Gas Gauge or Sending Unit? - Team Camaro Tech
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post #1 of 10 (permalink) Old Sep 27th, 09, 04:25 PM Thread Starter
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Gas Gauge or Sending Unit?

I have read several of the post about trouble shooting gas guage problems...still can't figure mine out.

I have a 69 Camaro with console gauges...everything was working fine untill a recent trip and the hand pegged out on full. The hand will drop to about 3/4 after a few seconds with the key off...then pegs back out with key on. I checked the ground from the sending unit to trunk floor brace. I also tried grounding the tan wire in the trunk harness and the gauge still reads full. J


Just trying to determine if it is the gauge or the sending unit. Draining the tank right now to get ready to drop and check the wire to the top of the sending unit.
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post #2 of 10 (permalink) Old Sep 27th, 09, 04:30 PM
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Re: Gas Gauge or Sending Unit?

Disconnecting the tan wire in trunk and leaving it open does what? If the guage reading is the same with tan wire in trunk open or grounded the problem is closer to the console.

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post #3 of 10 (permalink) Old Sep 27th, 09, 05:21 PM
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Re: Gas Gauge or Sending Unit?

This sticky https://www.camaros.net/forums/showthread.php?t=73968 from the electrical basics thread which is stuck at the top of the electrical forum, covers the fuel gauge circuit.





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post #4 of 10 (permalink) Old Sep 27th, 09, 08:57 PM Thread Starter
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Re: Gas Gauge or Sending Unit?

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Originally Posted by yellow69RS View Post
Disconnecting the tan wire in trunk and leaving it open does what? If the guage reading is the same with tan wire in trunk open or grounded the problem is closer to the console.

Jeff


Disconnecting the ground, tan wire, wire on sending unit, etc. doesn't change the gauge reading any. Reads above full once key is switched on. I have full power to console gauges, lights work, temp guage works, etc.
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post #5 of 10 (permalink) Old Sep 28th, 09, 03:11 AM
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Re: Gas Gauge or Sending Unit?

With the key off, did the gauge always go back to empty?
If it did, flick the gauge with your finger or smack it with a screwdriver handle.
If you read ohms from the disconnected gauge tan wire, or in the trunk, to ground, do you ohms and how many? 90 ohms = full, 45 = half tank, 22 = 1/4 tank, all approximate.

You might get a potentiometer/rheostat from an electronics parts store, i.e., Radio Shack, of a range of 0-100 would be ideal, 0-500, 0-1000 ohms. Attach the center lead to the disconnected tan wire and the left lead to ground. You should be able to rotate the gauge through its range by turning the pot. If you can control the gauge, even from the tan wire sending unit, you can assume the wiring and gauge are good. sending unit needs attention.

An ohmmeter reading should be indicated when measuring the unit from its terminal to ground.

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post #6 of 10 (permalink) Old Sep 28th, 09, 06:47 AM
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Re: Gas Gauge or Sending Unit?

Quote:
Originally Posted by dale3in98 View Post
Disconnecting the ground, tan wire, wire on sending unit, etc. doesn't change the gauge reading any. Reads above full once key is switched on. I have full power to console gauges, lights work, temp guage works, etc.
OK from this information you have an open circuit someplace in front of the trunk. High resistance or Open cicrcuit makes gauge go past full. Somewhere by the Ebake is another connector, disconnect it there and then ground tan wire. If guage goes to empty then open is between there and trunk if gauge doesn't change then go to console connector and try there.

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post #7 of 10 (permalink) Old Sep 28th, 09, 07:43 PM Thread Starter
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Re: Gas Gauge or Sending Unit?

Clean the terminal on both sides on the sending unit...checked the ohm readings and the unit is working fine...however, corroded terminal could have been a problem...cleaned everything, before doing the reading. Friend came by and asked about power to the sending unit...duh...didn't check that. Turns out that the sending unit isn't getting power...loose connection on the plug for the console gauges. So, connection was probably the problem, but the terminals did need cleaning. I think I will install a new sending unit anyway now that I have this one out.

After reading some posts, I think I will go with the Premier sending unit...seems to have plenty of good reviews...unlike the OER stuff from other suppliers.

Thanks to all for information and helping with the problem.
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post #8 of 10 (permalink) Old Oct 3rd, 09, 03:10 PM Thread Starter
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Re: Gas Gauge or Sending Unit?

Still having gas gauge issue...now the hand want move off Empty. I put a new sending unit in...same thing...put the old one in same thing. I think I am getting a ground from somewhere. I have power to the rear harness tan wire until I plug the sending unit into the harness..then nothing. Both sending units and gas gauge appears to work fine untill I put the sending unit in the tank. I have the ground hooked to the factory location on the trunk floor. Something is throwing a ground...just don't know what.


Any thoughts or suggestions?
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post #9 of 10 (permalink) Old Oct 3rd, 09, 03:44 PM
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Re: Gas Gauge or Sending Unit?

Judging from your replies, you didn't read the troubleshooting guide I linked either.





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post #10 of 10 (permalink) Old Oct 4th, 09, 07:46 AM Thread Starter
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Re: Gas Gauge or Sending Unit?

Quote:
Originally Posted by JimM View Post
Judging from your replies, you didn't read the troubleshooting guide I linked either.


Yes, I read the guide and it along with other threads were very helpful...thanks. The latest issue was just a "not thinking" moment...I forgot that the sending unit doesn't have power when showing empty...the power supply is opened once the float moves up. Just one of those DUH...moments.

Thanks again for all the help and info.
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