try the jumper for ground test.



All the fuses underhood look and test(with ohm meter) good. After looking at the FSM wiring diagram, I see there is a PTC(circuit breaker?) somewhere in/under the fusebox. Makes me wonder if that hasn't reset if it popped.

I didn't think the circuit breakers came into play until 2006? My 2004. 5 has fuses... no breakers.



And your controller might show a connection, its only looking for a completed circuit in the braking system... not whether it has main power or not. Last I checked, there are five wires on the controller right... brake switch, power, ground, brake pos, brake neg.



I would not rely on the brake controller to tell me if things were working correctly (other than brakes)...



steved

 

[Stake Man]

I finally found the problem...

corrosion

corrosion in the plug and inside the adapter. Also found a mostly disconnected wire in the adapter when I was cleaning it. I decided to just replace the 6 way plug with a 7 way and trimmed the trailer wires back about an inch. All is good now. Thanks for the help.

 

[wcjp]

Dielectric grease