Trailer towing wiring question

mvannie · Post by **mvannie** » Sat Aug 16, 2003 6:42 am

Hi there.

Just got an 03 ZR5 and am looking to wire for towing. I was looking underneath at the bumper, and there are two wiring ports that have covers on them. This got me curious about whether these are for trailering.

Is there an adapter that I can attach to these?

Thanks in advance for any help.

Marc

Mike H. · Post by **Mike H.** » Sat Aug 16, 2003 6:45 am

I recently saw these, and my question is the same. Is there an off-the-shelf harness to use? Mine came with the factory hitch assembly.

Post by **HenryJ** » Sat Aug 16, 2003 7:09 am

Welcome aboard, mvannie

How did you find us?

Finally! , some interest in trailer wiring

I had a post about the wiring for an electric brake controller , that is still unresolved.

The Factory GM wiring supplied with the GM hitch uses an inline tee very similar to the aftermarket units.

As for the lighting wiring, there are also still unanswered questions.

The Crew Cabs received the wiring of the utility (Blazer) not the pickup. So We do have the wiring for the hatch release and rear wiper controls (I used it for my fuel transfer switch and fog lights, in the dash). I have not confirmed this at the rear, but I believe that is what at least one of those plugs is for. There are a couple plugs that are nothing more than ground junctions.

The electrical center (fuse box) under the hood has provisions for separate trailer wiring, ie. fuses for each. But if I remember correctly the connections and wiring are not provided. If you enjoy wiring they could be added.

The one that I still have not located where the factory brake controller plug would go. If you check the wire loom on the left rear frame, near where the lighting connector is, you will find a light blue wire folded over and taped down. I believe that could be the brake controller wire, but have yet to find where it is under the dash, or at the electrical center. EDIT: The blue wire is for the high mount brake light.

Thanks for reviving the interest, maybe now I'll start checking into that again.

mvannie · Post by **mvannie** » Sat Aug 16, 2003 7:37 am

Thanks for your reply.

I found the site on Google after a search for S10 ZR5 (i think), and then a url from mychevytruck.com.

Glad to have found something. I have a Mazda Protege 5, and have found great community of owners on the net, and so when my wife (yeah that right, she owns the truck) bought the truck, I thought I would look around for a similar group.

Anyway, the info you provided is very interesting. I was probably going to go to WalMart for a harness anyway, but I decided to look under just to be familiar before going out.

WOuld I need an S10 harness or a Blazer harness, or are they the same. For now I just need a flat four connection, but I may try to find a round six, for the future and use an adapter. Any recommendations?

thanks again!

Post by **HenryJ** » Sat Aug 16, 2003 7:50 am

mvannie wrote: I was probably going to go to WalMart for a harness anyway...WOuld I need an S10 harness or a Blazer harness, or are they the same.

As far as I know they are the same for all the S-series.There will be an application chart on the box.

For now I just need a flat four connection, but I may try to find a round six, for the future and use an adapter. Any recommendations?

Look for the combination receptacle. It has a square mounting flange with the round six and a separate flat four beside it. I like mine

I have an adapter also but I always end up searching the Suburban to find it (PITA). You will have to buy the harness "Tee" also.

a2b · Post by **a2b** » Sat Aug 16, 2003 12:28 pm

ya, the day i got mine, i just went to walmart and got it. it plugged right in and it took 30seconds.

welcome to the site!!!!

Dragonmaster · Post by **Dragonmaster** » Sat Aug 16, 2003 9:28 pm

The blue wire is for a high mount stop light on a cap. Our trucks have provisions for the brake controller in a splice pack somewhere which was detailed by Mike (LS1 ZR2) on zr2.com. I haven't searched for the post but I am pretty sure it would be in the restored site as it was queit some time ago.

Post by **HenryJ** » Sun Aug 17, 2003 6:33 am

Dragonmaster wrote:The blue wire is for a high mount stop light on a cap. Our trucks have provisions for the brake controller in a splice pack somewhere which was detailed by Mike (LS1 ZR2) on zr2.com. I haven't searched for the post but I am pretty sure it would be in the restored site as it was queit some time ago.

Keep in mind that the wiring for the Utility and pickups differ in many ways.

Post by **HenryJ** » Fri Nov 19, 2004 3:10 pm

HenryJ wrote:... If you check the wire loom on the left rear frame, near where the lighting connector is, you will find a light blue wire folded over and taped down. I believe that could be the brake controller wire, but have yet to find where it is under the dash, or at the electrical center. ...

Mystery solved and confirmed by eric's install:

Eric H wrote:...There is a blue wire on the rear driver's side by the bumper bracket labeled "HI BRAKE" (or something like that; the lettering was quite weathered). I believe the intended purpose of the wire is for toppers with a brake light up in the rear window. I just hooked my light up to this wire and ran a ground to the frame. Works great!

Thank you

malkavian · Post by **malkavian** » Fri Nov 19, 2004 9:19 pm

when I bought mine it already had the wireing harness on it.

jeff024 · Post by **jeff024** » Mon Nov 22, 2004 1:12 pm

yup mine did also and i dont even have a hitch

Swbari00 · Post by **Swbari00** » Wed Dec 29, 2004 9:34 pm

alright, so for me, im slow, is this it: but a harness at walmart and it plugs right into a plug underneath? no splicing (sp?). if so, plug on the driver or passenger side

2bunik · Post by **2bunik** » Thu Dec 30, 2004 2:48 am

YOU MIGHT WANT TO READ THE ABOVE TO YOURSELF.. SORRY i CAN'T DECIPHER THAT ..sorry caps

Maximous · Post by **Maximous** » Thu Dec 30, 2004 8:30 am

mvannie wrote:Thanks for your reply.

Anyway, the info you provided is very interesting. I was probably going to go to WalMart for a harness anyway, but I decided to look under just to be familiar before going out.

WOuld I need an S10 harness or a Blazer harness, or are they the same. For now I just need a flat four connection, but I may try to find a round six, for the future and use an adapter. Any recommendations?

Wally World has the right one you need, thats what i used, it is very simple to install. driver side rear, on the bottom of the bed, you just un plug the wires there, plug the new one in then plug the old one back in, VERY SIMPLE, also, i believe that Walmart also sells the guick connect 4prong to 6prong, al you do is plug it into the 4wire that you just installed, welcome to the site

Maximous · Post by **Maximous** » Thu Dec 30, 2004 8:34 am

Swbari00 wrote:alright, so for me, im slow, is this it: but a harness at walmart and it plugs right into a plug underneath? no splicing (sp?). if so, plug on the driver or passenger side

sorry didn't read this post, yes this is what you want, it plugs in drivers side rear, if i remember correct it is on the outside(drivers side) of the frame, may be wrong but it is on the drivers side no more than 2 or 3 feet from the bumper, tell us how it goes,

2bunik, replace BUT with BOUGHT, see if that helps any, it took me a second to figure it out also

2bunik · Post by **2bunik** » Thu Dec 30, 2004 6:14 pm

got it ... :

Post by **HenryJ** » Thu Dec 30, 2004 6:27 pm

You can see the plugs in this picture-

The GM adapter uses two plugs to "Y" for the trailer light wiring.