Cascade Crew

91RSVert · Posted: Wed Jun 20, 2012 6:14 pm Post subject: trailer/truck light problem

ok, so when ever we hook my car hauler up to my 1ton, it dims the lights on the truck? When ever we hook it to my friends 3/4ton, the trailer has no taillights, but has brake/turn? What is going on?

Details:
20ft hauler
Full LED lights, tails, 4 side marker, 4 lp lights, tripple clearance bar.
7pin plug
4 tire brakes
constant power pin is wired to a battery for the removeable winch.

1997 chevy 1ton
7pin plug is added on(not factory)
brand new super fancy bj model brake controller.
power pin is ran to fuse box under hood with 30amp fuse.

2005 dodge 3/4ton
7pin plug is factory installed.
basic run of mill brake controller.
no wire connected for battery/winch combo.

chevymad · Posted: Wed Jun 20, 2012 6:47 pm Post subject:

There are at least 3 different correct versions of the 7 pin connector. Newer cars like your buds usually have a different pattern then everyone used to use. All 3 use the same plug in.

91RSVert · Posted: Thu Jun 21, 2012 2:46 am Post subject:

It worked before. This just started a few weeks ago. So i would suspect we have the correct version on all 3.

chevymad · Posted: Thu Jun 21, 2012 6:22 am Post subject:

Then its time to take things apart and take a look.

QwkTrip · Posted: Thu Jun 21, 2012 7:39 pm Post subject:

There aren't many wires on a trailer. Just start checking circuits one at a time for problems. Check the pinouts on the trailer connector and make sure the pinouts on trucks are same.

aaron_sK · Posted: Thu Jun 21, 2012 7:50 pm Post subject:

91RSVert · Posted: Fri Jun 22, 2012 4:28 am Post subject:

The wires where the lights hook up are soldered. The only ones that should come loose are up in the plug. Friend claims he took that apart to check it and all are tight.

Guess its time to start unsoldering each light?

aaron_sK · Posted: Fri Jun 22, 2012 6:27 am Post subject:

Or you could just check the resistance... if there is a multimeter anywhere in the state of Arkansas. Razz

91RSVert · Posted: Fri Jun 22, 2012 12:16 pm Post subject:

Ive got about 4 in my house. Laughing

But being their all connected. How do I check 1 light to see which one is the trouble spot?

QwkTrip · Posted: Sat Jun 23, 2012 8:24 am Post subject:

You said the truck headlights are dimming down when you hook up the trailer? That's a tell-tale sign that system voltage is being pulled down by a high current draw. Could be an electrical short to ground somewhere on the trailer.

I've never done anything with trailer wiring but this is how I might break down the problem.

- Make sure the trailer connector has the correct pin locations for the wiring of receptacle on your truck. Just because it appeared things worked earlier doesn't mean everything worked properly. There's just no sense in troubleshooting the whole trailer wiring without knowing for sure that the pinouts are correct.

- Remove all the light bulbs from trailer and check for resistance between the B+ lighting leads in the 7-pin plug and a bare metal spot on the trailer frame. If you get conductivity then there is a short to ground somewhere in your lighting wiring on the B+ side. (Don't test the ground wire for a short to ground.... Laughing

) You can isolate a short with a clamp-on ammeter by measuring current draw to each leg of wiring. The leg with high current draw is the leg with a short circuit. At that point you just need to use your eyes and hands to find an area with damaged wire and fix it.

Check the health of battery inside the emergency break-away box. If that battery has shorted cells then it can pull a lot of current off the charge circuit. Replace battery if necessary. Make sure the emergency pull cord is in the "ready" position and hasn't been pulled.

If that doesn't yield anything then all that's left is the electric brakes.

An alternative to quickly finding which circuit is the problem is to use the clamp-on ammeter on the truck side of wiring near the connector. The wire with excessively high current is the same circuit on trailer with the electrical short. This only works if you're willing to put power to everything again and fuses aren't blowing or wires melting on the truck side.

aaron_sK · Posted: Sat Jun 23, 2012 8:33 am Post subject:

chevymad · Posted: Sat Jun 23, 2012 8:56 am Post subject:

Trailer works differently on 2 different trucks. Therefore there is a wiring problem on one of the trucks.

Find the draw issue as previously explained.

QwkTrip · Posted: Sat Jun 23, 2012 10:48 am Post subject:

It's not a competition, Aaron. Quit trying to make it one. You're a smart guy and repairing cars is one of your talents. You don't see my talents because those subjects are never a topic of discussion at this site.

Using a spare battery is a good idea. But you'll blow the fuse on the multimeter if you try to measure shorted current.

chevymad · Posted: Sat Jun 23, 2012 10:58 am Post subject:

Test light works great for finding a short. Remove all the bulbs on the circuit and hook the test light between the positive of the battery and the circuit to be tested. If its shorted the test light will light. Simply disconnect at any splice or cut wire until the short is found.

QwkTrip · Posted: Sat Jun 23, 2012 11:02 am Post subject:

Have you ever tried those tools that you just pass by the wire to detect location of shorts? Curious if they really work worth beans?

aaron_sK · Posted: Sat Jun 23, 2012 11:10 am Post subject:

QwkTrip · Posted: Sat Jun 23, 2012 11:31 am Post subject:

I don't know what the tool is called. I just remember seeing something in a catalog a long time ago that looked like a wand that is passed close to the wire loom and gives off an audible signal when it passes over a shorted area of wire. Just curious if anybody has ever used one and if it's worth a darn or just hype?

aaron_sK · Posted: Sat Jun 23, 2012 11:32 am Post subject:

Ahh... I see now you edited to clarify your post. I have seen what you are describing before, but have never used one personally.

QwkTrip · Posted: Sat Jun 23, 2012 11:36 am Post subject:

I can type 200 words per minute by I have to backspace over 190 of those words.

aaron_sK · Posted: Sat Jun 23, 2012 11:38 am Post subject:

Nice. I seem to often have the same problem. In fact I did it twice just typing this alone.