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traub 04-27-2008 04:31 PM

Jumping Tac
87 325i - 148,000 miles - Automatic - Runs fine, but the tac jumps up and down. It will just sit there at zero, then jump up to 2,000 rpm or what ever speed I'm going, then a second later, it drops down to zero again. Sometimes it works for a while... say 15 20 minutes. It acts like it's just losing power intermittently? Before I go pulling the dash apart to pull the cluster, it would be nice to hear if somebody else has had the same problem.

Yurick 04-28-2008 05:44 AM

Sounds like you need to change batteries in your SI board.

traub 04-28-2008 09:05 AM

Thanks... but I plead ignorance.....SI? as in the circuit board on the back of the instrument cluster?

Yurick 04-28-2008 11:28 AM


alpine325 04-29-2008 12:49 AM

UH I would say its a loose connection in the cluster. All you have to do is tap the on the cluster if it jumps then its a loose connection. But it also could be a bad tachometer. Question are the lights on for oil/inspection? If so get them reset if they come back on then the si batteries are bad if not then its just a loose connection.

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