1993 240 Wagon
240k

Twice in the last two months the alternator failed to generate a measurable charge when I started the car in the morning after sitting all night.

The battery voltage each time was 11.8 to 11.9 and the 4 warning lights in the instrument cluster did not light. That's a pretty sure sign I'm not getting a charge.

On both occasions, I pulled the D+ wire at the alternator and connected it to ground to be sure that wire was ok - and it is. The 4 warning lights illuminated.

After letting the car sit for a few hours, the alternator began charging when the engine was started.

The alternator ground and B+ wires were upgraded about a year ago to solve a voltage drop problem. Everything has been a dream up until now. I documented this in a previous link here:

https://www.brickboard.com/RWD/volvo/1683069/220/240/260/280/new_60a_fuse_setup_93_240_ignition_circuit.html

What further steps can I take to pinpoint the issue? I really don't want to throw parts at it without understanding what is causing the issue.

Thanks.