I don't have a left stop or turn, but the running lights work fine on that side, i have changed light assembly's but no difference, i think its coming from my truck, the fuses are all fine, any ideas?? i've had this problem with this truck on multiple trailers my truck didn't come from the factory with the tow package its a 97 f150, flat 4 connector

use a volt meter and check the connector on the truck to make sure. if it's bad there, check the connectors, also you may have 2 fuse blocks. I have one under the dash, and one under the hood. Get out the manual for a diagram of where that fuse is.

I had the same problem and it was a fuse

I just had an issue with my GMC where the brake light fuse was fine, but there was a running light fuse was blown. It took a while to find because they are in two different locations (one on side of dash, other under the hood). I expect that your F150 has the same setup as this link. You should be looking in a mini fuse box under the hood. <BR> <BR><a href="http://f150online.com/forums/showthread.php?t=325274" target="_blank">http://f150online.com/forums/showthread.php?t=325274</a>

I used to have an F-150. I had LED lights on the trailer, but for whatever reason they were not waterproof. I would blow a fuse every time I launched (even if I unplugged the trailer). It's a 15 AMP fuse under the hood. I went to AutoZone, and bought a package of them (couple bucks). After I replaced the light the second time, I didn't blow any more fuses. I got the lights from AutoZone too. Just told them they leaked. They gave me new ones.

had the same problem with mine last week. Changed the male adaptor that you plug into your truck so you can plug the trailer into your truck and works now.

I would use a tester on the 4-flat or 7way and if it is your truck then it is probably a fuse issue. If it is on the trailer side and you have power going to the lights check the grounds and make sure no rust has built up under them.

oK I'll check my fuses again, I tend to blow one when i launch and the lights are hooked up on my dads old jetboat trailer, but last time I checked the mini box under the hood and none blown in there, I'll check again, thanks for the help, <BR> <BR>maybe I have the same problem as miguel also, my male adaptor is getting pretty beat up....

Sorry to hijack your thread, but I have the same issue with my truck/trailer. I checked my lights with my travel trailer which is a 7 prong plug and my right signal light works just fine but on my boat trailer it doesn't work. The wiring/fuses for those 2 wires should be the same are they not? I have the same issue where my running light works, but no brake or signal light. Is there a seprate light that could be burnt out or is there just one light in those assemblies that just turns brighter when need be?

I had similar issues and after crawling under the boat for an hour to check all the wiring I figured out it was a fuse in my truck. Felt like an idiot but oh well, it was fixed. So I'm out at the local auto parts store and they were selling a plug adaptor, whatever you call the thing you plug the trailer lights in to, and it had lights next to each prong that lit up to tell you if it was getting power or not. Kind of silly, I know...but pretty easy to tell if it's the trailer or the truck now. Only cost a couple bucks more then your regular adaptor and would have saved me a lot of grief and my reputation with the neighbors. Anyway, just a suggestion.

The brake lights are a dual filament bulb. For running, one filament is on, use the brakes or turn signal, and the 2nd filament lights up. It's possible that you have a bad bulb where only one of the two filaments is still good. <BR> <BR>(Message edited by toneus on May 15, 2008)