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Trying to install a small tach in an '89 245 DL.
The tach has 3 connections on the back (not counting the light)
One is obviously the ground. The other two have a long black wire, and a blue/red wire.
I found the red/white wire behind the dash, and hooked it up to the blue/red connector. Not sure what do do with the long black wire, so I left it hanging for now.
The tack seems to work, but at idle it's showing about 2000 rpm, and as I rev the engine the tack moves up, until it hits about 5k, then it drops down to about 3.5k, and then climbs back up to redline as I rev the engine.
Do I have a bad tach, or is this user error? Where should the various wires go?
Thanks.
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