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Discussion Starter #1
Trying to figure out the easiest way to install 7 pin trailer hook up for my burb with the factory towing. I already have the hopkins plug and play attachment for a 4 flat trailer, but about to buy a travel trailer and need to install a brake controller and the whole 7 pin wiring, I have the thick orange and blue wires hanging down from the back, need to check under hood to see if a prior owner has hooked them up?? I found this U tube video and thinking this is what has to happen??
 

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If your truck came from the factory with the tow bar and hitch receiver mounted, the 7 pin connector should be tucked up under something at the rear of your truck, maybe under the spare
The wires for the brake controller should be under the dash
 

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Discussion Starter #3
I will look, but thinking I had the 4 pin prewired as I only had to insert the hopkins part in middle of connector to get a 4 pin flat connector?? The orange and blue "heavy duty" wires are just hanging loose in the rear of truck under the bumber and I know those are the brake controller (blue) and power ( orange) from what I have been reading and as shown on this video. I think the 2 "heavy duty" wires are just run from factory under vehicle and end up unattached just under the master cylinder. So maybe I do not have the factory towing?? There is what looks like a factory tranny cooler mounted in front of radiator, so I was just guessing I have the "factory tow"?? Gowing out now to check things out and see if I can make sense of things. I want to order the parts I need from amazon (out in mountains, no stores) and try and get it figured out so I can have brakes, controller and lights to get the RV Trailer I found next week. Thanks!!
 

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If it gets to wiring confusion, here are some wire diagrams as what colors are to what.

In addition, some truck accessory / travel trailer places can get "in series" 7 pin connectors for particular vehicles that just snap into the existing factory wire harness in case you can't or don't have the 7 pin connector.

Trailer Wiring 7 Pin B.jpg
Trailer Wiring 7 Pin C.jpg
Trailer Wiring 7 Pin.jpg
 

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Discussion Starter #6
any idea what code to look for? thanks for guidance. i got the 4 flat working today and looks like the orange and blue wire might just be ending at the space below master cylinder. So not sure yet on the 7 pin, no sign of any connector tucked away and the loose blu and orange wires make me think I will have to do as the video describes and need the kit they suggest for everything i need except for the grommet after you drill hole through firewall to get to the brake controller.
 

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Discussion Starter #7
Thanks Rick for the 7 pin break down. I have to go to the big city tomorrow and might stop at RV place to see what they say about getting my factory 4 flat to a 7 pin, maybe I can get a bid and advice that way. I would like to do this myself, I like to solder and heat shrink electrical connections as the quick connectors everyone use always fail later from corossion or vibration.
 

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Here's the 7 way harness for your sub. It plugs into the junction at the rear driver's frame rail. Saves time and eliminates wiring problems.

https://www.etrailer.com/Custom-Fit-Vehicle-Wiring/Curt/C55774.html

Spend some time on the site. They have install videos for the harness and brake controller. There is a brake controller pigtail available for your sub that makes for an easy install for the controller.

Ted
 
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Discussion Starter #9
Here's the 7 way harness for your sub. It plugs into the junction at the rear driver's frame rail. Saves time and eliminates wiring problems.

https://www.etrailer.com/Custom-Fit-Vehicle-Wiring/Curt/C55774.html

Spend some time on the site. They have install videos for the harness and brake controller. There is a brake controller pigtail available for your sub that makes for an easy install for the controller.

Ted
Thanks Ted, I have looked at etrailer site and it looks like I am going to have to hard wire the brake controller and splice into a small white wire that is under dash and goes to brake and can be found using a circuit tester to see when it is hot after dressing the brake pedal as described in the video. Looks like I need the etrailer etbc7 kit etrailer sells for $56. I can get the prodogy P3 controller a bit cheaper on amazon than from etrailer, but amazon does not have the Eetbc7 kit which looks like it has every part I will need except for a grommet for going thru the firewall after I drill a hole for the wires and a nut to fit onto the fuse block for fastening a hot lead as described in the video. I see their are 2 types of 7 pin connectors, a 7 blade and 7 round, pretty sure it will be the 7 blade, but I do have the trailer yet. Here is where etrailer web site got my to when I searched for 98 suburban. I appreciate everyones help, I figured I was not first to do this and no need to reinvent the wheel. https://www.etrailer.com/bc-1998_GMC_Suburban.htm
 

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The brake controller pigtail used to be in the glove box on new GMT800 vehicles. Maybe you missed out. Wouldn't hurt to call the dealer to check. It plugs into the underdash electrical center near your left foot and plugs into the P3. I have a P3 they're a very good controller.

Ted
 

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Discussion Starter #11
The brake controller pigtail used to be in the glove box on new GMT800 vehicles. Maybe you missed out. Wouldn't hurt to call the dealer to check. It plugs into the underdash electrical center near your left foot and plugs into the P3. I have a P3 they're a very good controller.

Ted
Yes, I am thinking the GMT 400 does not have the pigtail/harness. I can stop by dealer today while in montrose, co, maybe they can help me figure it out and check the vin# to see about factory tow options.
 

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[QUOTE="mcmars, post: 2819001, member: ] I have to go to the big city tomorrow and might stop at RV place to see what they say about getting my factory 4 flat to a 7 pin,[/QUOTE]

Your 4 pin is not factory, to the best of my knowledge, factory only supplies 7 pin.
 

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Yep on no 4 flat factory connector. I usually use a coiled 4 flat extension adapter that I leave on the trailer. Most of the aftermarket 7 way harnesses that replace the factory harness have the 4 flat built in beside the 7 way. Unpractical to replace the harness just for the 4 flat but desirable if you need the harness.

I've found the most useful adapter is the 12V power outlet with the 5 flat connector. A 4 flat plug right in. You can configure the 5th pin as brake, backup lights or 12V aux. I think it was originally conceived as a surge brake turn off for backing the trailer. If your trailer does have surge brakes you can double down for brake turn off and backup lights.

Ted
 

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Discussion Starter #14
The hopkins 41125 adapter is what I used to get the 4 flat working. It plugged right into the wire harness on back of burb and I only had to drill a hole for the white ground wire. Here is is:https://www.amazon.com/gp/product/B0002Q7BZ4/ref=oh_aui_detailpage_o01_s02?ie=UTF8&psc=1
Looks like I can then plug the 4 flat into this hopkins 7 pin part #47185https://www.amazon.com/Hopkins-Towing-Solutions-47185-Multi-Tow/dp/B0002Q80GS/ref=pd_bxgy_263_img_2?_encoding=UTF8&pd_rd_i=B0002Q80GS&pd_rd_r=3YXH3RJ2BF6CHPENYGEJ&pd_rd_w=XVWU9&pd_rd_wg=lm5GK&psc=1&refRID=3YXH3RJ2BF6CHPENYGEJ . But then will have to hardwire in the blue and orange large gauge wires I have hanging down from the back of vehicle for power and brake controller and then go up front to install the circuit breakers and connect to fuse block and drill thru the firewall to get to the brake controller and hard wire the 4 wires that go to the controller. Maybe there a factory deal in the back and a factory plug in for the controller, but I cannot find them and none of the service folks or RV people I spoke with today knew about an easier way. I will keep looking, seems like this must not be such a mystery to figure out?? I
 

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Discussion Starter #15
OK, I figured it out by going to the tekonsha site and selecting for 1998 GMC K1500 burb and selecting "all products" It shows 7 different adaptors incuding the 4 flat " T" like I got the hopkins version of, but at end of page under "Brake Controller harness" it says, "No plug n play brake control harness available for this vehicle, must be hardwired. To insure you locate proper vehicle wiring for stoplight, contact local authorized deal or vehicle manufacturer". So hardwire it is! Thank go for Utube! http://www.tekonsha.com/fit-guides/electrical-selector
 

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Discussion Starter #16
I found an even better U tube video from etrailer on 1997 chevy c/k PU. This breaks it down even easier. First attach the 7 blade connector bracket to rear bumper/hitch, hardwire the 7 wires into the connector as show and attaching the rear ground to frame. GM has already installed the orange and blue 10 gauge wire from front to back of vehicle, and has included a pair of 30 amp fuses in the fuse box under the hood. All you need to do is attach the orange wire that has a ring onto one of the 2 studs on rear of fuse box next to the (2) 30 amp fuses and then attach ground to side of engine compartment, drill a hole for a grommet to go through firewall and hook up 4 wires to the brake controller unit harness. I guess this was the "plug n play" for the older suburbans, newer vehicles get the plug in harnesses that are vehicle specific and a bit easier. I will add some silicon sealant to the grommet, looks like a mouse hole and cold/hot air infiltration hole, already got a mouse, he ate all my almonds!
 

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I just watched that video. it has a great rundown and all the info to connect a 7 way almost properly.

what I dont like is how he made his connections. when I first hooked mine up I did something similar with electrical tape.

I also didnt like his ground connection, you should clean ground connections to bare metal, apply a little bit of dielectric grease, assemble the connection and then cover in alot of dielectric grease.

so back to the splicing of the wires.... this way will last a few years at best and will no doubt cause a headache eventually. solder and shrink wrap every connection with automotive double walled shrink wrap, its waterproof.

doing these 2 steps will make the wiring last forever. covering the wires and making it all nice with a plastic loom cover or something better like a split propane hose really completes the job. the less electrical tape the better.

I suspect this is how all rv/tow/trailer shops make their connctions, its a form of job security.


Al
 
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Discussion Starter #19
Yes, I found them, I could see mine as I had cleaned engine when I got vehicle and see them on both ends. Your other post is exactly like the video I just posted. Looks very easy to hook up the orange to the fuse panel green 30 amp fuses with the 2 studs, one for orange and other to go to power the brake controller after drilling hole through firewal and a gromet. I ordered everything I needed this am on amazon. BTW Napa wants $282 for the prodigy P3 controller and amazon is $117 today. Napa guy said their wholesale on P3 is $200! What a sad state for future of retail! Thanks for the awesome post, I am surprized more folks have not posted on this issue, maybe our posts will help others??
 

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Discussion Starter #20
I just watched that video. it has a great rundown and all the info to connect a 7 way almost properly.

what I dont like is how he made his connections. when I first hooked mine up I did something similar with electrical tape.

I also didnt like his ground connection, you should clean ground connections to bare metal, apply a little bit of dielectric grease, assemble the connection and then cover in alot of dielectric grease.

so back to the splicing of the wires.... this way will last a few years at best and will no doubt cause a headache eventually. solder and shrink wrap every connection with automotive double walled shrink wrap, its waterproof.

doing these 2 steps will make the wiring last forever. covering the wires and making it all nice with a plastic loom cover or something better like a split propane hose really completes the job. the less electrical tape the better.


I suspect this is how all rv/tow/trailer shops make their connctions, its a form of job security.


Al
Yes I solder and heat shrink and just ordered some 3-1 marine grade heat shrink with adhesive. I always wire brush, scrape to bare metal and use dielectric grease! I lothe those connectors, always fail. I found some ring terminals that were burly and had heat shrink with adhesive for marine use, I guess it is as good as you can do. I also have a heavy duty set of pliers with the notch cut out for crimping instead of the normal cheap all purpose tool that does not work well, not sure how to do ring terminals without a crimp??
 
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