80' Gas Gauge Problem...
Thread Starter
Racer
Joined: May 2004
Posts: 315
Likes: 0
From: North Richland Hills TX
80' Gas Gauge Problem...
Awhile back ago my 80's gas gauge went nutz and fell completly sideways. Every once in a while it would read accurately, but then go nutz again! So, I swapped sending units w/ a rebuilt one and it still didn't fix the problem. Turns out, the rebuilt sending unit was bad, so I shelled out the extra $75 for a brand new one, but only to moderate success. Wen I fill up my tank completly my gas gauge only goes 1/2 way up now. So the guy who works on my car w/ me thinks we've narrowed it down to the console gauge circuit. I was just wondering if anybody has any other ideas what could be wrong with it, cuzz I'd hate to spend $100 on something that doesn't work out...
Le Mans Master
Joined: Mar 2004
Posts: 7,470
Likes: 1,490
From: Little Rock AR
The gas gauge sender is a variable resistance. Positive battery voltage is sent to the gauge and the ground for it is through the sending unit. You can check the wiring circuit by grounding out the harness wire going back to the sender near the tank. If you can ground the wire going to the sender with the key on, the gauge should indicate empty. If you disconnect the wire to the sender, the gauge should read over full. If this is not happening, you have a problem in the harness or gauge.
If you connect an Ohm meter across the sender wire (on the tank side of the harness) and the chassis ground, it should read zero Ohms with an empty tank, maybe 45 Ohms with a half tank and maybe 90 Ohms with a full tank. If you have infinite resistance, the sender is bad or the ground wire for the sender is not making a good connection.
Hope this helps.
-Mark.
If you connect an Ohm meter across the sender wire (on the tank side of the harness) and the chassis ground, it should read zero Ohms with an empty tank, maybe 45 Ohms with a half tank and maybe 90 Ohms with a full tank. If you have infinite resistance, the sender is bad or the ground wire for the sender is not making a good connection.
Hope this helps.
-Mark.
