Dear friends, this is a real puzzle.
The car:
Volvo 940 2.3i estate (1995), 210k mi. Regularly serviced.
The problem:
Twice now, the car has discharged its battery completely inside one minute, only to be rendered fine again with a jump start.
Instance 1 happened in seriously heavy rain round a roundabout which made me think it must be water and electricity not making friends.
Instance 2 dashes this theory as it was a beautifully warm day, car used 4x before the fault. Sat to listen to radio for fewer than 5 mins (no rain, engine not running) and it was dead to the point the radio reset itself etc. A jump and it was fine.
Battery reads great voltages cold and running but whenever this problem surfaces, the car won't even click the starter solenoid it is that weak.
I wondered if it was a loose earth so have been throwing it over speed bumps and round roundabouts and sharp corners to see if I can replicate the fault with cruel treatment; I can;t.
There seems no commonality in instances where the car chooses to fall over.
Fuel gauge only worls 2% of the time. Fresh plugs and bougicord leads fewer than 10k mi ago.
https://www.volvoforums.org.uk/showthread.php?t=313229
The above thread is realy insightful and details the tracking of a similar electricity demon.
I love this car and don't want to hear 'scrap it'. Any advice really appreciated. Stuff I've ruled out is fuel as it has happened once with the engine running, once with it just providing power to radio. Battery itself - this is healthy.
Cheers,
F