I am having a problem with my trailer's lights. I know the problem is somewhere in the truck, because I have the same problem on multiple trailers. The problem is that the left brake light stays on, until you hit the brakes, then the left brake light goes out and the right one comes on. As soon as you release the brakes, the right light goes out, and the left one comes back on. The truck is a '97 F-150 with the factory towing package. I have checked all of the fuses and no problems there. Does anybody know if there is a relay for the trailer lights? If so, where is it? Anybody ever had a similar problem

 

This may sound goofy but try checking your tail and brake light bulbs on your truck. I've seen weird stuff happen when one or more filaments burn out.

Also, be absolutely sure that the ground connection on the truck side is clean and secure. Strange things happen when the ground comes loose and the return path has to come through the ball or a bulb.

 

Hi T5

The 98/99's have relay in main fuse box under hood. Dont know about 97, however.....

You may know, if not...take a close look at/around the fuse box under hood, look for another small fuse box, if there, i think it has fuses for the trailer lights etc.

If that dosent work, then gonna be trial/error.

Good luck...OT

 

no relays are involved with trailer lights, turn signals, or brake lights. very interesting problem. have you solved it yet?

 

Do you have a topper with a third brake light? If so, how do you have it wired?

If you don't have a topper, I always blame the "GROUND".

The relays for the tow package are for the trailer brakes.

Sorry I couldn't be of more help

 

one relay is also for charging a battery on a trailer if the trailer is so equiped. like a travel trailer.

 

Thanks for the replys everyone. I think I have found out what the problem is. I do believe that the problem is a bad relay. With the trailer hooked up and the key in the on position, I turned on one of the blinkers. I could clearly hear the relay clicking under the hood. I opened the hood and pin-pointed the realy. I switched it with the one next to it, and the trailer lights reversed. That is to say, the left brake light went out and the right one came on. When I hit the brake, the right one went out and the left one came on. Just the opposite before I switched the relays. Couldn't find any new relays around here, but everyone offered to order them for about $15 each. I bought 5 of them off of E-Bay for $7 shipping included. Still waiting for them to come in. I’ll make a post to let ya'll know if it works. Thanks again.

 

Thanks for the replys. The new relays finally arrived today. I plugged them in, hooked up the boat, and everything is A OK now. Thanks.

 

Thank you so much for posting this! I spent about 3 hours tracing lines for the same problem. I finally came across this post after searching for "reversed".