Double Yikes ! I put a newly rebuilt, correct numbers, beautiful case, labled diodes alternator into my 340 hp swc yesterday. It started and I ran it for a while, checked the voltage at 14.8, I assumed that it was charging fine. Went to start today- not a thing except dim lights, not even the click,click,click-NADA.
Put the old alt. back on, tried again-nada.
Tried my battery buddy and it tried to turn over-hmm
Put the charger on it and it registered zero on the charge.
Volt meter still says 12 w/o load, turn the lights on-drops to 1 volt
The charger has been on for hours w/o a budge.

Can assume that the new alternator did this by draining through a short or could it just be coincidence (unsure of the battery life)
The old alt was 32 amps, new has 37-any effect?

 

I would pull the alt and bring it to a local Auto electric shop and have it tested. If it checks out, may be time for a new battery.

 

I think its time to replace the battery. If it is registering 0 with the charger on then it isn't taking a charge and most likely the plates are sulfated up to the point where it can't be charged. It can happen very suddenly, be fine one day and dead the next.

 

It is battery time. Your alternator swap was likely just coincidental. I would recommend that you have the new battery load banked (with you observing the test!) before leaving the store with your new purchase. I recently bought, then installed a brand-new battery in my '66; it turned out to be faulty & wouldn't start the car when engine compartmeent got hot after a run. So ... got to do all that again. Even though it was a parts $$ wash, changing battery is not "fun".

 

Today I bought an Optima 75/35 today. The old battery load tested to nothing. Used the opportunity to clean and buff expansion clamps and hardware. Started right up, running at 14.3 volts, when I turned the lights on (while running)the voltage actually went up over 15 -is this normal?
With the car not running, the battery scored about 12.5, lights on when not running-rated 12.5 and steadily dropped. Normal I guess?
The old alternator is back on until I get it to my electrical guy, then I hope he can diagnose any other issues/problems.
Thanks to all for the guidance.