Troubleshooting Hazard Lights Not Working on Trailer Towed By RV

Updated 09/24/2019 | Published 09/22/2019

Products Featured in This Question

Optronics LED Trailer Clearance and Side Marker Light w/ Reflex Reflector - 6 Diodes - Amber Lens

(4193)

$13.82

Cordless Circuit Tester

(15)

$19.26

Question:

Hi I have a 28foot trailer that the hazard lights only partially work when hooked to our Gulf stream motorhome. When the trailer is hooked to our Dodge truck they work properly. Can you give me some ideas on how to fix this problem? Its a seven pin plug and all fuses and grounds appear to be ok. Thanks!

asked by: BJ T

Expert Reply:

By discovering that the trailer's hazard lights work perfectly when hooked up to your truck, you have at least narrowed down the problem area to the motorhome and know the wiring on the trailer is good.

The first thing I recommend doing is taking a circuit tester like # PTW2979 and testing each of the pins on the RV's 7-Way while you have the corresponding light function activated. I have attached a 7-Way wiring diagram to assist. If the brake/turn or running light circuit isn't getting any power with those lights on inspect the 7-Way itself for any corrosion or debris built up around those pins that needs to be cleaned out. This can sometimes prevent a solid enough connection with the trailer to ensure proper light functions.

If the connector looks good try and gain access to the wiring behind it and look for any frayed or exposed areas that need to be repaired/replaced. Make sure they are all still securely attached to the terminals on the 7-Way. Then from there it's really just a matter of trying to trace the wiring as far as you can, still looking for pinched/damaged portions along the way. You mentioned already doing this but just double check that all towing related fuses are in placed and in good condition.

If you continue to have this issue please let me know and we can keep troubleshooting.

expert reply by: Chris R