Home » Public Forums » GMCnet » Wiring Vacuum Pump (Brake Vacuum)
| Wiring Vacuum Pump [message #108201] |
Sat, 11 December 2010 12:40  |
George Beckman
Messages: 1085
Registered: October 2008
Location: Colfax, CA
Karma: 11
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Senior Member |
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I have my JC4 pump installed on one of JimK's mounting brackets and am pleased as can be with the exception that it did not work.
I studied the wiring explanation on Gene's site and hooked the ACC wire into the yellow wire that goes to the heater fan as per instructions.
http://www.gmcmhphotos.com/photos/showphoto.php?photo=4675&cat=3471
No luck. When I tested the yellow wire, I could only get 0.2 volts, which was not enough to trigger the pump relay. I have a '74 coach if that matters. If I hook the Acc wire to 12 volts, the pump runs. (quiet little thing... love it.)
I was wondering of one of the smart guys knows of another handy ACC wire under the "hoods", or do I get to pull the lower dash skirt for the 12,000th time and fish for an ignition controlled wire? I love standing on my head trying to get my varilux lenses to focus on something... anything. It is these moments we GMC fellows live for.
'74 Eleganza, SE, Howell + EBL
Best Wishes,
George
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| Re: Wiring Vacuum Pump [message #108204 is a reply to message #108201] |
Sat, 11 December 2010 12:47  |
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mike miller
Messages: 3576
Registered: February 2004
Location: Hillsboro, Oregon
Karma: 0
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| George Beckman wrote on Sat, 11 December 2010 10:40 |
... I studied the wiring explanation on Gene's site and hooked the ACC wire into the yellow wire that goes to the heater fan as per instructions.
http://www.gmcmhphotos.com/photos/showphoto.php?photo=4675&cat=3471
No luck. When I tested the yellow wire, I could only get 0.2 volts, which was not enough to trigger the pump relay. I have a '74 coach if that matters. ...
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The "1974" DOES matter.
Later coaches did not have an off on the fan so some have "made" an off position by disconnecting the above wire. Gene just figured out how to use the "loose" wire for something useful.
Your coach should have an "off" position on the fan. If you turn on your fan your pump should run... not that I would leave it that way!
Mike Miller -- Hillsboro, OR -- on the Black list
(#2)`78 23' Birchaven Rear Bath -- (#3)`77 23' Birchaven Side Bath
More Sidekicks than GMC's and a late model Malibu called 'Boo'
http://m000035.blogspot.com
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| Re: [GMCnet] Wiring Vacuum Pump [message #108208 is a reply to message #108201] |
Sat, 11 December 2010 13:33 |
emerystora
Messages: 4442
Registered: January 2004
Karma: 13
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Senior Member |
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On Dec 11, 2010, at 11:40 AM, George Beckman wrote:
>
>
> I have my JC4 pump installed on one of JimK's mounting brackets and am pleased as can be with the exception that it did not work.
>
> I studied the wiring explanation on Gene's site and hooked the ACC wire into the yellow wire that goes to the heater fan as per instructions.
>
> http://www.gmcmhphotos.com/photos/showphoto.php?photo=4675&cat=3471
>
> No luck. When I tested the yellow wire, I could only get 0.2 volts, which was not enough to trigger the pump relay. I have a '74 coach if that matters. If I hook the Acc wire to 12 volts, the pump runs. (quiet little thing... love it.)
>
> I was wondering of one of the smart guys knows of another handy ACC wire under the "hoods", or do I get to pull the lower dash skirt for the 12,000th time and fish for an ignition controlled wire? I love standing on my head trying to get my varilux lenses to focus on something... anything. It is these moments we GMC fellows live for.
> --
> '74 Eleganza, SE, Howell + EBL
> Best Wishes,
> George
No need to go under the lower dash. Just run a wire over to the "stud" that is near your battery isolator on the aluminum panel just under the passenger window. Put an in line fuse in the wire
Emery Stora
77 Kingsley
Santa Fe, NM
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| Re: [GMCnet] Wiring Vacuum Pump [message #108212 is a reply to message #108201] |
Sat, 11 December 2010 15:06 |
jayrabe
Messages: 509
Registered: June 2009
Location: Portland, OR
Karma: 0
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Here's what I did, an idea I got from DJ Eberhard here in Oregon. Added two aux fuse panels in engine compartment where the nearly useless compartment light was located, one of them powered from the battery, and the other from the ignition. Haven't yet hooked up the vacuum pump, but since it requires both always-hot and hot-with-ignition, these fuse blocks will give me both. Plus, they use easy to replace ATC fuses, eliminating the inline fuses completely. Lots more convenient and tidy.
http://www.gmcmhphotos.com/photos/showphoto.php?photo=37188&title=aux-fuse-blocks&cat=5676
Got the ignition power from the chassis fuse block in the glove compartment. White wire in picture. Previously there was a wire powering my Howell EFI connected there, so I routed the EFI to my new fuse block and powered the ignition fuse block from the lug instead.
http://www.gmcmhphotos.com/photos/showphoto.php?photo=37189&title=chassis-fuse-block&cat=5676
I do have a question, though. The little fuse on the end of the chassis block that supposedly runs "instrument lamps" does not seem to have power on either end whether engine is off or running. Any clues?
http://www.gmcmhphotos.com/photos/showphoto.php?photo=37190&title=chassis-fuse-blockannotated&cat=5676
JWID
J
76 PB
Portland, OR
> From: gbeckman@pggp.com
> I have my JC4 pump installed on one of JimK's mounting brackets and am pleased as can be with the exception that it did not work.
> I studied the wiring explanation on Gene's site and hooked the ACC wire into the yellow wire that goes to the heater fan as per instructions...
...
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| Re: [GMCnet] Wiring Vacuum Pump [message #108216 is a reply to message #108212] |
Sat, 11 December 2010 15:53 |
emerystora
Messages: 4442
Registered: January 2004
Karma: 13
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Senior Member |
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On Dec 11, 2010, at 2:06 PM, Jay Rabe wrote:
>
> Here's what I did, an idea I got from DJ Eberhard here in Oregon. Added two aux fuse panels in engine compartment where the nearly useless compartment light was located, one of them powered from the battery, and the other from the ignition. Haven't yet hooked up the vacuum pump, but since it requires both always-hot and hot-with-ignition, these fuse blocks will give me both. Plus, they use easy to replace ATC fuses, eliminating the inline fuses completely. Lots more convenient and tidy.
> http://www.gmcmhphotos.com/photos/showphoto.php?photo=37188&title=aux-fuse-blocks&cat=5676
>
> Got the ignition power from the chassis fuse block in the glove compartment. White wire in picture. Previously there was a wire powering my Howell EFI connected there, so I routed the EFI to my new fuse block and powered the ignition fuse block from the lug instead.
> http://www.gmcmhphotos.com/photos/showphoto.php?photo=37189&title=chassis-fuse-block&cat=5676
>
> I do have a question, though. The little fuse on the end of the chassis block that supposedly runs "instrument lamps" does not seem to have power on either end whether engine is off or running. Any clues?
> http://www.gmcmhphotos.com/photos/showphoto.php?photo=37190&title=chassis-fuse-blockannotated&cat=5676
>
That little 4 amp fuse for the instrument lamps receives its power only when the headlight switch is on the park position of the headlight position. If you look at the wiring diagram for your GMC you will see the fuse shown in the area under "lighting" by the headlight switch in the diagram.
If you turn on your headlights and check the fuse you will find that it now has power.
Emery Stora
77 Kingsley
Santa Fe, NM
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| Re: [GMCnet] Wiring Vacuum Pump [message #108217 is a reply to message #108212] |
Sat, 11 December 2010 16:27 |
Mr ERFisher
Messages: 7117
Registered: August 2005
Karma: 2
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Senior Member |
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I only use breakers for terminal strips, don't like hidden fuses.
http://www.gmcmhphotos.com/photos/showphoto.php?photo=35548&title=power-distribution-using-circuit-breakers&cat=5581
http://goo.gl/QRRZM
don't want the pump to stop because someone blew a fuse ;>)
glad you got-er-done
gene
On Sat, Dec 11, 2010 at 1:06 PM, Jay Rabe <jayrabe@hotmail.com> wrote:
>
> Here's what I did, an idea I got from DJ Eberhard here in Oregon. Added two
> aux fuse panels in engine compartment where the nearly useless compartment
> light was located, one of them powered from the battery, and the other from
> the ignition. Haven't yet hooked up the vacuum pump, but since it requires
> both always-hot and hot-with-ignition, these fuse blocks will give me both.
> Plus, they use easy to replace ATC fuses, eliminating the inline fuses
> completely. Lots more convenient and tidy.
>
> http://www.gmcmhphotos.com/photos/showphoto.php?photo=37188&title=aux-fuse-blocks&cat=5676
>
> Got the ignition power from the chassis fuse block in the glove
> compartment. White wire in picture. Previously there was a wire powering my
> Howell EFI connected there, so I routed the EFI to my new fuse block and
> powered the ignition fuse block from the lug instead.
>
> http://www.gmcmhphotos.com/photos/showphoto.php?photo=37189&title=chassis-fuse-block&cat=5676
>
> I do have a question, though. The little fuse on the end of the chassis
> block that supposedly runs "instrument lamps" does not seem to have power on
> either end whether engine is off or running. Any clues?
>
> http://www.gmcmhphotos.com/photos/showphoto.php?photo=37190&title=chassis-fuse-blockannotated&cat=5676
>
> JWID
>
> J
> 76 PB
> Portland, OR
>
>
> > From: gbeckman@pggp.com
> > I have my JC4 pump installed on one of JimK's mounting brackets and am
> pleased as can be with the exception that it did not work.
> > I studied the wiring explanation on Gene's site and hooked the ACC wire
> into the yellow wire that goes to the heater fan as per instructions...
> ...
>
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
--
Gene Fisher -- 74-23,77PB/ore/ca
“Give a man a fish; you have fed him for today --- give him a URL and
-------
http://gmcmotorhome.info/
Alternator Protection Cable
http://gmcmotorhome.info/APC.html
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| Re: [GMCnet] Wiring Vacuum Pump [message #108220 is a reply to message #108216] |
Sat, 11 December 2010 16:50 |
jayrabe
Messages: 509
Registered: June 2009
Location: Portland, OR
Karma: 0
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Senior Member |
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Allright! That makes sense. Thanks Emory.
So many tricks to learn on these old babies. :-)
J
76 PB
Portland, Or
> From: emerystora@mac.com
> That little 4 amp fuse for the instrument lamps receives its power only when the headlight switch is on the park position of the headlight position. If you look at the wiring diagram for your GMC you will see the fuse shown in the area under "lighting" by the headlight switch in the diagram.
>
> If you turn on your headlights and check the fuse you will find that it now has power.
>
> Emery Stora
> 77 Kingsley
> Santa Fe, NM
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