Anyone know about debugging a flaky tach?

[Paul L]

My tach has started reading about 2500 when I turn the ignition on and the engine is off. I checked the ground and the other wires look fine. The other gauges are reading fine. When I start the engine the tach then pegs to full. How do I narrow done the problem between the wiring and the tach itself? This is standard Volvo tach on a 2003.

[Alan Wheeler]

I presume yopu checked wiring at both ends, Gauge and sender device. Sounds like a dirty connection to me. If you have checked the wiring bothe ends and all is OK, then it could be a cold solder joint inside the gauge.

[Paul L]

Yea, I've checked connections at both ends. They look good. I checked the input sense wire to the tach (W) and it seems like it has a plus 1.2 volts on it. I don't know if this is a good thing or not. So you think it is internal to the tach?

Paul