Random no start / Battery drain
 

I have been having an issue with my '83 944. ...about 50% of the time it won't fire up and the battery dies quickly (like in 3 attempts). It doesn't matter if it is wet or dry, cold or hot (weather) or if the car is cold or hot. The starter and battery are new (replaced by PO).Got any suggestions ?

does it crank strong? take the battery out and get it tested at autozone.

every time a battery get drained dead, it loses like 50% of its capacity.

once the car is running, is the alternator putting out enough voltage and amps? get that tested that too.

Alternator is putting out 13.8 volts when car is running. The starter cranks strong, but not as strong as when getting a jump.

.....as much as i hate to say it....sounds like a bad battery. :P

+1 on the bad battery. It's weak which is why it drains so fast.

I would look for a parasidic draw on your battery before you replace it again.
Take the key out of your ignition
Open hood and take out light
Disconnect POS battery terminal
Place a meter between battery lead and Pos post
It should not exceed 65ma some will say 50ma so somewhere inbetween.

If you find an excessive draw get someone else to help full fuses and relays 1 at a time until draw goes under spec. That will isolate the circuit then you have some work to do from there to fix..