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oem trailer wiring -- where does it go?? [message #300948]

Sat, 21 May 2016 21:41

Messages: 1262
Registered: September 2009

Karma: 0

Senior Member

I'm trying to sort out the stock trailer wiring on our coach.
Specifically, where does it go? I've got the plug at the rear of the
coach which more or less works, but the wires disappear up into the body.
Where is the other end?

Do they run up into the dash somewhere, or just to the tail lights, or ??
The red wire on ours is dead, and I'd like to use the blue wire, but
I've no idea where to find them.

clues would be much appreciated.

thanks,

Karen
1975 26'

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Re: oem trailer wiring -- where does it go?? [message #300952 is a reply to message #300948]

Sat, 21 May 2016 22:44

Adrien G.

Messages: 474
Registered: May 2008
Location: Burns Flat, OK 73624

Karma: 1

Senior Member

Karen,

On my coach the trailer wiring come from inside the left corner of the coach.
There's a connector that connects between the tail light harness (from the dash)
and the rear tail light wiring to power the trailer.

Not knowing your particular (upfiter) model, I still think it's the same.

Adrien & Jenny Genesoto 75 Glenbrook (26-3) Mods LS3.70 FD / Reaction Sys / 80mm Front&Intermidiate / Hydroboost / 16" Tires / Frame Rebuild / Interior Rebuild Yuba City,Ca. Text 530-nine-3-three-3-nine-nine-6

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Re: [GMCnet] oem trailer wiring -- where does it go?? [message #300953 is a reply to message #300952]

Sat, 21 May 2016 22:51

Ken Henderson

Messages: 8726
Registered: March 2004
Location: Americus, GA

Karma: 9

Senior Member

Karen,

Check above the kick panel (above the parking brake handle) for the forward
connector. Kinda hard to find or use with the side panel installed, tho'.

Ken H.

On Sat, May 21, 2016 at 11:44 PM, Adrien Genesoto wrote:

> Karen,
>
> On my coach the trailer wiring come from inside the left corner of the
> coach.
> There's a connector that connects between the tail light harness (from the
> dash)
> and the rear tail light wiring to power the trailer.
>
> Not knowing your particular (upfiter) model, I still think it's the same.
>
>
>
> --
> ”When we avoid the mistakes we might have made, we sometimes make the
> mistakes that we might have avoided.”
>
>
>
> Adrien & Jenny Genesoto
> 75 Glenbrook 26-3
> Yuba City,Ca. 530-nine-3-three-3-nine-nine-6
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach

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Re: [GMCnet] oem trailer wiring -- where does it go?? [message #300960 is a reply to message #300953]

Sun, 22 May 2016 11:13

Messages: 1262
Registered: September 2009

Karma: 0

Senior Member

thanks, I'll do some digging to see what I can find. I'd kind
of expect the 4 trailer wires (yellow, green, brown, white) to go
to the rear tail light, and (hopefully) the blue and red to
somewhere in the dash for a trailer controller. But, who knows.
This is a stock GM model (75 eleganza).

thanks,
Karen

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Re: [GMCnet] oem trailer wiring -- where does it go?? [message #300969 is a reply to message #300960]

Sun, 22 May 2016 12:00

emerystora

Messages: 4442
Registered: January 2004

Karma: 13

Senior Member

The trailer wires go to a six terminal connector in the left rear of the motorhome.
The Yellow wire is for the LH Stop & Directional
The Dark Green wire is for the RH Stop and Directional
The Brown wire is for the tail and marker lights
The White wire is for the trailer ground
The Light Blue wire is a spare wire.

I am not aware of any red wire. If you have one it may have been added by a prior owner.

The spare wire terminates in a connector which is behind the side panel above the driver’s left knee.

The color of the wires in the bundle going to the six way connector are the same color except for the ground wire.
In the bundle it is black. So the white trailer wire connects to the black ground wire.

If you are wiring for a toad where you are using a braking system such as a Brake Buddy you will be using some of your toad battery power. At the end of a days drive you might find your battery in the toad dead. This happened to me so I changed to a seven wire plug from the toad to the motorhome and added another wire connected to the house battery.
I realize that this puts the 12 volt toad battery in parallel with the 12 volt house battery but when you unhook the toad plug you no longer draw any power from the house battery.
I have found that even leaving it connected when parked for the night there are no bad effects. I have been doing it this way for years now. When your GMC engine is running it charges the batteries from the engine’s alternator or if your GMC is plugged into a land line the converter (charger) charges the batteries.

Emery Stora
77 Kingsley
Frederick, CO

> On May 22, 2016, at 10:13 AM, KB wrote:
>
> thanks, I'll do some digging to see what I can find. I'd kind
> of expect the 4 trailer wires (yellow, green, brown, white) to go
> to the rear tail light, and (hopefully) the blue and red to
> somewhere in the dash for a trailer controller. But, who knows.
> This is a stock GM model (75 eleganza).
>
> thanks,
> Karen
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

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Re: [GMCnet] oem trailer wiring -- where does it go?? [message #300982 is a reply to message #300969]

Sun, 22 May 2016 15:52

Messages: 1262
Registered: September 2009

Karma: 0

Senior Member

Thanks Emery, you nailed it.

I can't find any way to get at the forward end of the blue wire without
the difficult removal of the side panel, so I'll just run an extra wire
under the coach. What on earth were they thinking burying it in such
an inaccessible spot!?

The red wire is indeed a PO thing. It was wrapped up in the bundle like it
was stock, but I noticed a small bulge under the wrapping -- they had simply
vampire-tapped a short piece of red wire into the blue wire. Why? Who knows...

thanks everyone for the help.

Karen
1975 26'

emerystora wrote on Sun, 22 May 2016 10:00

The trailer wires go to a six terminal connector in the left rear of the motorhome.
The Yellow wire is for the LH Stop & Directional
The Dark Green wire is for the RH Stop and Directional
The Brown wire is for the tail and marker lights
The White wire is for the trailer ground
The Light Blue wire is a spare wire.

I am not aware of any red wire. If you have one it may have been added by a prior owner.

The spare wire terminates in a connector which is behind the side panel above the driver's left knee.

The color of the wires in the bundle going to the six way connector are the same color except for the ground wire.
In the bundle it is black. So the white trailer wire connects to the black ground wire.

If you are wiring for a toad where you are using a braking system such as a Brake Buddy you will be using some of your toad battery power. At the end of a days drive you might find your battery in the toad dead. This happened to me so I changed to a seven wire plug from the toad to the motorhome and added another wire connected to the house battery.
I realize that this puts the 12 volt toad battery in parallel with the 12 volt house battery but when you unhook the toad plug you no longer draw any power from the house battery.
I have found that even leaving it connected when parked for the night there are no bad effects. I have been doing it this way for years now. When your GMC engine is running it charges the batteries from the engine's alternator or if your GMC is plugged into a land line the converter (charger) charges the batteries.

Emery Stora
77 Kingsley
Frederick, CO

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Re: [GMCnet] oem trailer wiring -- where does it go?? [message #300985 is a reply to message #300982]

Sun, 22 May 2016 16:01

emerystora

Messages: 4442
Registered: January 2004

Karma: 13

Senior Member

Try reaching your hand under the dash and back into the top of the
Side panel. If there is some slack in the wire you might be able to pull it forward and down so as to get to the connector.

Emery Stora

> On May 22, 2016, at 2:52 PM, KB wrote:
>
> Thanks Emery, you nailed it.
>
> I can't find any way to get at the forward end of the blue wire without
> the difficult removal of the side panel, so I'll just run an extra wire
> under the coach. What on earth were they thinking burying it in such
> an inaccessible spot!?
>
> The red wire is indeed a PO thing. It was wrapped up in the bundle like it
> was stock, but I noticed a small bulge under the wrapping -- they had simply
> vampire-tapped a short piece of red wire into the blue wire. Why? Who knows...
>
> thanks everyone for the help.
>
> Karen
> 1975 26'
>
>
> emerystora wrote on Sun, 22 May 2016 10:00
>> The trailer wires go to a six terminal connector in the left rear of the motorhome.
>> The Yellow wire is for the LH Stop & Directional
>> The Dark Green wire is for the RH Stop and Directional
>> The Brown wire is for the tail and marker lights
>> The White wire is for the trailer ground
>> The Light Blue wire is a spare wire.
>>
>> I am not aware of any red wire. If you have one it may have been added by a prior owner.
>>
>> The spare wire terminates in a connector which is behind the side panel above the driver's left knee.
>>
>> The color of the wires in the bundle going to the six way connector are the same color except for the ground wire.
>> In the bundle it is black. So the white trailer wire connects to the black ground wire.
>>
>> If you are wiring for a toad where you are using a braking system such as a Brake Buddy you will be using some of your toad battery power. At the
>> end of a days drive you might find your battery in the toad dead. This happened to me so I changed to a seven wire plug from the toad to the
>> motorhome and added another wire connected to the house battery.
>> I realize that this puts the 12 volt toad battery in parallel with the 12 volt house battery but when you unhook the toad plug you no longer draw
>> any power from the house battery.
>> I have found that even leaving it connected when parked for the night there are no bad effects. I have been doing it this way for years now. When
>> your GMC engine is running it charges the batteries from the engine's alternator or if your GMC is plugged into a land line the converter (charger)
>> charges the batteries.
>>
>> Emery Stora
>> 77 Kingsley
>> Frederick, CO
>
>
>
> _______________________________________________
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Re: [GMCnet] oem trailer wiring -- where does it go?? [message #300991 is a reply to message #300985]

Sun, 22 May 2016 17:01

Messages: 1262
Registered: September 2009

Karma: 0

Senior Member

I was able to pull out a pretty large (10 wire or so) connector from there, but
there's no blue wire to be found. I give up, and will just run another wire.

thanks,
Karen
1975 26'

emerystora wrote on Sun, 22 May 2016 14:01

Try reaching your hand under the dash and back into the top of the
Side panel. If there is some slack in the wire you might be able to pull it forward and down so as to get to the connector.

Emery Stora

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Re: [GMCnet] oem trailer wiring -- where does it go?? [message #300996 is a reply to message #300991]

Sun, 22 May 2016 21:10

Carl S.

Messages: 4186
Registered: January 2009
Location: Tucson, AZ.

Karma: 13

Senior Member

KB wrote on Sun, 22 May 2016 15:01

I was able to pull out a pretty large (10 wire or so) connector from there, but
there's no blue wire to be found. I give up, and will just run another wire.

thanks,
Karen
1975 26'

emerystora wrote on Sun, 22 May 2016 14:01
Try reaching your hand under the dash and back into the top of the
Side panel. If there is some slack in the wire you might be able to pull it forward and down so as to get to the connector.

Emery Stora

Karen, I ran into the same problem when I was wiring in a trailer brake controller. Couldn't find the blue wire in the front at the time, although I saw it later when I was doing some speaker work in the front side panels later on. I just ran a new blue wire to the back, under the coach. I tied it to the fuel tube, etc to get it to stay in place. It has been that way for almost eight years without

Carl Stouffer '75 ex Palm Beach Tucson, AZ. Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles, Solar battery charging. GMCSJ and GMCMI member

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