OT Trailer wiring problem

nhproxr · February 23, 2005

I have a '01 snopro v-nose enclosed snowmobile trailer and I'm having wiring problems. Trailer lights worked fine with my '98 Yukon when got trailer. Sometimes my buddy tows it with his '99 super duty Ford. When he does the left directional/brake light will not work. Then I plug it into my truck and that light doesn't work with mine either. I traced back wiring and its all good, I replaced connector at light, then simply played around with connection to light and made sure no corrosion. Plugged truck in and left directional/brake light work again. This past Sat we used his truck to tow again. Last night I plugged into trailer again and left diretional/brake light out again. WTF???

Also super duty has separate fuses for trailer wiring functions. The first time it popped the fuse for left directional/brake light, this past Sat he claims fuse was good.

mcreyaufmiller · February 23, 2005

Check for a ground problem at the lights and at the hitch.

willieboy · February 23, 2005

It definitely sounds like a bad ground somewhere. And, it is likely with the actual light itself, because if it was the common ground none of the lights would work properly.

nhproxr · February 23, 2005

But isn't it strange there seems to be no problem when my truck is hooked up, just my buddies F250?? Is there some ground on his truck that could be bad, maybe a short in that trailer wire on his truck?

asilverblazer · February 23, 2005

But isn't it strange there seems to be no problem when my truck is hooked up, just my buddies F250?? Is there some ground on his truck that could be bad, maybe a short in that trailer wire on his truck?

<{POST_SNAPBACK}>

Do you hear what you're saying "But isn't it strange there seems to be no problem when my truck is hooked up, just my buddies F250??".

It's a Ford. No, it's not strange. Also Chevy's have seperate trailer fuses or the 99's and up do.

nhproxr · February 23, 2005

I know that is what I keep telling my buddy !!!

I don't believe I have separate fuses for trailer wiring, at least I've never seen it. Think that started with NBS trucks.

Yukon04 · February 23, 2005

Remember...the bulbs are directional! I have seen this issue many times, and in some cases works, then doesn't work, then works, etc.. Check and make sure both bulbs are in correctly.

There are tangs on the bulb housing, one high and one low. The bulb socket has corresponding high/low slots for the tangs.

Seems dumb, but I can't even count how many people I've shown this too.

If bulbs are in OK, 99.9% of the time it is a bad ground at the connection. Check it twice...

There are trailer connector checkers (for lack of knowing the proper name). You plug into the truck connection and it has 3-4 bulbs that correspond to brake, turn, etc.. it will allow to verify that the truck wiring is good. Most trailer shops have them. $1-3, cheap tool

nhproxr · February 23, 2005

Trailer uses sealed tail lights, when one light goes you throw out the whole thing and replace it. There is simply a plug in the back for the wiring. Same sealed tail light that all newer tractor trailer trailers use.

willieboy · February 23, 2005

If it is only with the F250, then it is the truck that has a bad ground or a wire short. I would check the wiring harness first. Does he have other trailers he pulls? If so, check to see if they have the same issue. It may be that your trailers connector does not seat right in his trucks connector. We had that happen on a boat trailer. Turned out the truck side had a broken pin, but it looked fine from the outside. It was not until we took the connector apart we saw the problem.

71GMC_3/4T · February 23, 2005

Does the furd have some sort of grunge or something on one of the pins that's transferring to your plug and causing an open?

There are several different ways to wire up trailer plugs, but usually they cause the electric trailer brakes to not work, or be full on.

nhproxr · February 24, 2005

We just put on a new 7-way plug on his truck this past fall (stupid ford doesn't even come factory with that!!) so I would think he is good. I would assume it was just his truck except for the fact after it doesn't work with his, it doesn't work with my Yukon until I fiddle with the wiring a little.