Hello Forum.
I have 1993 240 Station wagon.
Battery voltage drop down after long drive on the freeway and can't crank up the starter when stop for gas or shopping. Voltage down to 12.1 or something Lo.
Usual everyday use for in-town or 45 minutes drive are totally non problem. But this happens only when I go on long distance drive(more than one hour).

Batter is about 2 years from new. Clean terminal and good grounding.
Alternator, replaced voltage regulator with new brush about a year ago.
Belt is good, about a year.

I tested by my batter tester and also multi meter, not showing any bad result for both Alternator and battery. Also today, I asked Advanced auto shop to test by their expensive testing machine, was not showing any problem.

Anyone help me out this?
Have a nice day!
Thank you!

 

After you get home for a long drive, leave the engine running and check the voltage. Perhaps there is something that is failing after it gets good and warm.

 

so when you tested the alternator, you did this in the car, by verifying that the battery voltage was around 13.8-14.2V when the engine was running?