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A blown fuse was causing my gauges not to work, but now they all work fine one I replaced it... except for the tach. When I turn the key to the ON spot, it goes to about 1,000 rpm, then as I crank it to start, it spins all the way around, stops at 0 and doesn't move while running. Any ideas? :dontknow:
 

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The tach only needs 3 connections --- 12 volts, ground, and the wire from the distributor. These 3 signals are all on the printed circuit that runs on the back of the gauge cluster. You might have a bad connection there.

Since the needle swings when you turn the key on we can assume it has 12 volts and a ground. The ground may not be very good, though. That pretty much leaves the distributor signal.

If you have a voltmeter (multimeter, DVM, etc.) disconnect the tach wire from the distributor and connect the voltmeter to the dist. Set it on about the 20 volt scale. Start the engine and see if the voltage changes as you rev the engine. Try both the DC volts and the AC volts settings on the meter. If you have good voltage readings the the dist is OK. If not, it might be bad. Hard to definitely say since it might not "like" your voltmeter.

Now for the real question. Why did the fuse blow? Do you have any idea what might have caused it? Were you doing something that might have shorted some wires? Were you messing with the wiring under the hood or under the dash?

You MIGHT have hurt the module in the distributor.

Sorry I can't do better. It's hard to diagnose w/o checking the printed circuit.

Jack
 
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