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GMC fuel gauge wiring [message #175887]

Sat, 07 July 2012 13:11

Scooby Doo

Messages: 92
Registered: May 2012
Location: Miami, Florida

Karma: 4

Member

Hello All,

I am currently attempting to put some gauges into my dashboard.
I have decided to put in a mechanical oil pressure and water temperature, and also a fuel gauge to replace the stock cluster.

I have purchased a 0 to 90 ohm fuel gauge and I am very confused about how to connect the wiring to it. The GMC gauge cluster has a plug in wire harness (lots of wires!) to operate all three gauges.
On the fuel gauge I purchased, I have three terminals. One for ground, one for ignition switch, and one for the sending unit.
Will I be dealing with more than one sending wire ? (since I have two gas tanks)
Will I be putting the two wires together if so ?
Or, will I need to have two separate gauges and have to buy a second fuel gauge ?
I am hoping to just have one fuel gauge as I did on my stock GMC set up.
I am also attempting to put up a link to a photo of the stock wiring harness to the GMC gauge cluster.
photo link : GMC gauge cluster

I read the forum every day and have been learning so much from all the random posts. I am learning more & more each day about our GMC motorhome. The GMC.net is full of information.
I look forward to hearing back from some of you tech guys.

Thank you in advance.

Glenn Gardner

Glenn & Elaine Gardner... Miami, Florida... 1976 Royale (transmode) TZE366V100733

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Re: [GMCnet] GMC fuel gauge wiring [message #175890 is a reply to message #175887]

Sat, 07 July 2012 13:58

Ken Henderson

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

Karma: 9

Senior Member

Glenn,

Check the wiring diagram and you'll find that the OEM fuel gauge is fed by
a Gray wire with double black stripes. That wire is in turn fed by either
the Aux or Main tank sender, dependent upon the position of the fuel tank
selector switch. In your photo of the connector, the second wires from the
right, in cavity C, should be that Gray w/dbl black wire.

Connect the new gauge to ignition, ground, and that Gray w/dbl black wire
and you should be good to go -- IF the tank senders are good.

Ken H.

On Sat, Jul 7, 2012 at 2:11 PM, Glenn Gardner wrote:

> ...

I have purchased a 0 to 90 ohm fuel gauge and I am very confused about how
> to connect the wiring to it. The GMC gauge cluster has a plug in wire
> harness (lots of wires!) to operate all three gauges.
> On the fuel gauge I purchased, I have three terminals. One for ground, one
> for ignition switch, and one for the sending unit.
> ...

I am also attempting to put up a link to a photo of the stock wiring
> harness to the GMC gauge cluster.
> photo link : http://www.gmcmhphotos.com/photos/u20658-scooby-doo.html
> ...
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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: GMC fuel gauge wiring [message #175893 is a reply to message #175887]

Sat, 07 July 2012 14:12

Scooby Doo

Messages: 92
Registered: May 2012
Location: Miami, Florida

Karma: 4

Member

Ken H,

Thank you very much for your reply.

The current (stock) gauge worked fine (on Main & Aux.), so I will assume that once I hook up the new one correctly it too should work as the original one did.

Thank you again,
I could not have figured it out without your help. Smile

Sincerely,
Glenn Gardner

Glenn & Elaine Gardner... Miami, Florida... 1976 Royale (transmode) TZE366V100733

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Re: GMC fuel gauge wiring [message #175895 is a reply to message #175893]

Sat, 07 July 2012 14:23

WD0AFQ

Messages: 7111
Registered: November 2004
Location: Dexter, Mo.

Karma: 207

Senior Member

Glen, great to see you here. This is the place, as you have found out, to help you keep your GMC rolling for years to come.
Without this group I would have sold my GMC a long time ago.
Think about coming up to Dothan next March and seeing what fun we have when together in person. There are only a couple of cranky guys that show up. Everyone else is into "fun". Very Happy

Dan

3 In Stainless Exhaust Headers One Ton All Discs/Reaction Arm 355 FD/Quad Bag/Alum Radiator Manny Tran/New eng. Holley EFI/10 Tire Air Monitoring System Solarized Coach/Upgraded Windows Satelite TV/On Demand Hot Water/3Way Refer

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Re: GMC fuel gauge wiring [message #175896 is a reply to message #175887]

Sat, 07 July 2012 14:39

Scooby Doo

Messages: 92
Registered: May 2012
Location: Miami, Florida

Karma: 4

Member

Hello Dan,

Thank you for your comments.
We just got back form our 3rd trip in our GMC.
We still are getting used to it, and love it more with each trip.

I was just trying to get accurate info from my engine and am currently installing quality gauges in our GMC. (A big thanks to Ken H !)

I feel very fortunate to be a member of this GMC community.
I have already learned so much on this forum, and we have joined the Sunshine Statesmen GMC club and have met a handful of their members (all so very nice)

I am hoping that next year, the Mrs. & I feel more comfortable going futher from home.
So far we head in any direction, but only 200 or so miles from home. As we are more comfortable with the reliability of our GMC we shall stray further, and hopefully leave the state of Florida by next year.
Hope to meet you in person one day. Smile

Sincerely,
Glenn Gardner...G2photosmx.com

Glenn & Elaine Gardner... Miami, Florida... 1976 Royale (transmode) TZE366V100733

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Re: [GMCnet] GMC fuel gauge wiring [message #175898 is a reply to message #175890]

Sat, 07 July 2012 14:53

hnielsen2

Messages: 1434
Registered: February 2004
Location: Alpine CA

Karma: 0

Senior Member

Okay
I need help also.
The field rats bit off the wires right at the opening coming out of the
floor on the outside going to "I think?" the fuel tank switch.
Who has the color code for the fuel switch.
I need to some how find the wires inside the coach and bypass the cut wires.
What a PITA
That's what you get when you live out in the sticks.
Thank You
Howard
Alpine Ca
74 Canyon Lands side bath.

All is well with my Lord

----- Original Message -----
From: "Ken Henderson" <hend4800@bellsouth.net>
To: <gmclist@temp.gmcnet.org>
Sent: Saturday, July 07, 2012 11:58
Subject: Re: [GMCnet] GMC fuel gauge wiring

> Glenn,
>
> Check the wiring diagram and you'll find that the OEM fuel gauge is fed by
> a Gray wire with double black stripes. That wire is in turn fed by either
> the Aux or Main tank sender, dependent upon the position of the fuel tank
> selector switch. In your photo of the connector, the second wires from
> the
> right, in cavity C, should be that Gray w/dbl black wire.
>
> Connect the new gauge to ignition, ground, and that Gray w/dbl black wire
> and you should be good to go -- IF the tank senders are good.
>
> Ken H.
>
>
> On Sat, Jul 7, 2012 at 2:11 PM, Glenn Gardner wrote:
>
>> ...
>
> I have purchased a 0 to 90 ohm fuel gauge and I am very confused about how
>> to connect the wiring to it. The GMC gauge cluster has a plug in wire
>> harness (lots of wires!) to operate all three gauges.
>> On the fuel gauge I purchased, I have three terminals. One for ground,
>> one
>> for ignition switch, and one for the sending unit.
>> ...
>
> I am also attempting to put up a link to a photo of the stock wiring
>> harness to the GMC gauge cluster.
>> photo link : http://www.gmcmhphotos.com/photos/u20658-scooby-doo.html
>> ...
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist

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All is well with my Lord

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Re: [GMCnet] GMC fuel gauge wiring [message #175911 is a reply to message #175898]

Sat, 07 July 2012 16:15

emerystora

Messages: 4442
Registered: January 2004

Karma: 13

Senior Member

On Jul 7, 2012, at 1:53 PM, Howard and Sue wrote:

> Okay
> I need help also.
> The field rats bit off the wires right at the opening coming out of the
> floor on the outside going to "I think?" the fuel tank switch.
> Who has the color code for the fuel switch.
> I need to some how find the wires inside the coach and bypass the cut wires.
> What a PITA
> That's what you get when you live out in the sticks.
> Thank You
> Howard

Howard
Here is something that I had posted in the past that should be of help to you.
------------------------
There are three wires going from the inside wall of the motorhome and through a small hole in the frame and then to the tanks. Actually one of them carries 12 Volts to the tank selector valve when the dash switch is put into AUX tank. The other two wires go to each of the tank senders. Put a small pin through each of the three wires so that you can get a meter on them. Turn on the key and put the dash switch to AUX. Then go to the three wires and use a voltmeter with one lead grounded to your frame and touch each of the three wires so that you can determine which has 12 volts. Pull the pin out of that wire as you know that goes to the tank selector valve.

Then use a jumper wire and ground from one pin to the frame. Check the fuel gauge. If it goes to empty you know that wire is good to the point of the pin and you also know that it goes to the AUX tank (front tank). If nothing happens mover the dash switch to MAIN. The gauge should go to empty and you then know that that wire is the one that goes to the rear or MAIN tank.

Then pull that pin and ground the other pin to the frame. The opposite tank (from the one determined above) should now register empty.

If all of that works as described you now know that the fuel gauge is OK and the wires from the frame to the fuel gauge are OK.

I once had a problem with one tank and found that the one wire going into the wall had been chewed in half by a mouse. The wires run in the wall behind the couch and down to the bottom and out a hole toward the frame. That hole is located right at the left rear of the wall panel behind the couch. I cut a small piece from the corner of the board and I was able to snake a wire down through the hole and splice it into the broken wire and to the wire behind the wall panel.

If the tests above work all right then you know for sure that the problem is between the frame and the top of the tank(s). Good luck.
------------------------

Howard - once you cut out that corner of the panel you will be3 able to get to all three of the wires. If you snake 3 new wires down through the hole that leads under the floor toward the fraoe and which lead to the fuel selector and to the two tank sending units.

The wiring diagram for the 75-76 and for the 77-78 motorhomes show that the black wire leads to the fuel selector switch and should be hot when the dash switch is in the AUX position.

The tan wire leads to the main tank fuel level sender. (rear tank)

The tan wire with two white stripes leads to the Aux fuel tank sender.

I would think that these wire colors would be the same for your 1974.

Emery Stora
77 Kingsley
Frederick, CO
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Re: [GMCnet] GMC fuel gauge wiring [message #175957 is a reply to message #175896]

Sat, 07 July 2012 21:32

David Greenberg

Messages: 222
Registered: September 2010

Karma: 0

Senior Member

Welcome to the group.
I hope you will experience all the good things Jan and I did over our many
GMCing years.

We spent all of 1977 touring the lower 48 with 2 pre teens in a new GMC. In
'93 we bought another GMC with over 400k miles on it and put another 200k
on it.

We made many friends, enjoyed great fellowship, travelled in every state
and province , garnered a lifetime of memories, and learned a lot in the
process.

Jump in with both feet. You and yours will never regret it.

Happy trails!
On Jul 7, 2012 3:39 PM, "Glenn Gardner" <G2photos@aol.com> wrote:

>
>
> Hello Dan,
>
> Thank you for your comments.
> We just got back form our 3rd trip in our GMC.
> We still are getting used to it, and love it more with each trip.
>
> I was just trying to get accurate info from my engine and am currently
> installing quality gauges in our GMC. (A big thanks to Ken H !)
>
> I feel very fortunate to be a member of this GMC community.
> I have already learned so much on this forum, and we have joined the
> Sunshine Statesmen GMC club and have met a handful of their members (all so
> very nice)
>
> I am hoping that next year, the Mrs. & I feel more comfortable going
> futher from home.
> So far we head in any direction, but only 200 or so miles from home. As we
> are more comfortable with the reliability of our GMC we shall stray
> further, and hopefully leave the state of Florida by next year.
> Hope to meet you in person one day. :)
>
> Sincerely,
> Glenn Gardner...G2photosmx.com
> --
> Glenn & Elaine Gardner...
> Miami, Florida...
> 1976 Royale (transmode)
> TZE366V100733
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
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