81 fuel gage

[mrrecon4]

I am loosing my mind I have put in a new sending unit and gage, check the ground by the tail light(Is there another one i don't know about) but no matter what i do the gage only works the top half of the tank in another words when the tank is full the gage reads full but when the tank is half empty the gage reads empty and goes down accordingly in between full and half empty any help would be great. Thanks in advance

 

[TimAT]

IIRC, GM's gauges are 90 ohm sending units. Maybe the wrong sender? Or really badly bent float arm? Just for giggles, pull the sender wire off the sender at the tank, hook a 12v testlight between the wire and a good ground and turn the key on. See what the gauge does. It should go to about 1/2 scale. If it does, add another testlight, that should drop it by 1/2 again.

 

[bagger]

You say you changed out the gauge with a new one. Not sure if the 81 is the same as 68 but when I changed out mine, there was a small resistor on the back of the gauge that bolted on the 2 poles on back of the gauge. I put the new gauge back in with the resistor in place and my gauge read way off like yours. I found out that the new gauges have the resistor built into them already and don't need the old factory one. I took the gauge back out, took off the resistor and put it back together and the gauge worked like it was suppose to. Hope this helps you. Good luck.

 

[mrrecon4]

IIRC, GM's gauges are 90 ohm sending units. Maybe the wrong sender? Or really badly bent float arm? Just for giggles, pull the sender wire off the sender at the tank, hook a 12v testlight between the wire and a good ground and turn the key on. See what the gauge does. It should go to about 1/2 scale. If it does, add another testlight, that should drop it by 1/2 again.

I tried your idea when I pulled the sender wire off it went stright pass full i then hook up the test light and it did not move, I checked the ground it is good and i am getting a reading on the testlight so is it a wire problem or possible the circut panel behind the gages thanks for the help

 

[TimAT]

With the testlight in the circuit in place of the sender, the testlight shuld "glow" not real bright, but enough to see it, and the gauge should go about 1/2 scale. Disconnecting the sender the gauge should go full scale full. If you ground the wire to the sender, the gauge should go full scale empty. If that does not happen, then you have a problem with the gauge or the board. The little resistor behind the gauge might have died.

 

[mrrecon4]

is the little resitor the plastic piece on the back of the guage, where can i get one?

 

[yello80vette]

As simple as the Needle?

Are you sure when you were working on it, you didn't pull the needle off and then reinstall it in the wrong place?
Or maybe just bump it and move it?

 

[BankOfHell]

Sometime when gauges sit awhile they act kinda funky. Try ccyling the gauge by hooking and unhooking the connector when near empty.

 

[mrrecon4]

Are you sure when you were working on it, you didn't pull the needle off and then reinstall it in the wrong place?
Or maybe just bump it and move it?

i mit have bump it but this is the second gage with the exzact same problem

 

[mrrecon4]

Sometime when gauges sit awhile they act kinda funky. Try ccyling the gauge by hooking and unhooking the connector when near empty.

without relizing it i have been cyling it while working on it with no change

 

[bagger]

Not sure where you can find the old style resistors. Since I put new gauges in I put the old resistors back on my old gauges when I stored them. You might be able to find them at the various gauge rebuilding shops. Roger's helped me with my problem.

Index

Here is the place that helped me solve my gauge problem. Hope this helps. Good luck.

 

[bagger]

Sorry about that Index

 

[bagger]

Sorry again. Click on the "index" that will bring you to the website.

Indexhttp://www.corvetteclocks.com

 

[mrrecon4]

here's the latest I tried all the tricks you guys suggested and i thought the gage started working which would mean bad connection or wire, but when i filled it up today it went way past full like when you disconect the sender. I will drive it around a while and see what happens if the guage works i might leave it alone i would rather the full side be off then not knowing when i am running out of gas. I will let you know how it turns out
thanks for all the help

 

[Peer81]

I had the same problem with my Mazda (sorry).
Turned out to be the sendingunit inside the tank. With the tank full it would give (high or low, don't remember, ohmage) and according to the fuel level in the tank the ohmage would go up (or down..) but at 3/4 empty the ohmage would drop to zero and the needle would go to empty (just when you need it the most). Fixed the problem by putting in another tank unit with float, sending unit etc etc. I hope it helps.

Greetings Peter

 

[BankOfHell]

I wonder if the new sending unit had some coating on the reostat windings to prevent corrosion or somesuch during package etc. I'd pull it one more time and hit the reostat windings gently with copper wool.