How to Troubleshoot Travel Trailer Running Lights Not working

Updated 01/27/2020 | Published 03/27/2017

Question:

Hi, we bought a 2017 31 ft travel trailer last weekend and after hooking it up to our Ford diesel all of the lights on the trailer worked. An hour into the drive back home we stopped to fuel up and I noticed that one of the trailers taillight covers fell off, but the light was still intact. At that time we noticed the running lights werent working, but the brake lights and turn signals were. We ordered from etrailer a Low Profile RV Combination Tail Light - Drivers Side - LED w/Black Base, and got it installed, but the same problem is occurring...no running lights. Every time my husband changes the running lights fuse in the truck and then turns the key, the fuse blows. Any suggestions? Thanks.

asked by: Nikkoal K

Expert Reply:

Since your trailer is brand new I suggest a visit to the selling dealer or to another authorized service/repair center. Small parts such as light lenses are easy to replace and inexpensive, but troubleshooting the blown fuse problem is not. Finding and correcting this problem is the dealer's responsibility (if the problem is indeed on the trailer side) but if you cannot do that then I suggest you test the truck's wiring, without the trailer connected, to see if you can isolate the source of the problem to either the truck or the trailer. If you have access to borrow another trailer for testing, you can find out if that other trailer has the same issue with your truck. If so, the issue is likely to be on the vehicle side.

If you have a circuit tester like # PTW2993 you can apply it to each circuit on the Ford's trailer connector, one at a time, to see if the correct light signals are present on the truck socket. Please refer to the linked article and the photo of an RV-style 7-way which shows the pin that carries the running light signal. The running lights are carried on the socket contact at the 11-o-clock position as you view the socket. Ground the tester and apply the probe to that contact while a helper turns on the truck lights. If the fuse blows, the problem is on the truck. If the fuse does NOT blow, and if you detect a 12V signal on the contact, then you know the issue is on the trailer.

expert reply by: Adam R

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Grant

1/25/2020

Outside upper clearance lights and both upper step porch light and upper porch light stop working . Both taillights and upper rear clearance as well as rear outside side markers working but nothing on front upper lower side and porch lights out . Once in a great while the upper right front clearance light might come on. Replaced all the fixtures and reconnected them no luck .

Jason S.

1/27/2020

It sounds like you have a ground wire connection issue. Often the fixtures use the mounting hardware as a ground, but there are times when a ground wire will need to be added to that hardware to give you a bare metal to metal ground connection so the lights will work properly. I recommend running a jump wire from your frame to the last light in your sequence. Attach that wire to your mounting hardware and it is likely your issue will be solved.

Helpful Links

faq-4-5-way-troubleshooting.aspx

faq-wiring-7-way.aspx

faq-wiring.aspx