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#1 | |
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:
You can use a 100 ohm resistor from Radio Shack but the stock style are much easier to install and there are plenty out there available. Thanks for your in put on the subject, Take care, Tom |
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#2 |
Registered User
Join Date: May 2017
Location: Hot Springs Village, AR
Posts: 3
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
This is great information. I have been fighting with the fuel gauge on my 72 C10 for 2 months and getting nowhere. I replaced the tank sending unit which did not help. I just did the diagnostics in your post and got the following readings.
Picture 1 - 44.4 ohms I read 23.4 ohms Picture 2 - 98.2 ohms I read 23.3 ohms Picture 3 - 142.8 ohms I read 2.2 ohms My best guess is a bad resistor. Do you agree? If so, where can I buy a new resistor. If I'm wrong, please advise next steps. Thanks so much. |
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#3 |
Registered User
Join Date: May 2011
Location: Reno Nevada
Posts: 380
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
I also have found that time to time the resistors fail.
With what you indicate I would believe your problem is in the resistor. . They are available on this site. Good luck. Vic |
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#4 |
Registered User
Join Date: May 2017
Location: Hot Springs Village, AR
Posts: 3
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
Thanks Vic,
I'll see if I can find the resistor. You said they are available on this site. Are you talking about 67-72chevytrucks.com? I don't see anywhere to buy them. Thanks again. Ron |
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#5 |
Registered User
Join Date: May 2017
Location: Hot Springs Village, AR
Posts: 3
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
Does anyone have a source for the fuel gauge resistor on a 72 C`10?
Thanks, Ron |
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#6 | |
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:
Send me a PM with your address information and I will send you a good resistor. Typically the main problem when the resistor goes bad is you will never register more than 1/4 tank no matter how much fuel you have. I don't see what photos you are refering to but the stock fuel gauge resistors will read around 90-100 ohms. The 23.3 ohms you have would only get your gauge up to 1/4 tank based on 90 ohms at full, 45 ohms at half and 22.5 ohms at 1/4 tank. Hope this helps, let me know, Tom |
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#7 |
Registered User
Join Date: Aug 2017
Location: San Diego,CA
Posts: 7
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
Hi guys, this is my first post and the fuel gauge in my blazer is driving me nuts.
I purchased a new gauge and sender for the blazer and did all the testing shown on page 1 of this post. Everything was spot on with the readings so I decided to go ahead and hook everything up while on my bench. at .8 ohm's the tank read empty. as the ohm's increased the needle on the gauge started to move, but once I raised the float arm to 1/4 or 22.5 ohm's the needle was already on full. If I lift the float arm anymore than 1/4 tank the needle continues past full. The sender reads true and so does the gauge. The other bummer is I had to install everything in the blazer so I could not only use the vehicle but know when to get gas. when the needle starts to drop below full, I find a gas station quick. any ideas would be great. Mark |
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#8 | |
Registered User
Join Date: Dec 2011
Location: Brandon, Manitoba, Canada
Posts: 546
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
Quote:
__________________
Bob 1967 2wd Burb, 350/TH350, 3.73 posi |
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#9 |
Registered User
Join Date: Aug 2017
Location: San Diego,CA
Posts: 7
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
Hi Bob, yes float all the way up reads 90 ohm's.
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#10 |
Registered User
Join Date: Dec 2011
Location: Brandon, Manitoba, Canada
Posts: 546
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
That sender will work properly with a GM gauge. What gauge did you buy? It sounds like it is not a match with your sender.
__________________
Bob 1967 2wd Burb, 350/TH350, 3.73 posi |
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#11 |
Registered User
Join Date: Aug 2017
Location: San Diego,CA
Posts: 7
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
i purchased a stock replacement gauge for my 72 blazer.
Mark |
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#12 |
Registered User
Join Date: Aug 2017
Location: San Diego,CA
Posts: 7
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
Tom, I purchased the new fuel gauge from Brothers. Part #GGE1001 nothing was removed to my knowledge. I will try removing the resistor and let you know.
Mark Last edited by Sparkys66; 08-19-2017 at 03:09 PM. |
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#13 | |
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 brothers and ask if it requires an external resistor or if it is built into the gauge. I can sell you a decent used fuel gauge for $25.00 shipped that would be tested and working. Or I would check with Brothers and see if they can send you a new one. These are not complicated. They need battery voltage, ground and a signal from the fuel sender to work. It sounds like you have done your home work and possibly just got a bad gauge from Brothers. Hope this helps. |
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#14 |
Registered User
Join Date: Aug 2017
Location: San Diego,CA
Posts: 7
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
Thank you Tom, removed the resistor and the gauge now reads 1/4 with 5 gallons of gas in the tank. i will go top off the tank later today and see what happens.
Mark |
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#15 |
Registered User
Join Date: Aug 2017
Location: San Diego,CA
Posts: 7
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
Thank you Bob for taking time out of your day to help with this issue.
Mark |
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#16 |
Registered User
Join Date: Dec 2011
Location: Brandon, Manitoba, Canada
Posts: 546
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
Not a problem, Mark. Glad to help. Let us know how it turns out.
__________________
Bob 1967 2wd Burb, 350/TH350, 3.73 posi |
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#17 |
Registered User
Join Date: Aug 2017
Location: San Diego,CA
Posts: 7
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
Works perfect now. gauge read 1/4, added 17 gallons, now reads full.
Mark |
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#18 |
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
Good stuff here. Glad We are able to help each other get through these gremlins.
![]() Take care, Tom |
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#19 |
Registered User
Join Date: Feb 2012
Location: Ruskin Florida
Posts: 4,560
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
Sure helped me out! Thank You cluster king!
__________________
70 swb 4x4 406sbc 700r4 203/205 d60/14blt locker yadda yadda http://67-72chevytrucks.com/vboard/s...88#post6935688 Yeller 72 Blazer 2wd conversion project "No Daggum Money" http://67-72chevytrucks.com/vboard/s...d.php?t=550804 LS1-T56 3.73 LSD super budget build Blanco-2014 Sierra SWB https://67-72chevytrucks.com/vboard/...d.php?t=810350 |
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#20 |
Registered User
Join Date: Jul 2015
Location: Vacaville CA
Posts: 153
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
This is a great write up however I am having a slightly different problem. I know my sender works as it is new and tested. My fuel gauge just moves erratically, it goes from being correct to way past full for a few minutes then back to correct and it may stay there or it may go down to empty then back to past full to correct again. There is no rhyme or reason to this, it just moves all over the place. is it a bad ground? Where should I ground the gauge to make sure I have a good ground?
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#21 | |
Registered User
Join Date: Dec 2011
Location: Brandon, Manitoba, Canada
Posts: 546
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
Quote:
__________________
Bob 1967 2wd Burb, 350/TH350, 3.73 posi |
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#22 |
Registered User
Join Date: Jul 2015
Location: Vacaville CA
Posts: 153
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
I have a good ground on the sender so I believe the problem is a bad ground on the gauge. I'm just not sure how the gauge should be grounded, from one of gauge terminals?
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#23 | |
Msgt USAF Ret
![]() ![]() Join Date: Jan 2005
Location: Kalamazoo, Michigan
Posts: 8,714
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
Quote:
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VetteVet metallic green 67 stepside 74 corvette convertible 1965 Harley sportster 1995 Harley wide glide Growing old is hell, but it beats the alternative. |
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#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
Quote:
Check all the 5/16 nuts on the back and make sure all are tight. It sounds like a loose ground or bad connection to me. Share what you find here please. 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 |
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#25 |
Registered User
Join Date: Jul 2012
Location: New Orleans, LA
Posts: 184
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Re: 67-72 Chevy Truck fuel gauge diagnostics 101
Subscribing
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1972 K10, 350/SM465/NP205, 4 inch lift, 35x12.50s on 15x10 wheels 1976 K20 crew cab, 350/Ranger/SM465/NP205 |
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