Fuel Gauge Bad?

[Banana]

Troubleshooting  Rally Cluster gas gauge issue.

Tested the sending unit, check all grounds in the back, and the blue wire continuity from front to back. All seem OK.  Hooked everything up again and fuel gauge still at E (needle goes up a smidge when power on, but then stays on the E).

I then did the Cody test using the batteries (5V) directly to the back of the fuel gauge.  The needle starts to go up. At around 1/4 tank, the needle moves back towards E, then starts moving up again. Once it gets past 1/2 it slows down considerably, then really struggles towards 7/8 tank and never makes it to Full.

I would have expected the gauge to sweep smooth and quick up to Full with direct connection to the battery pack (the 3 batteries measured 4.91 Volts)

Anyone think I have a bad gauge (it's the original and has not been removed from the cluster)? Something else? Thanks

[Jay Bee]

Ground the blue wire, sit in the car, then turn the key to On or Accessory. The gauge should make a smooth steady climb to Full.

[JS29]

 

[Banana]

Thanks, did try that multiple times. The gauge acts quirky as I described in my initial post. So the gauge goes up to 7/8 herky-jerky slowly whether I ground the blue wire, or, put the 3 AAA batteries directly on the back of the gauge.

Do fuel gauges fail always catastrophically pegging to E? Or is there a partial fail as I described?

Thanks again

[Jay Bee]

FWIW, I never heard of the actual gauge failing but anything's possible. Do the oil and temperature gauges behave/act normally?

[Banana]

I also tried to test the gauge by directly connecting the sending unit to the gauge with the battery method (as shown in Cody's video). See if the blue wire was at fault. Unfortunately the sweep of the gauge needle was still messed up.

Based on all I'm reading on line, looks like sending unit, or grounding, are the issues 99% of the time.  Gauge failure seems very rare and easy to diagnose.

Waa hoping to avoid it, but looks like I'll pull the gauge cluster and do some more bench testing.