Gas Gauge Problem
Short answer: The gauge swinging to empty when you switch on the lights is the classic bad-ground symptom. Check the grounds first: one is at the sender on the tank, the other near the filler neck (a large sheet-metal screw into the trunk floor). Quick test — run a jumper from a known good ground and touch the metal gauge-cluster housing; if the trouble clears, it’s the ground.
If the ground is good, suspect the sender. It’s a rheostat (resistance wire) with a float-driven wiper; over the years the windings wear, shift, and develop dead spots — giving no reading or erratic readings, eventually failing. GM used a 0–99 ohm range (mid-scale ≈ half tank). Test with a meter on ohms; if worn, replace it rather than repair.
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Content last modified: June 13, 2026 at 10:06 am
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Need some help, I replaced my sending unit the gauge only should a half of a tank before I replaced the sending unit when it was full, So I replaced the sending unit after draining the tank and installed the new unit I had checked the gauge knowing that the tank was empty The gauge was reading a half below the empty mark, I then poured in 6 gallons and it now reads a 1/4 below empty, I have checked and the ground is hooked up, Any thoughts?
THanks