Before replacing the alternator, make sure the battery is not the problem. Your local auto parts store can test and charge the battery.

 

Wouldn't it not start if the battery was bad?

 

also if there is an autozone they can check your alternator on car. you just have to ask them. it only takes them a second it will also tell you how many amps its running at. they can run at about 60 percent without causing a problem my truck runs at 25 amps on an 80 amp alternator and it has a whole bunch of lights on it 4 kc lights and a couple extra interior lights. other stores might be able to but i know autozone does for sure.

 

OK. I charged my battery and when the car is at idle it still reads roughly 12V. I tested the ground on the battery and the alt and they're both fine. I hooked another fully charged bat up to the one in the car and the problem still occurs. I also checked the belt tension on the alt and it only moves about a centimeter. I did find 2 burnt out fuses; one for the rad fan and one for the radio, looks unrelated to the problem but i wouldn't know. Its snowing here so i cant go out to get replacements.
To recap; the car dies when the breaks or headlights are turned on.
I'm pretty convinced its a bum alternator but i would like to know for sure before i spend 200 on a rebuilt one. and it looks like a pain to get in there.

 

if you are using a multimeter then throw it into amps mode and toss the hooks around your negative cable coming off the battery and it should read approximtly the amount of amps your alternater is supposed to run at. if its only 10 low then its probably not it. how long will it sit at idle with everything off?

 

It'll stay at idle. I ran it for a half hour to see if things would change when its warm but the problem was still there. But I can run the climate fan on max and it doesn't have affect. Oh and the ECU isn't showing any codes.

 

Inspect fuse 31 (60A) in the main fuse box. This fuse protects circuits for the brake lights, head lights, and the main relay/fuel pump, and others. I assume that insufficient amperage is available for for all of these circuits, causing the fuel pump to shut off. Therefore, also thoroughly clean the battery posts, connectors, and the engine bay ground wire with steel wool. As mentioned, also try to get the alternator tested.

 

All fuses in the main box test OK. Is it hard to remove the alt from this car?

 

Forgot to mention the temp and gas gauge don't seem to work too well. Either the gas gauge works or the temp works but never at the same time.

 

Problem solved. Would you believe a bad ground in the tail light could do all that? 2 cranks on a loose nut and everything works now.