When I am at a stop with lights on, the blinker blinks slow, the battery goes down to around 5 volts, and the tach and lights jump and dim to the beat of the slow blinker. I checked the battery while running in park with everything on and is 12.8 volts. The battery is good with the car off also. The car is set up so one fan is always on, and I have to crank it until the oil pressure switch starts it as the fuel pump won't prime. I don't know if those things are related. Any help would be appreciated.

I'd take the alt. off and take to autozone and have them test it for free. it may not be your problem but you can cross it off your list atleast. when it was in park did you have everything else on lights,blinker,fan,ect,ect.

I will do that, when I tested it I had everything on except the wipers. The alternator looks new but still could be junk. It seems strange that 250 rpm would make a difference between idling in drive and having the car in park. No autozone here, does another chain do that for free?

O'Reilly Auto Parts checked mine out and i had a bad one. Advance checked the same alternator and said it was good. I would try an O'Reilly's if you have one.

I'm having the same problem and have had 2 alternator's checked. I went ahead and bought one thinking mine was bad and then had it checked, it was still good. Now i have a spare if i need it. But, i'm still having the same issues your having. Haven't had much time lately to work on mine though.

what rpm were you turning with the foot on the brake and did it seem like the car wanted to die. may be a vacuum leak in the brake line. but that's probably unlikely.

I had (still have, but the car is in a thousand pieces at the moment) the same problem. I got a new alternator, new battery, new positive battery cable, did some wire fixing, cleaned the ground wires, etc and still didn't find the problem.

I believe I may have found the problem when I was removing the engine. When I took the wire going from the distributor to the thing that ups the amperage/voltage (for lack of knowing the real name) off of the distributor, dust went everywhere. There was a lot of corrosion in the wire and on the terminal. After removing everything electrical related from the car, that is the best I have come up with.

I recommend you check on that and see if it helps.

when we get out of single digit temps (Saturday) here I will do all of the suggestions and see if I can get it figured out, thanks