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jbell959 jbell959 is online now
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Join Date: Oct 2004
Location: S California
Posts: 8,003
Quote:
Originally Posted by markyc100 View Post
Whereabouts is the driver board located ?

Is it likely to be this as opposed to a faulty tach?

hanks for the help
The driver board is inside the tach. It needs to come apart to diagnose the issue.

Quote:
Originally Posted by markyc100 View Post
I have connected a volt meter to the black and purple wire at the back of the tach.

Ignition on its reading 12.4v

Once started it drops to 10.8v and drops as the revs increase.

I am not very technically minded so would be grateful of any input as to how it all works and any help to resolving the issue.
Connecting a voltmeter to the purple/black wire doesn't tell you anything. That is the tach signal, which is basically a square wave. You want to connect your voltmeter to the 12V and Ground wires to make sure your regulator is working and the voltage isn't spiking when you rev the engine.

These tachs will work fine up to 20V, so your issue is more likely a damaged driver board, which could happen as a result of a bad regulator, so you want to check that before you repair the tach and put it back in.
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Old 06-28-2025, 09:20 AM
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