Gas Gauge - The 1947 - Present Chevrolet & GMC Truck Message Board Network

mrmojo32 · 02-05-2007, 10:32 AM

Hey everyone...

I just bought a 72 Chevy LWB - 6 cyl - manual trans.

The gas gauge is not working. Can I get any tips in trouble shooting this?

Thanks in advance.

**LockDoc** · 02-05-2007, 11:06 AM

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This should get you started......

http://67-72chevytrucks.com/vboard/s...ght=fuel+guage

http://67-72chevytrucks.com/vboard/s...ght=fuel+guage

http://67-72chevytrucks.com/vboard/s...ght=fuel+guage

http://67-72chevytrucks.com/vboard/s...ght=fuel+guage

http://67-72chevytrucks.com/vboard/s...ght=fuel+guage

And with any luck at all.... finished...

LockDoc

cstm68 · 02-05-2007, 12:40 PM

could be a bad sending unit

mnunn454 · 02-05-2007, 10:09 PM

I trouble shot mine and found the gauge to be working fine and the sending unit to be bad.

The way I determined this was just to disconnect the tan wire that runs to the tank sending unit and touch it to ground. As I recall (It's been 18 months ago), the gauge read full when it was ungrounded and empty when I grounded it, so I knew the gauge was working (I may have this backwards).

I then pulled the 40 year old sending unit out of the tank and at least half of the fine copper resistance wires were all gone.

MT1972cheyenne · 02-05-2007, 10:34 PM

First place to check is for a damaged tan wire under the drivers sill plate.

mrmojo32 · 03-05-2007, 07:31 PM

Ok... Thanks for all the help so far.

My gauge sits on 1/4 tank regardless of how much is in there. I disconnected the one wire that goes to the tank and there is no difference. I grounded that same wire and no difference. I hooked it all back up and grounded the tank and no difference. Then grounded the gauge and no difference.

I have a spare instrument cluster that I hooked up and there is the same problem but this one sits on 1/8 tank with no movement.

All other gauges are doing fine.

Any Ideas? THanks!

mnunn454 · 03-05-2007, 07:55 PM

Sounds to me like no power's getting to the gage. Where does the needle sit when the key is off?

When you grounded the gage (above) did you disconnect the tan wire from the back of it 1st?

Also, while you have the tan wire off of the gage, try hooking it to the ohmmeter and measuring the resistance. Should read read somewhere between 0 and 600 ohms. If it does, that eliminates the sending unit or wiring and narrows it to the gas gage or it's power supply.

mrmojo32 · 03-05-2007, 10:02 PM

Ok.. Needle is at 1/8th to 1/4th at all times, even when ignition is off. The needle never moves.

I have never disconnected the tan wire from the gauge. Only from the tank. There is a large plug that connects to the back of the instrument cluster only.

Sorry if I am being unclear about some of this, but it really has me stumped.

mrmojo32 · 03-06-2007, 06:38 AM

any ideas?

02-05-2007, 10:32 AM	#1
mrmojo32 Registered User Join Date: Jan 2007 Location: Louisiana Posts: 216	Gas Gauge Hey everyone... I just bought a 72 Chevy LWB - 6 cyl - manual trans. The gas gauge is not working. Can I get any tips in trouble shooting this? Thanks in advance.

02-05-2007, 11:06 AM	#2
LockDoc The Older Generation Join Date: Aug 2006 Location: Montezuma, Iowa Posts: 25,818	Re: Gas Gauge - This should get you started...... http://67-72chevytrucks.com/vboard/s...ght=fuel+guage http://67-72chevytrucks.com/vboard/s...ght=fuel+guage http://67-72chevytrucks.com/vboard/s...ght=fuel+guage http://67-72chevytrucks.com/vboard/s...ght=fuel+guage http://67-72chevytrucks.com/vboard/s...ght=fuel+guage And with any luck at all.... finished... LockDoc __________________ Leon Locksmith, Specializing In Antique Trucks, Automobiles, & Motorcycles (My Dually Pickup Project Thread) http://67-72chevytrucks.com/vboard/s...d.php?t=829820 -

02-05-2007, 12:40 PM	#3
cstm68 Registered User Join Date: Jan 2007 Location: shoreline, wa Posts: 1,565	Re: Gas Gauge could be a bad sending unit

02-05-2007, 10:09 PM	#4
mnunn454 Registered User Join Date: Dec 2006 Location: Rhode Island Posts: 602	Re: Gas Gauge I trouble shot mine and found the gauge to be working fine and the sending unit to be bad. The way I determined this was just to disconnect the tan wire that runs to the tank sending unit and touch it to ground. As I recall (It's been 18 months ago), the gauge read full when it was ungrounded and empty when I grounded it, so I knew the gauge was working (I may have this backwards). I then pulled the 40 year old sending unit out of the tank and at least half of the fine copper resistance wires were all gone. __________________ 69 C-10 SWB Fleetside 454/TH400 (For Sale) http://67-72chevytrucks.com/vboard/c...ct=1299&cat=12 70 El Camino 454 TH700 29 Model A 4-DR Sedan Deluxe

02-05-2007, 10:34 PM	#5
MT1972cheyenne Registered User Join Date: Dec 2006 Location: Montana Posts: 223	Re: Gas Gauge First place to check is for a damaged tan wire under the drivers sill plate.

03-05-2007, 07:31 PM	#6
mrmojo32 Registered User Join Date: Jan 2007 Location: Louisiana Posts: 216	Re: Gas Gauge Ok... Thanks for all the help so far. My gauge sits on 1/4 tank regardless of how much is in there. I disconnected the one wire that goes to the tank and there is no difference. I grounded that same wire and no difference. I hooked it all back up and grounded the tank and no difference. Then grounded the gauge and no difference. I have a spare instrument cluster that I hooked up and there is the same problem but this one sits on 1/8 tank with no movement. All other gauges are doing fine. Any Ideas? THanks!

03-05-2007, 07:55 PM	#7
mnunn454 Registered User Join Date: Dec 2006 Location: Rhode Island Posts: 602	Re: Gas Gauge Sounds to me like no power's getting to the gage. Where does the needle sit when the key is off? When you grounded the gage (above) did you disconnect the tan wire from the back of it 1st? Also, while you have the tan wire off of the gage, try hooking it to the ohmmeter and measuring the resistance. Should read read somewhere between 0 and 600 ohms. If it does, that eliminates the sending unit or wiring and narrows it to the gas gage or it's power supply. __________________ 69 C-10 SWB Fleetside 454/TH400 (For Sale) http://67-72chevytrucks.com/vboard/c...ct=1299&cat=12 70 El Camino 454 TH700 29 Model A 4-DR Sedan Deluxe Last edited by mnunn454; 03-05-2007 at 07:56 PM.

03-05-2007, 10:02 PM	#8
mrmojo32 Registered User Join Date: Jan 2007 Location: Louisiana Posts: 216	Re: Gas Gauge Ok.. Needle is at 1/8th to 1/4th at all times, even when ignition is off. The needle never moves. I have never disconnected the tan wire from the gauge. Only from the tank. There is a large plug that connects to the back of the instrument cluster only. Sorry if I am being unclear about some of this, but it really has me stumped.

03-06-2007, 06:38 AM	#9
mrmojo32 Registered User Join Date: Jan 2007 Location: Louisiana Posts: 216	Re: Gas Gauge any ideas?



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