Originally Posted by
martysmartie
I said above, you need to check the charging system, the output might not be good under load, thus the battery discharges.
It's just a tacky thing to do and won't tell you anything, you can end up with voltage spikes etc, when can fry delicate ECU'S etc.
Martin
^^ yeh as said disconnecting the leads while running will create an open circuit which can cause any relays to not function or worse, when testing the alternator turn all lights on and heating so its under load