[GH85Carrera]

Originally Posted by Noah930

OK, here's a technical question:

I've had an intermittent problem with a bouncing tach. The car runs fine, but the tach will bop around like it's not connected to anything. I had the engine pulled in January to fix some oil leaks. When the motor was reinstalled, the problem resolved...for a few weeks. It won't do it all the time, just intermittently. As the battery was 7 years old, I replaced it. Problem went away...for a couple weeks more. Then it returned. The charging system (measured at the battery with motor running/revving) seems to be working fine, but those measurements were taken while the tach was working fine. Headlights/instrument lights work fine and are at their baseline barely luminescent H5 glow. I even swapped in a loaner tach, which also worked fine ... for a bit. I was going to drop my old tach off at North Hollywood Speedometer for repair when, on the way to work today, I just caught out of the corner of my eye an erratic tach bounce. Couldn't reproduce it for the rest of the drive, though.

So am I just kidding myself and do I need to swap out the alternator & voltage regulator?

edit: I'm sorry. Am I interrupting your regularly scheduled programming on chicks, beer, and guns with a technical issue?

Bouncing tach is usually a alternator problem. It was with my car. Pull the alternator and take it to a local alternator shop for a rebuild.