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12-02-2018, 08:34 PM
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#1 |
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Registered User
Join Date: Oct 2015
Location: Ocala, FL
Posts: 18
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Gas Gauge Voltage
I'm debugging a fuel gauge error and found the voltage at the stock fuse panel spade terminal for "Gas Gauge" is only 7.8 volts. My tank resistance on a 30 ohm sending unit is correct at the current fill level: 26.7 ohms at 3/4 full. However, I cannot get an empty gauge reading grounding the sending unit wire. It will go to max gauge reading disconnected and key on however.
The 7.8 volts is puzzling. Should it be 12+ volts? Thanks for all the help! |
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12-02-2018, 09:30 PM
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#2 |
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Senior Member
 
Join Date: Jan 2011
Location: Hayes Va
Posts: 4,569
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Re: Gas Gauge Voltage
The low voltage is either a bad ground or a corroded terminal driving the resistance up causing the voltage drop.
Jimmy
__________________
60 to 66 Chevy and GMC window decals http://67-72chevytrucks.com/vboard/s...d.php?t=661131 Good friends, good food and a hotrod what else do you need? 1966 BBW long fleet Daily driver 1965 BBW short fleet Sold and going to a good home 1965 Suburban 2003 3500 Duramax 2005 Ultra Classic |
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12-03-2018, 09:36 AM
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#3 |
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Registered User
Join Date: Oct 2015
Location: Ocala, FL
Posts: 18
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Re: Gas Gauge Voltage
Is the resistor pad across the positive and sending wire terminals common on early gauges giving me the 7.8 volts possibly? I pulled the fuse next to the terminal, cleaned/sanded the posts and installed a new fuse with dielectric grease to ensure a good connection. While the fuse was out, I checked the voltage at the spade and, again, 7.8 volts. Total frustration.
Thanks again for the help. Doug |
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12-19-2018, 10:16 PM
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#4 |
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Cluster King
Join Date: Nov 2012
Location: Junction City, OR
Posts: 5,263
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Re: Gas Gauge Voltage
So you have a fuel gauge that has power, ground and a signal wire.
The power wire is the pink one and should have battery voltage with the key on. The signal wire will show voltage and that voltage will be resisted voltage from the sending unit depending on how much fuel is in the tank. If you had the sending unit out of the tank and moved the float, it should change the voltage on the signal wire, which is the tan one. The ground comes through the cluster itself. Can you tell me what the actual issue is? 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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12-20-2018, 05:19 AM
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#5 |
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Registered User
Join Date: Oct 2015
Location: Ocala, FL
Posts: 18
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Re: Gas Gauge Voltage
I had replaced the original gauge with "Shanghai Junk" and could not get the gauge to "0" reading when grounding the panel wire. Sent the original gauge to Williamson's for repair and all is good now.
Had a "Shanghai Junk" repop tach same issue. Williamson got it working. Shame on me for twice buying off-shore. We have no choice sometimes but to add to our landfills. Thank you for the reply and Merry Christmas Doug |
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12-23-2018, 01:39 AM
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#6 |
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Registered User
Join Date: Mar 2010
Location: thomastown mississippi
Posts: 1,261
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Re: Gas Gauge Voltage
Doug who is "Williamson's"?
Thanks |
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12-23-2018, 05:23 AM
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#7 |
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Registered User
Join Date: Oct 2015
Location: Ocala, FL
Posts: 18
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Re: Gas Gauge Voltage
Williamson's Instruments in Chester, Arkansas. Great people.
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