Home » Public Forums » GMCnet » Blue Extra Wire
| Blue Extra Wire [message #196123] |
Mon, 21 January 2013 17:41  |
midlf
Messages: 2212
Registered: July 2007
Location: SE Wisc. (Palmyra)
Karma: 1
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Senior Member |
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On several occasions it has been mentioned here that the blue extra wire, from the trailer RPO option through the side body harness to the front of the coach, is unable to be located under the dash. Out of curiosity I went looking for it. It is difficult to find because, on my '74, it is not there!
The the photos here:
http://www.gmcmhphotos.com/photos/g6278-blue-wire.html
Unless you have that particular disconnect connector in stock the easiest way to access this blue wire would be to cut it off at the connector and crimp on a common quick disconnect.
I don't know where the blue spare wire is in the rear as I have not yet looked for it.
Steve Southworth
1974 Glacier TZE064V100150 (for workin on)
1975 Transmode TZE365V100394 (parts & spares)
Palmyra WI
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| Re: Blue Extra Wire [message #196227 is a reply to message #196123] |
Tue, 22 January 2013 14:06  |
Wander Inn
Messages: 100
Registered: January 2010
Location: Phoenix Az.
Karma: 0
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Senior Member |
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Steve;
Thanks for the info, I was just looking
for the blue wire.
At the drivers side tail lite, under the
seat, their is a bundle of five wires for the
trailer wireing. BLUE, white, yellow, green
and brown.
Mike
Mike & Chris Hughes
1977 Kingsley
Phoenix, Az.
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| Re: Blue Extra Wire [message #197075 is a reply to message #196123] |
Fri, 01 February 2013 12:41 |
Ray E
Messages: 13
Registered: January 2006
Location: Wauwatosa, Wisconsin
Karma: 0
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Junior Member |
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I've owned GM station wagons and I've pulled a travel trailer. Usually the blue wire with the trailering package option is for running a CHARGING LINE back for charging the travel trailer battery.
Ray Erspamer - 78 Royale
Wauwatosa, Wisconsin 53226
78gmc-roayale@att.net
414-484-9431
Our Web Page: http://ray-lisa.page.tl
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| Re: Blue Extra Wire [message #197282 is a reply to message #196123] |
Mon, 04 February 2013 02:13 |
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John Heslinga
Messages: 632
Registered: February 2011
Location: Edmonton, Alberta, Canada
Karma: 4
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Senior Member |
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Mike and Ray:
Hi Mike: No That wire is not accessible from the Tail light. It is only accessible from inside the coach.
regarding: That Blue wire isn't accessible from the outside behind the light is it??
Thanks Mike
Hi Everyone:
That wire is only a 14ga wire if I recall. With a length of 26 feet and then the length from the connector through a trailer connection system to a trailer battery, I would be afraid that the voltage drop would be high enough that the system probably would not charge a trailer battery appropriately. It might be OK for much shorter Station Wagons. The Light Blue Colour and size actually suggests that the design criteria was that it be used for Electric Brakes. (A controller is placed under the dash and wired into the spare wire) (Blue is a standard colour for electric brakes in the RV world) Almost all vehicles that have trailer wiring options (for many years now) include the wire as well (in most cases they also supply the plug-in and pigtail with 12V power, and brake light connections, so the controller is an easy install. Of course it is only a spare wire in our coach harness from the front of the coach to the back, therefore any user can use it for whatever they want. I've suggested the wire be used for owners that want to install a "High Mount Brake Light". It could also be used as the ignition signal for an Isolation Relay for the trailer battery charging system.(see next)
Modern Factory Trailer Wiring Packages, are much more complex than they were in the past, however. When I serviced Fords, They all had a very heavy wire (8Ga) go from the Battery through a fusible link to the rear of the vehicle. They then used relays and 12 Gauge lighting wires, (10ga to Battery and Ground) to the trailer. (The electric brake wire was 12 Gauge from front to back) The 12 volt Charging relay was controlled by ignition to ensure that the trailer Battery was isolated from the car when the engine was not running. (Later vehicles used a module that sensed when the trailer was plugged in and only enable the relays in this condition)
For quite some time, I've emulated this setup for any trailer wiring install I have done. The trailer lights have always been brighter and quicker to light when I do this, and I have had some very happy customers. It protects the signal light system in the car as well. Stock wiring is far too small to properly light a trailer (especially a RV with a pile of clearance lights.) (I hate following trailers and seeing dim tail and dim / slow to light signal lights that are obviously lit with 10 volts or less) (with modern ECU monitored lighting systems this is, really, the only way to avoid problems and ECU “malfunction indicator lights”) In my coach, I actually supplied the trailer Battery Charging circuit from the house battery (At the rear of the coach. The Charging wire from the front of the coach to the house battery is 2ga and I pretty well get 14volts when the vehicle is running (everything isolates when the ignition is off) While I used a Fuse / Relay Panel I removed from a Ford Winstar, most of my installs simply bundle relays together, and wire the bundle. I wanted to make this install more flexible.
Here are some pictures that may make thins more clear.
http://www.gmcmhphotos.com/photos/discussion-photos/p47279-trailer-relay-panel.html
http://www.gmcmhphotos.com/photos/discussion-photos/p47276-rewired-relay-panel.html
Best Regards
John and Cathie Heslinga
1974 Canyonlands 260
455, Manny tranny and 1 ton, 3:70 LS,
Red Seal Journeyman, DTE, BEd. MEd.
Edmonton, Alberta
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| Re: Blue Extra Wire [message #197300 is a reply to message #196123] |
Mon, 04 February 2013 09:18 |
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John Heslinga
Messages: 632
Registered: February 2011
Location: Edmonton, Alberta, Canada
Karma: 4
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Senior Member |
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Hi Ken:
Re: 3:13 AM !!! Worser'n me! (Probably accounts for thins being more clear.)
Roaming through your album, I saw the electric fan clutch photos. Have you
done anything with those for the GMC?
Being a four finger keyboarder and a fat fingered iPhone pecker means a lot of typos, and being in front of the computer at stupid hours makes me blind to them. But it sure is fun anyway!!
Those fan clutch pictures I uploaded as part of a discussion on the net some time ago to indicate that they were available and used in some of today's longitudinal mounted engine applications where the ECU controls the fan. (An electric controlled clutch is cheaper than adding a fan motor) Many transport truck applications use electric ECU controlled clutches now too. I have not had any issues with my factory clutch, so have not needed to try using one of these. I highly suspect that there will be none that are available that could be used as "bolt in", and can imagine the adaptive machining that would need to be done.
Best regards
John and Cathie Heslinga
1974 Canyonlands 260
455, Manny tranny and 1 ton, 3:70 LS,
Red Seal Journeyman, DTE, BEd. MEd.
Edmonton, Alberta
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| Re: [GMCnet] Blue Extra Wire [message #197318 is a reply to message #197300] |
Mon, 04 February 2013 10:36 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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From your photos, it would appear that adapters for the mounting
surfaceswould be pretty
straigh-forward. The biggest problem would probably be providing a
mounting for the wiring "boom" clear of the fan blades. I'm not about to
tackle it, but if I had clutch problems, I'd be tempted.
Thanks,
Ken H.
On Mon, Feb 4, 2013 at 10:18 AM, John Heslinga wrote:
>
>
> Hi Ken:
>
> Re: 3:13 AM !!! Worser'n me! (Probably accounts for thins being more
> clear.)
> :)
>
> Roaming through your album, I saw the electric fan clutch photos. Have you
> done anything with those for the GMC?
>
>
>
> Being a four finger keyboarder and a fat fingered iPhone pecker means a
> lot of typos, and being in front of the computer at stupid hours makes me
> blind to them. But it sure is fun anyway!!
>
> Those fan clutch pictures I uploaded as part of a discussion on the net
> some time ago to indicate that they were available and used in some of
> today's longitudinal mounted engine applications where the ECU controls the
> fan. (An electric controlled clutch is cheaper than adding a fan motor)
> Many transport truck applications use electric ECU controlled clutches now
> too. I have not had any issues with my factory clutch, so have not needed
> to try using one of these. I highly suspect that there will be none that
> are available that could be used as "bolt in", and can imagine the adaptive
> machining that would need to be done.
>
>
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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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