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02-07-2018, 11:46 PM | #1 | |
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Join Date: May 2017
Location: Carpinteria, Ca
Posts: 5
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Quote:
Posted via Mobile Device Edit: reason I ask is that my fuel gauge (71 Blazer) is stuck below empty, I noticed printed Circuit was burned out on ground circuit next to plug in. Replaced circuit and it burnt out again. Turn signals are also permanently lit.. Grateful for any advice I’m stumped. Ben Last edited by CarpBlazer; 02-08-2018 at 12:09 AM. Reason: More info |
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02-08-2018, 12:14 AM | #2 | |
Cluster King
Join Date: Nov 2012
Location: Junction City, OR
Posts: 5,263
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
Quote:
While doing my testing, I have fried a few by shorts and that is the spot the burn through. Maybe some of the others have some ideas. I know it is hard to keep good ones around for long
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Contact me on all of your gauge cluster needs. I specialize in restoration, repair and parts sales for 67-72 Chevy and GMC trucks. email me at tbonegarris@yahoo.com I am also a dealer for Counterpart for gauge cluster parts only. Also see my facebook page, CG&C |
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02-10-2018, 03:58 PM | #3 |
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Join Date: Jul 2015
Location: Vacaville CA
Posts: 153
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
Thank you everyone for your input! It turns out I too have a burned out circuit board. When I reached up to feel what looked like a bad spot, I heard an arc so the battery is disconnected until the new circuit board is installed.
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02-14-2018, 08:02 PM | #4 |
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Join Date: May 2017
Location: Carpinteria, Ca
Posts: 5
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
Ok, so I figured out my electrical gremlin causing stuck fuel gauge below empty. I was having issues with all dash lights (turn signals solid, high beam indicator lit, everything that could light up on dash)to go on when ignition on and as I said above, fuel gauge was stuck below zero.
After checking the whole harness, replacing circuit board (only to fry the ground connection again) and hours of scratching my head..I realized the factory tach hot wire was running from fuse box ‘ignition unfused’ port to the upper center post on the tach. Problem is, that upper post is the ground post..Face palm...I attached it to ground and boom, everything works. Fuel gauge is now working perfectly. I’m now on a mission to find correct wiring for factory tach. This thread really helped me tackle all this and get it solved, Thanks! Ben |
03-06-2018, 11:13 PM | #5 | |
Cluster King
Join Date: Nov 2012
Location: Junction City, OR
Posts: 5,263
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
Quote:
Did you get the tach figured out? Pretty simple to wire up. Let me know if you need help with it. With face in palm, looking at the back, 12v is on the right, coil on the left and ground is the center stud which would only be used if the tach is not getting a good ground through the tin(s). Tom
__________________
Contact me on all of your gauge cluster needs. I specialize in restoration, repair and parts sales for 67-72 Chevy and GMC trucks. email me at tbonegarris@yahoo.com I am also a dealer for Counterpart for gauge cluster parts only. Also see my facebook page, CG&C |
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03-07-2018, 11:39 AM | #6 |
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Join Date: May 2017
Location: Carpinteria, Ca
Posts: 5
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
Yes, from the previous tach wiring debacle, I fried one of the grounds in the printed circuit so decided to add a ground from the center stud at the tach to dash and all works great. Thanks for your help!
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03-07-2018, 06:03 PM | #7 |
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Join Date: Apr 2017
Location: Colorado Springs
Posts: 129
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
Just read this entire thing, plus a few other threads on fuel gauge stuff. Followed the steps for troubleshooting and narrowed it down to a sunk float on my sending unit. Everything is working as it should now. Thank you everyone for the awesome information. Saved me a lot of time and headache.
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03-23-2018, 01:00 AM | #8 | |
Cluster King
Join Date: Nov 2012
Location: Junction City, OR
Posts: 5,263
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
Quote:
Yes, thank you everyone who adds there experience here. Take care, Tom
__________________
Contact me on all of your gauge cluster needs. I specialize in restoration, repair and parts sales for 67-72 Chevy and GMC trucks. email me at tbonegarris@yahoo.com I am also a dealer for Counterpart for gauge cluster parts only. Also see my facebook page, CG&C |
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04-08-2018, 12:41 PM | #9 |
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Join Date: Jun 2017
Location: port st lucie, fl
Posts: 28
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
I know this is an old post but I hope someone will direct me a little bit. Not being great at electrical work I have read the previous threads and checked some things out with my gas gauge. Let me start and say that the gauged worked fine before I removed the cluster to change the printed circuit on the back in order to get my dash lights working. When I reinstalled it the gauge was reading at three o'clock. I then reached up behind the dash and found out that I haven't tighten the nuts down on the gauge terminals. I don't know if I had the key on or not but as I was tightening the nuts the gauge went from 3 o'clock to 3/4 full and hasn't moved since. I checked the resistance at the tank and got 68 which is what I think is correct for the gas I think is in the tank. When I remove the tan wire from the fuse box nothing happens to the gauge. When I grounded the terminal nothing happens with the gauge. Did I blow the resistor when I was tightening the nuts up I'm stumped
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04-08-2018, 02:11 PM | #10 | |
Cluster King
Join Date: Nov 2012
Location: Junction City, OR
Posts: 5,263
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
Quote:
If the temp gauge does not work, check for battery voltage at the #3 terminal of the cluster connector. You should have voltage with key on. If not, check the gauge fuse. Also it is critical that the circuit board tangs where the connector plugs in have not moved and caused a short. Over years they do come loose. Yu can repair with a dab of super glue if needed. If you suspect the resistor is bad, remove it from the gauge and test it with an ohm meter from one side to the other. You should have approx 85 ohms. The gauge will set at the 3 oclock poistion when it looses ground or the tan wire is not connected, which is the signal wire from the sender. The gauge will stay where ever it stopped after ign is shut off or the gauge looses battery voltage. Hope this helps, Tom
__________________
Contact me on all of your gauge cluster needs. I specialize in restoration, repair and parts sales for 67-72 Chevy and GMC trucks. email me at tbonegarris@yahoo.com I am also a dealer for Counterpart for gauge cluster parts only. Also see my facebook page, CG&C |
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04-09-2018, 08:36 PM | #11 | |
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Join Date: Jun 2017
Location: port st lucie, fl
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
Quote:
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04-09-2018, 11:11 PM | #12 | |
Cluster King
Join Date: Nov 2012
Location: Junction City, OR
Posts: 5,263
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
Quote:
__________________
Contact me on all of your gauge cluster needs. I specialize in restoration, repair and parts sales for 67-72 Chevy and GMC trucks. email me at tbonegarris@yahoo.com I am also a dealer for Counterpart for gauge cluster parts only. Also see my facebook page, CG&C |
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04-15-2018, 02:57 PM | #13 |
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Join Date: Dec 2016
Location: Lethbridge AB
Posts: 22
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
I may need therapy before this task is accomplished...
Gauge is at 3 o'clock position.. new tank/sending unit/ wires go all they way into the cab..proper ground.(LMC under bed tank) pull the brown wire clip out of the fuse block and it reads 92 ohms with a full tank of gas. plug the clip back into the fuse block an check it while plugged in..32 ohms..back feed? I have 12.6 volts at the #3 on the plug with the key on. the battery and temperature gauge is disconnected. after market gauges installed oil/volts/temp. Last edited by Shotgunn; 04-15-2018 at 03:37 PM. |
04-23-2018, 11:21 PM | #14 |
Msgt USAF Ret
Join Date: Jan 2005
Location: Kalamazoo, Michigan
Posts: 8,716
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
The wire from the tank sending unit terminal goes to the FUEL terminal on the fuse panel. It is located on the middle terminal on the end of the panel.
It's on the right end center terminal of this panel. This is just a connector for the sender wire to the fuel gauge which exits out the rear of the fuse panel and goes to the dash cluster plug to pin 4.
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08-20-2018, 11:11 PM | #15 |
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Join Date: Aug 2018
Location: San Luis Obispo
Posts: 4
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
My fuel gauge doesn't move and it is below the empty mark. I pulled the resistor from the back of the fuel gauge and it doesn't give any readings with the multi-meter. I also checked the printed circuit and it looks like it is in pretty good shape. Would the resistor cause the gauge to not move at all? Could the fuel gauge just not be receiving voltage? The rest of the lights in the instrument panel work but the brake light only lights up when the engine is starting. The fuel gauge doesn't move though.
Any help would be greatly appreciated. |
08-26-2018, 04:30 PM | #16 | |
Cluster King
Join Date: Nov 2012
Location: Junction City, OR
Posts: 5,263
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
Quote:
I would take a good look at the back of the circuit board and make sure the path for power is not burnt. You can use a test light and check for power right at the gauge itself. The resistor should show some resistance. You should get around 85/90 ohms from a good working resistor. If not, replace it and see what happens. Hope this helps, Let me know, Tom
__________________
Contact me on all of your gauge cluster needs. I specialize in restoration, repair and parts sales for 67-72 Chevy and GMC trucks. email me at tbonegarris@yahoo.com I am also a dealer for Counterpart for gauge cluster parts only. Also see my facebook page, CG&C |
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08-29-2018, 01:53 PM | #17 |
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Join Date: May 2017
Location: Helena, MT
Posts: 80
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
Glad I stumbled into this thread- my fuel gauge (previously working great) just went to full 3 O'clock and won't budge. Last night I started simple- pulling the tan wire from the sending unit- noticed as I moved it up or down on the sending unit post the fuel gauge bounced to just below 'F' and then back to 2-3 O'clock.
Appears my tank is grounded to frame. Might try a jumper ground wire from sending unit to frame- see what happens. Great thread, btw- appreciate the information very much. |
08-30-2018, 10:51 AM | #18 |
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Join Date: Aug 2018
Location: San Luis Obispo
Posts: 4
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
Does anyone know where you can get replacement resistors for the back of the fuel gauge?
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10-05-2018, 02:24 AM | #19 |
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Join Date: Oct 2018
Location: Winchester Tennessee
Posts: 21
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
I also would like to know where I can get the resistor needed for the gas gauge. Thank you in advance
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10-05-2018, 10:00 AM | #20 |
Registered User
Join Date: Aug 2018
Location: San Luis Obispo
Posts: 4
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
http://www.truckandcarshop.com/
The online catalog is a little slow but its in there. TBONE1964 hooked me up with this site. I replaced mine and my fuel gauge started working again. Before I replaced the resistor, the gauge was way below empty and didn't move. It was a much easier option than pulling the sending unit to check it out. |
10-05-2018, 10:31 AM | #21 |
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Join Date: Oct 2018
Location: Winchester Tennessee
Posts: 21
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
Thank you heyfish. The part number at truckandcarshop is 67-04508.
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07-11-2019, 10:03 PM | #22 |
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Join Date: Feb 2019
Location: So Cal, CA
Posts: 108
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
Resurrecting a very nice thread as I have been searching for awhile, gave up, searched again yada yada. I was guessing my ground went bad at the tank, as my gauge is stuck at 3 o'clock spot. I just got the truck up and running (been sitting awhile) and decided to wait on messing with the gauge as I have active spider webs all over, so trying to get a good steam cleaning before I go reaching into dark areas.
Anyways, I was trying to install a lap belt so I can drive to a vehicle lift and steam clean the underside. I accidently found a tan wire, taped all up and tucked in my cab corner. Is this my ground wire? Can I ground this side and check my gauge? Edit-i have 2 saddle tanks. Is there a separate wire for the right side tank? I have no idea if it works. My selector valve is stuck/broke in the left tank position
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11-02-2019, 03:12 PM | #23 |
Cluster King
Join Date: Nov 2012
Location: Junction City, OR
Posts: 5,263
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
Hello guys and gals,
I am going to add some information from a bench test I did today. This is going to show how to wire a fuel gauge loose from the cluster and test. I will try and make it basic and clear as to what is going on for each photo. This will take some tome so let me get everything loaded before responding please. I try to keep up with this but very busy with other things. I appreciate anyone who chimes in with good info from their own experience. Thank you, Tom
__________________
Contact me on all of your gauge cluster needs. I specialize in restoration, repair and parts sales for 67-72 Chevy and GMC trucks. email me at tbonegarris@yahoo.com I am also a dealer for Counterpart for gauge cluster parts only. Also see my facebook page, CG&C |
11-02-2019, 03:24 PM | #24 |
Cluster King
Join Date: Nov 2012
Location: Junction City, OR
Posts: 5,263
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
I am using a new AC Delco fuel gauge and a GM 0-90 ohm sending unit.
These photos show how the gauge is wired to the sender and I use a 10 amp batt charger for power. The ground can be shared between the sender and the gauge. I use a yellow jumper as the "tan" wire that runs from sender to fuse panel and then to cluster. I use green lead from my batt charger for the pink power wire from the ignition switch through the fuse panel and to the circuit board in location number 3 on the connector. It is really this simple. If you can do this, you can test your fuel gauge out of the cluster.
__________________
Contact me on all of your gauge cluster needs. I specialize in restoration, repair and parts sales for 67-72 Chevy and GMC trucks. email me at tbonegarris@yahoo.com I am also a dealer for Counterpart for gauge cluster parts only. Also see my facebook page, CG&C |
11-02-2019, 03:28 PM | #25 |
Cluster King
Join Date: Nov 2012
Location: Junction City, OR
Posts: 5,263
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
This photo shows the ohm reading (NO POWER / IGN OFF) across the resistor when installed. 42.7 ohms. It will be in the area of 85 ohms when the resistor is loose from the gauge.
__________________
Contact me on all of your gauge cluster needs. I specialize in restoration, repair and parts sales for 67-72 Chevy and GMC trucks. email me at tbonegarris@yahoo.com I am also a dealer for Counterpart for gauge cluster parts only. Also see my facebook page, CG&C |
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