Trailer Lights

[dirtyone55]

I have a trailer that is only 2 years old. My problem is that the brake lights, and the turn signals do not work. The running lights do work, and I am pretty sure it is all grounded correctly. The trailer was bought new with the wiring already done, and working fine, but one day somebody noticed and told me that the lights were not coming on. I tried following the wires to see if there was a break anywhere but most of the wires are rand through the frame of the trailer and not visible. Does anybody know of a quick wasy to check and see where my problem is located possibly with a multimeter or something of that nature? Any help would be greatly appreciated.

Thanks

[IWRBB]

Check the groundwire on the trailer side of the plug, it's white. It should be attached to the trailer. After years of fighting trailer lights though, I can tell you it's likely damaged wires inside the trailer. They yank the wires though the inner frame which has welding slag and rough cut holes, which in turn strips parts of the insulation off.

The best thing to do is re-wire it. It'll take a couple hours if you have running/clearance lights, less than an hour if you only have the 2 rear lights. Use the existing wire to pull the new wire. Twist, solder, then heat shrink every connection. Make sure the new white ground wire is getting a good connection to the trailer and it's protected from damage.

[dirtyone55]

if the ground wasn't grounded, wouldn't the running lights not work?

[Black Horse]

East way to check everything is with one of those 12v light setups or a volt meter. Just start at the plug and work your way back. Sometimes there are junction boxes that get full of crap and not let the continuity continue!

Those 12v test light setups work well if the pointy end if real sharp - you can poke through the insulation to test the actual wire and work your way along.

Some trailer ground through the ball hitch too....if there is a question about that throw a jumper cable between your truck frame and the trailer frame.

Just take your time and use lots of patience and you'll find the problem. I dont know why, but trailer wiring is always a pain in the arse.

[IWRBB]

The ground wire can be intermittant, ours was on our boat. The crimp on spade connector wasn't crimped on that well.

I'm telling you man, you can dick around checking this, testing that, patching this, taping that... or you can just pull new wires and know it'll work for years to come. I've done both and there's only one way to go if you plan to keep the trailer. A pre-wired trailer harness is dirt cheap too.

[dirtyone55]

I never heard of the whole grounding through the hitch thing, but I guess you learn something new every day.

Like I said, I really dont think it is a grounding issue since the running lights do work. is there a way I could start off at the connection harness at the trailer and check continuity or see if there is a short just to maybe save a little bit of time?

[Black Horse]

12v test light or volt meter!

[Jeff88coupe]

Yep..trailer wiring can be a pita. After a few years of patching my open trailer's light wiring to keep it working I finally just bought a whole new wiring harness/light kit from Harbor Fright...$20.

[Byrd Man]

I have a link for a Ford truck wiring diagram that I can post or send you. If its GM or other look online to check the right terminal as Black Horse said on your 4-way, 6-way, or 7way etc... w/ a meter or test light.

Just turn your Hazard Lights on. This is checking both your turn signals and brakes at the same time. If you don't have 12 volts at teh female plug on your tow vehicle. Then get your owners manual. Check the relays in the engine compartment. Then check the relays and or fuses under the dash. If this is the case its most likely a relay under the dash. Find another relays of the same kind. Preferably a extra one not being used and swap them out. This will allow you to troubleshoot the cause of your problem before spending any $$.

If you have voltage at the tow vehicle plug. Then check your grounds as the other guys have stated. If you have voltage. Then 9 out of 10 times its a faulty ground. Make sure the terminals on the plugs are not corroded also.