Phantom Gas Gauge

[blck325is]

After I swapped an I head into my eta I also switched over the odometer from the donor car over to the eta. The gas gauge worked fine in the donor car but when I switched it over 3 things happened, the rpm gauge, mpg gauge and fuel gauge stopped working. The fuel gauge started working but would show the tank as empty when it reaches the halfway mark. The other two are still completely dead. I intend to replace the entire cluster as some point but I'm just wondering why they don't work or what could have caused it.

[mr.vang]

i can tell you one thing, e30 gauge suck! my fuel,rpm gauge jump and get stuck all the time. i don't mind though cause i'm use to it. first thing i would do is check for any lose ground.

[jlevie]

If you are saying that the tank is empty when the gauge is indication 1/2, then I'd suspect that the donor car was a 9/87 or later 325i with the 63L tank. Those cars have two fuel level sensors and the gauge is calibrated for twice the resistance of your ETA with a 55L tank and single sensor.

[blck325is]

If you are saying that the tank is empty when the gauge is indication 1/2, then I'd suspect that the donor car was a 9/87 or later 325i with the 63L tank. Those cars have two fuel level sensors and the gauge is calibrated for twice the resistance of your ETA with a 55L tank and single sensor.

Hmm, so I should...do um what lol. I understand what you're saying and it makes sense but what do I do to change it. Also is that whats affecting the mpg gauge as well?

[jlevie]

If you have that problem the fix is to use a gas gauge meant for a car with the 55L tank (those built before 8/87).

The tach, mpg gauge, and temp gauge are dependent on the SI board. If all three of the fuses necessary for the cluster are good and the cluster ground (above the steering column) is good, replace the SI board.

[blck325is]

Ahh, I still have the old cluster so I'll handle that. Well I hope I have it anyway. Shouldn't be too bad to figure out what wrong with the other gauges now that I know what to look for. Thanks man.

[blck325is]

Installed the gas gauge from the old cluster and the same damn thing is still happening.. No idea what to do now, ideas anyone?

[jlevie]

Have you replaced the SI board with a known good one? Have you checked all three of the fuses that feed the cluster? Is the ground good?

[blck325is]

SI board will be getting replaced tomorrow, no idea which fuses to check but I'll find out. Gonna check the ground too. Really hope this works cause not having an accurate gauge, working odometer or working OBC kinda puts me in a tough place for knowing when to fill up.

[myfirst325]

Same thing just happened to my car. I drove it a mile to fuel up and the damn car wouldn't take fuel since apparently the tank was full but the guage was only reading half. I drove back home and noticed that the gas needed dropped to E and the odometer wasn't working any longer. I'm gonna do the same and check the ground and fuses. I was tinkering around under the dash removing the hood release cable and may have accidently moved something. Not sure how I'll fair tomorrow given that their's an aftermarket alarm tucked under the steering wheel column and it looks to have at leats 50 splices!