Car dies but battery, altenator, starter, parasitic drain, etc test fine

Maintenance/Repairs
41

Any chance the belt is not getting a good bite on the alternator pulley? You could try placing a boxed end wrench or socket on the alternator pulley and then try to turn it.
The pulley should not turn at all or it should be very difficult to turn.

The random dying at lights could be the system voltage dropping too low. In the old days one could drive a car across 2 states without lights on the battery alone and down to 5 or 6 volts.
Get them down to 10.5 or so anymore and they will quit.

42

Ask your shop to temporarily install a volt meter the driver can monitor as the car is driven. The voltage should normally be in the 13.5 to 15 volt range when the engine is running, and always read over 13 volts when the engine is running.

43

You can buy one of those plug in readers for $10 or so. Will tell both static voltage and voltage while running.