My 1991 Ford Tempo is having electrical problems AGAIN!
You may recall that a year ago my alternator was diagnosed as dead by my mechanic. Thanks to the help and encouragement of several Dopers, I replaced it with a used (but NOT rebuilt) alternator myself, thereby saving mucho buckos.
Well, once again, there’s trouble in Tempoville tonight. Yesterday, out of the blue, the dashboard “AMP” (w/ battery icon) warning light began to glow pretty steady. Minutes later, all the elecrtical functions in the car started to dim and die; I just barely made it to my parking spot.
I found the battery terminals horribly salt-encrusted, so I cleaned them bright, thinking that was the trouble. No such luck. The AMP light still kicked on after a few minutes of revving.
Okay, maybe the battery is just shot, I thought. I took it out of the car and had it tested at Pep Boys. The battery tested good. And the AMP light is still on.
So now I’m thinking it’s another dead alternator – but I can’t really be sure, right?
How can I test my alternator, preferably while it’s still in the car?
If I recall correctly, there are 4 wires coming out of the alternator: One big, thick one that is held in place with a nut (covered by a rubber boot), two that snap into the housing via a 2-wire plastic connector, and one that snaps into the housing via a 1-wire plastic connector.
A fast search of the internet tells me that the olde school test method of disconnecting the battery while the car is running (“if car dies, then alternator is bad”) is dangerous and unreliable.
The AMP warning light goes out when I rev the car really fast (in neutral) but it does not stay out long. (One internet source said that may be because of residual magnetism in the stator making an otherwise-dead alternator look like it’s working – but I may have read the details wrong.)
I have no real test equipment to speak of. I can rig a 12V test light with an extra car bulb; I also have an “autoranging pocket multimeter,” but I don’t really know how to use it. (It was a well-intentioned gift.)
Thanks all, in advance.