We're on our third alternator
and none of them seem to charge.
About a week after we bought the boat
in 2015, a 1990 Catalina
42, we had to replace all of the batteries
as well as the charger
. We also replaced the alternator
which didn't appear to be charging
. Since we typically weren't cruising for longer than a week, shore power
was adequate to re-charge the batteries
and so I didn't realize there was still a problem.
Last summer, the batteries died while we were cruising in the San Juans. Voltage at the batteries and at the alt did not increase with the engine
running at any RPM
. Not having time to properly diagnose the problem, we replaced the alternator again at Roche Harbor, with no success.
Last week, I had our second alternator bench tested (we still have it) and it passed.
I checked voltage again and here are the readings that I get:
Off Engine On
@Batteries 12.66 12.42 (Idle)
@Batteries 12.66 12.36 (2K)
@Alt 12.43 12.25 (Idle)
@Alt 12.43 12.24 (2K)
I also get voltage at the R terminal, over 12 volts. I'm unsure of the role that the L terminal plays; based on my reading, it seems to depend on the application. Even the breakout diagram in the engine compartment shows that the blue and black wire goes to the tach. But when I disconnect the R-L terminal, the tach still works, so I think the sensor must be at the crank.
I guess I could try swapping # 2 back in... What else can I test for?