Troubleshooting Tail Light Issues on New Grand Design Trailer

Updated 07/19/2024 | Published 12/15/2019

Question:

Connector on truck was tested and good. I did not have trailer attached at the time. Right back trailer light very dim and looks like it may be trying to flash but so dim it’s hard to see. Left back trailer light worked fine with turn signal, brake and flashers. Changed right bulb and now it works fine but the left one now stays solid. I have cleaned and checked all connections. Please help. There was some moisture in both taillight covers and I dried it out. Worked fine last time we used trailer.

asked by: Gayle F

Expert Reply:

Since you tested the tow vehicle's connector and know it's working properly, we can at least focus all our attention on the trailer side. It sounds like you've already done this, but it certainly sounds like there's some kind of ground issue on the Grand Design that's causing the dim lights, and now the issue on the left side tail light.

Check once more to make sure all your ground connections, both the main harness ground for the 7-Way and each individual ground for the light assemblies (whether they use a dedicated wire or ground through their mounting hardware) are securely attached to a clean, bare metal surface that's free of any debris or corrosion.

It might be difficult on a trailer like this, but your next step will be to try and inspect the trailer light wiring coming back from the connector and leading back to the light assemblies. Most of the wiring is probably pretty well hidden/covered but any sections you can access make sure there aren't any exposed, pinched, or otherwise damaged areas that need to be replaced.

If the issue persists please let me know and we can continue to troubleshoot.

expert reply by: Chris R

Rick

7/18/2024

Is there a short cut breaker or any fuses in the trailer wiring. This is a brand new grand design 3200.

Chris R.

7/19/2024

@Rick There certainly could be. I'd check the chassis owner's manual for fuse locations under the hood related to the towing/trailer light circuits and see if anything needs to be replaced. Unfortunately I don't have access to that info.