Gas gauge driving me crazy! - The 1947 - Present Chevrolet & GMC Truck Message Board Network

RShaips · 12-23-2009, 05:11 PM

My gas gauge reads between 1/4 and 1/2 no matter what I do. I have a new tank and new float, have tried 3 different gauges and 3 different sending units. Everything stays the same. When I unhook the tan power wire from the fuse box the gauge goes way past full. I have had the tank out a couple of times also, when I move the float by hand the gauge worked but when it's in it does not. What is going on with this ? Thanks for the help

Critter · 12-23-2009, 05:40 PM

Maybe the wire is (partially) shorted between the sending unit and the fuse panel. Take an Ohm meter and with the tan wire disconnected from the sending unit and the fuse panel and check the wire. You should basically see 0 Ohms resistance. If you see anything else, you have a wiring problem.

cparman · 12-23-2009, 07:33 PM

agree with Critter, but what if you OHM'd the sender? If the sender is stuck in one position, it would give you a constant reading as well. I have been bitten by an aftermarket sender in an aftermarket tank. Disconnect the wire from the sender and ohm it. If the tank is empty, and you have some value above 0 the sender is stuck. HTH

69-72 · 12-23-2009, 10:55 PM

Try turning the key on

Or check your ground, make sure its good and groundy.

Have you changed floats? I replaced my sending unit with a new one and it turned out the float was bad, pinhole leak in the solder, slapped the old one on and it was good to go. I feel for ya, those tanks are a pain to take in and out especially when they are half full.

RShaips · 12-23-2009, 11:29 PM

Well I dropped the tank just far enough to reach in and unplug the wire. It tested fine , so I know that it is good from the tank to the fuse box. I have had the sending unit out a couple of times and the float was good. Yes they are a pain to take in and out, but once you do it several times it gets a little easier!

**Gary 70 Jimmy** · 12-23-2009, 11:56 PM

Make sure you plug the wire in the right place in the fuse box if you plug in the wrong one it will burn up your sending unit the first time you turn the key on. It should be a lower voltage for the sending unit.

AirSpeed · 12-27-2009, 01:17 AM

I had the same problem recently and discovered the circuit board on the back of the gauge assembly was the problem. I found out by pressing on the circuit board near the plug, it turns out the connection was dirty, cleaned it with a little piece of sandpaper and it works perfect now.

Big Block · 01-01-2010, 05:26 PM

Quote:

Originally Posted by Gary 70 Jimmy

Make sure you plug the wire in the right place in the fuse box if you plug in the wrong one it will burn up your sending unit the first time you turn the key on. It should be a lower voltage for the sending unit.

If you plug it into a full 12 volt sorce it will burn up the sending unit!!! It should only read about 9 volts. The gage has a resistor on the back. It may have a short.

RShaips · 01-01-2010, 10:47 PM

Actually I have swapped the resistor 3 times not the sending unit as I said in my first post. It is plugged into the factory spot on the fuse panel. I will try to test the voltage tomorrow, Thanks

Big Block · 01-02-2010, 12:56 PM

Either you don't have a good ground or the sending unit is BAD. I think it may be a bad sending unit. Good luck. I had the same problem with a 72 Suburban. I had a bad sending unit.

RShaips · 01-02-2010, 04:14 PM

I know the ground is good, just waiting for a good reason to take the tank out again!

RShaips · 01-17-2010, 11:25 AM

If my sending unit was bad would the gas gauge move at all? When I go around turns my gauge moves up and down some like it would if it was working. But it still sits at about 1/3 full no matter how much gas is in it. Thanks

AirSpeed · 01-17-2010, 11:41 AM

Have you checked the flexible circuit board connections on the back of the gauge cluster? Mine was behaving just like yours and once I cleaned all the connections it worked perfectly.

RShaips · 01-17-2010, 01:57 PM

The main plug that connects to the gauge cluster I have cleaned. I have actually tried 2 different gauge clusters and pluged it in and had the same result

AirSpeed · 01-18-2010, 12:08 AM

Wow, that us frustrating! Maybe you should bypass all the stock wiring and hook it up directly (unless you already tried that) just to see if there are some wires mixed up in the harness. I don't know if it matters, but is the Gage cluster the same type that came with the truck? Did your truck come with a volt meter, oil pressure gauge? I don't know if they all use the same connector? Looks like you have tried everyting else! Good luck! I know how frustrating it is when wiring doesn't work! Good luck!

12-23-2009, 05:11 PM	#1
RShaips Senior Member Join Date: Jun 2002 Location: Augusta Missouri Posts: 804	Gas gauge driving me crazy! My gas gauge reads between 1/4 and 1/2 no matter what I do. I have a new tank and new float, have tried 3 different gauges and 3 different sending units. Everything stays the same. When I unhook the tan power wire from the fuse box the gauge goes way past full. I have had the tank out a couple of times also, when I move the float by hand the gauge worked but when it's in it does not. What is going on with this ? Thanks for the help

12-23-2009, 05:40 PM	#2
Critter Future TOTM Winner Join Date: Aug 2006 Location: Bulverde, TX Posts: 2,692	Re: Gas gauge driving me crazy! Maybe the wire is (partially) shorted between the sending unit and the fuse panel. Take an Ohm meter and with the tan wire disconnected from the sending unit and the fuse panel and check the wire. You should basically see 0 Ohms resistance. If you see anything else, you have a wiring problem. __________________ 72 Chevy CST K5 HIGHLANDER BLAZER Getting a 6.0,NV4500,NP205,14BFF (Currently laying all over the place in little pieces) 72 Chevy swb step-side "LS" 6.0 Here's a build thread of sorts 2002 HD2500 Crew Cab, 8.1L Allison 4x4 Daily Driver Check it out www.lsdyno.com Last edited by Critter; 12-23-2009 at 05:41 PM.

12-23-2009, 07:33 PM	#3
cparman sharp as a marble Join Date: Jan 2007 Location: atlantic beach,florida Posts: 1,082	Re: Gas gauge driving me crazy! agree with Critter, but what if you OHM'd the sender? If the sender is stuck in one position, it would give you a constant reading as well. I have been bitten by an aftermarket sender in an aftermarket tank. Disconnect the wire from the sender and ohm it. If the tank is empty, and you have some value above 0 the sender is stuck. HTH

12-23-2009, 10:55 PM	#4
69-72 Registered User Join Date: May 2008 Location: 204 Posts: 903	Re: Gas gauge driving me crazy! Try turning the key on Or check your ground, make sure its good and groundy. Have you changed floats? I replaced my sending unit with a new one and it turned out the float was bad, pinhole leak in the solder, slapped the old one on and it was good to go. I feel for ya, those tanks are a pain to take in and out especially when they are half full. __________________ 1969 Chevy Custom Camper 3/4 ton Rust free survivor 1972 Chevy Blazer CST 4x4 Almost Rust free survivor 1972 GMC Jimmy 2wd Undergoing surgery Last edited by 69-72; 12-23-2009 at 10:59 PM.

12-23-2009, 11:29 PM	#5
RShaips Senior Member Join Date: Jun 2002 Location: Augusta Missouri Posts: 804	Re: Gas gauge driving me crazy! Well I dropped the tank just far enough to reach in and unplug the wire. It tested fine , so I know that it is good from the tank to the fuse box. I have had the sending unit out a couple of times and the float was good. Yes they are a pain to take in and out, but once you do it several times it gets a little easier!

12-23-2009, 11:56 PM	#6
Gary 70 Jimmy Senior Member Join Date: Jan 2002 Location: Burghill, Ohio 44404 Posts: 3,402	Re: Gas gauge driving me crazy! Make sure you plug the wire in the right place in the fuse box if you plug in the wrong one it will burn up your sending unit the first time you turn the key on. It should be a lower voltage for the sending unit. __________________ 1972 GMC Jimmy 1/2 4X4 4wheel camper 1970 GMC Jimmy 1/2 4X4 350 1969 Chevy Blazer 1/2 4X4 307 1967 chevy LWB 3/4 396

12-27-2009, 01:17 AM	#7
AirSpeed Registered User Join Date: Jul 2007 Location: Fall River California Posts: 2,026	Re: Gas gauge driving me crazy! I had the same problem recently and discovered the circuit board on the back of the gauge assembly was the problem. I found out by pressing on the circuit board near the plug, it turns out the connection was dirty, cleaned it with a little piece of sandpaper and it works perfect now.

01-01-2010, 10:47 PM	#9
RShaips Senior Member Join Date: Jun 2002 Location: Augusta Missouri Posts: 804	Re: Gas gauge driving me crazy! Actually I have swapped the resistor 3 times not the sending unit as I said in my first post. It is plugged into the factory spot on the fuse panel. I will try to test the voltage tomorrow, Thanks

01-02-2010, 12:56 PM	#10
Big Block Big Block Join Date: Mar 2005 Location: Durham, N.C. Posts: 1,649	Re: Gas gauge driving me crazy! Either you don't have a good ground or the sending unit is BAD. I think it may be a bad sending unit. Good luck. I had the same problem with a 72 Suburban. I had a bad sending unit.

01-02-2010, 04:14 PM	#11
RShaips Senior Member Join Date: Jun 2002 Location: Augusta Missouri Posts: 804	Re: Gas gauge driving me crazy! I know the ground is good, just waiting for a good reason to take the tank out again!

01-17-2010, 11:25 AM	#12
RShaips Senior Member Join Date: Jun 2002 Location: Augusta Missouri Posts: 804	Re: Gas gauge driving me crazy! If my sending unit was bad would the gas gauge move at all? When I go around turns my gauge moves up and down some like it would if it was working. But it still sits at about 1/3 full no matter how much gas is in it. Thanks

01-17-2010, 11:41 AM	#13
AirSpeed Registered User Join Date: Jul 2007 Location: Fall River California Posts: 2,026	Re: Gas gauge driving me crazy! Have you checked the flexible circuit board connections on the back of the gauge cluster? Mine was behaving just like yours and once I cleaned all the connections it worked perfectly.

01-17-2010, 01:57 PM	#14
RShaips Senior Member Join Date: Jun 2002 Location: Augusta Missouri Posts: 804	Re: Gas gauge driving me crazy! The main plug that connects to the gauge cluster I have cleaned. I have actually tried 2 different gauge clusters and pluged it in and had the same result

01-18-2010, 12:08 AM	#15
AirSpeed Registered User Join Date: Jul 2007 Location: Fall River California Posts: 2,026	Re: Gas gauge driving me crazy! Wow, that us frustrating! Maybe you should bypass all the stock wiring and hook it up directly (unless you already tried that) just to see if there are some wires mixed up in the harness. I don't know if it matters, but is the Gage cluster the same type that came with the truck? Did your truck come with a volt meter, oil pressure gauge? I don't know if they all use the same connector? Looks like you have tried everyting else! Good luck! I know how frustrating it is when wiring doesn't work! Good luck!



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