Easy one - 4-wire trailer wiring harness question?

[AJMBLAZER]

I'm doing some clean up work on my trailer and vehicles and would like to install the trailer wiring harness I bought for Big Ugly about 3 months ago.

It's one of those "unplug the factory harness, plug this in, then plug the factory stuff into each side of it" setups. Supposed to just fit into the factory wires of a Civy truck without any splicing or anything permanent.

The connection part looks like four circular tubes arranged in a 2x2 square:

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Now here's my question...anybody know on a 1986 M1008 where this connection would be? I can't seem to find anything obvious and before I start pulling on 21 year old wires I figure I'll ask you guys.
Anybody know if a CUCV pickup's additional wiring would complicate this?

 

[ida34]

It should be on the driver's side going up toward the taillight from the bottom. Mine did not work right. Both my 85 and 84 used an older 83 plug that is round spade type connectors. The one that an 85 should have used was a later style gm square weather pac connector. I hope this helps.

 

[AJMBLAZER]

Huh, you know, I stuck my head up there and didn't see much. I'll have to get in there and look some more tomorrow after work.

Eh, worse comes to worse I take it back to NAPA and swap it for the other one. Figures GM does the usual and used up old parts on the CUCV's.

 

[acetomatoco]

You will probably find all the spades in the connectors are corroded and break off when you open the plug.. Best just to get one of the military trailer connectors and plug it into the trailer recepticle on the back of your rig and put a flat four connector harness into the trailer end of it with the packard connectors... will look better and work better...I use intermediate harnesses like that with all my trailers...just keep em in the trailer toolbox and off you go.... For electric brakes, I just run a single extra wire from the controller back to a segregated brake wire on the trailer...works fine for years.

 

[AJMBLAZER]

Re: RE: Easy one - 4-wire trailer wiring harness question?

It should be on the driver's side going up toward the taillight from the bottom. Mine did not work right. Both my 85 and 84 used an older 83 plug that is round spade type connectors. The one that an 85 should have used was a later style gm square weather pac connector. I hope this helps.

Hey ida, think I'm in the same boat as you.
Think I need to go hit NAPA again.

 

[AJMBLAZER]

RE: Re: RE: Easy one - 4-wire trailer wiring harness questio

So...got the new plug all hooked up...but there's an issue. The lights work correctly on the pickup - flashers, turn signals, running lights, and brake lights and ditto for the trailer when I hook it up to the wife's XL7.
Hook the trailer up to Big Ugly and the running lights work fine on both sides of the trailer as does the flasher/signal and brake light on the driver's side of the trailer. However no flasher/signal or brake light on the passenger side. Nothing changes on the truck with the trailer connected.

I did notice that the male end of that plug in my picture above is missing a..."digit" . It's only got 3 of the little prongs...yet how come my lights work fine on the truck?

 

[Recovry4x4]

RE: Re: RE: Easy one - 4-wire trailer wiring harness questio

Only need 3 wires with the exception of a ground. The standard is brown for running yellow for left signal and green for right. Time to check grounds and get out the test light.

 

[AJMBLAZER]

RE: Re: RE: Easy one - 4-wire trailer wiring harness questio

I'm thinking it's gotta be in the trailer wiring harness...right?
If it was in the truck's wiring harness there'd be issues with the truck's lights? I think...

 

[Recovry4x4]

RE: Re: RE: Easy one - 4-wire trailer wiring harness questio

Just chase a few feet at a time with the test light. Make sure you have good grounds on the truck harness and trailer harness. Did you use one of them Hoppy tap light kits?

 

[AJMBLAZER]

RE: Re: RE: Easy one - 4-wire trailer wiring harness questio

NAPA/Hoppy brand plug in harness. The "plug in" part goes in between the two ends that I posted the picture of. The 4 wire setup goes off of that plug and down to the trailer.

 

[Mike_Pop]

I solvd all of my trailer wiring problems by only buying military trailers.

I have a bunch for sale, mostly located in Nevada. Email if you need something.

Mike Pop

 

[AJMBLAZER]

Military trailers are hard to tow behind a 2002 Suzuki XL7. Kinda heavy for my needs. Thanks though.

 

[Mike_Pop]

An M416 would tow nice behind a Suzuki.

Mike

 

[Michael]

Is that wire splice next to the upper plug in your picture stock or a repair to your wiring harness? It could be that the prong broke off and it was repaired with a crimp on wire splice. If your trailer works on the civi truck, I doubt that there is a problem with it. You could look at the wiring diagram in the TM to see if the forth prong is a ground in the plug.

 

[Michael]

Looking at the circuit diagram appendix F of the -20, that plug should have 4 wires. Left, right, tail and back up lights. It looks like the tab broke and someone cut the wires from the plug and spliced them together with a crimp on terminal.

 

[AJMBLAZER]

Thanks man, I'll have to take a look at that later.

 

[JohnFire]

Those plugs on mine goto the tail lights themselves and 3 wires per plug, per side. for the trailer you have running lights, left turn right turn and brake. Brake and the turn signals are the same wires just one per side, hot wire for the running lights, and one wire for ground (ground is from the frame) on a standard trailer wiring harness. Test at the plug and work back in the truck wiring as long as it work with the other vehicle. Also I got rid of all of the military/factory splicing connections and soldered and shrink tubed the connections. Had a similar issue and it was the plug connector for the trailer on the truck. I have eliminated that by going to a 7 blade on the truck. Allows me to add a trailer brake later and has the most adapters for other trailer connections. Good Hunting!

oh and the civy gm/chevy 4pin plug t connector doesn't match(my experience only) , better off wiring yourself. remember the extra wires are blackout light wires for the military trailer connections

 

[notsosanestan]

i got this t connector also for a 83 and only my left side works. i hooked it up on the driverside. i find it hard to believe you need to fun a jumper wire to make it work because why else would they sell it if it did not work? anyone have the correct way to fix it?

 

[dstang97]

because it is for a civi truck. You need to tap off you left side turn signal and cut that wire for the right side and splice it into the main harness. Everyone says to buy this fitting even though it is the wrong part. Even after I tell them it will not work correctly.

 

[hilber]

DId you get if figured out yet