Tachometer

[morganbill]

When I turn the ignition key to on, the tachometer will cycle from 0 to max rpm and back about 10 times a minute whether the engine is running or not. Also the oil pressure gage is pegged high. Just wondering if this is as simple as a missing wire. The tach is run off the alternator and the engine is a Volvo-Penta diesel with a Volvo-Penta insturment panel.

Thanks for any insight.

Morgan Bill

[Valiente]

Originally Posted by morganbill

When I turn the ignition key to on, the tachometer will cycle from 0 to max rpm and back about 10 times a minute whether the engine is running or not. Also the oil pressure gage is pegged high. Just wondering if this is as simple as a missing wire. The tach is run off the alternator and the engine is a Volvo-Penta diesel with a Volvo-Penta insturment panel.

Thanks for any insight.

Morgan Bill

That could be a number of things, (intermittant short comes to mind) but if it's any guidance, when I turn on the blower on my glass fuse-protected Atomic 4 (when its running), the oil pressure meter drops 30 psi, the temp gauge goes up 10 degrees and then both snap back when I push the blower switch in.

I've learned not to freak out, rather than to actually trace the issue and fix it.

[resdog]

A poor ground will cause an electric tach to jump around.