ack - tach signal noise? (no tachometer / no speedo)
 

I just don't get it. The tach moves up only when jumpered to a sqr wave signal generator. (and does so with less voltage than otherwise present - same for speedo)

The voltage of the car seems good (13.8 - 14.1 running).

Swapped in a spare CD - nothing

Getting 4.xx volts at the signal (black and purple) wire. ...jumpered directly to the CD signal plug just to test. - still nothing.

Grounds jumpered...

All I can figure, at this point, is that there is maybe some extraneous electrical noise pulsing thru the system.

Any ideas out there? Do voltage reg's get noisy?