I’m looking for some advice on an odd alternator tach issue: I’m not getting a clean signal, and the signal is showing a _much_ higher RPM than expected.

This is on a Balmar 12-pole 12v alternator which recently had a new diode bridge and regulator installed. It otherwise appears to work correctly – I’m getting good output in terms of current and voltage. But the tach signal jumps around and is registering at ~10x the expected rpms. I’m suspicious of the wiring, but unsure what could cause a bad tach signal when the alternator otherwise acts normally.

Are there any internal or external wiring issues that you’ve seen that could muck up the tach signal? And advice on how to dig into this would be very appreciated.