Hello fellow Trans Sporters!

We have recently acquired our second 3.1 Pontiac ('91) and, beside the temperature gauge starting from 1/4 up there's another very interesting electrical issue:

- if you take the battery + cable off with the motor running the motor shuts down immediately

On our '92 Pontiac TS with the same 3.1 engine the motor keeps running when I took the + cable off.

Does anybody knows why this happens? Any idea would be greatly appreciated.

....if you take the battery + cable off with the motor running the motor shuts down immediately.

I would not risk that. The battery is an efficient voltage damper and even with a voltage regulator in the alternator, a voltage spike at battery disconnect is highly possible and it has happened that it blew one or several electronics components. I've seen it again at a friend's place last summer.

THe way different regulators behave might explain what you describe...in addition, rectified voltage from the alternator is supplied by a series of voltage pulses that can turn off to zero in between and the alternator looses excitation..and this can depend on the number and type of accessories in operation .