To test your alternator, you unplug your negative battery terminal, right?

chriswf · August 14th, 2009, 4:29 am

Fixed my horn, since my regular battery was dead, I threw my giant red top in the engine bay. Plugged it up.

Drove around for about an hour, and the voltage stayed about the same. But those red top batteries can go forever!

So I came back home. Pulled off the negative battery terminal while the car was running, and it shut off...

Was I supposed to pull the positive? I forgot what the trick was...

It started back up... It was having a problem charging before. Not sure if it still is or not. I have work tomorrow. It'll probably make it to work tomorrow, and maybe back. The problem is when I'll break down by surprise thinking it's okay. Or it won't start when I'm already running late one day...
Ya know?

Any other problems? Bad terminals on alternator?

probed_out · August 14th, 2009, 4:32 am

you can take off either wire i think or at least thats the way my old pickup is

never2fast · August 14th, 2009, 4:47 am

No you cant take eather cabel off to check the alt it will die turn you head lights heater and rear defroster on swatch the volt guge it will drop a litel and come back up if the aly is working.

probed_out · August 14th, 2009, 4:54 am

or get an battery/alternator tester

mattkane123 · August 14th, 2009, 10:34 am

yeah, im pretty sure any autozone will test any battery or alternator for free...
just go down to ur local parts store and ask them about their electric test policy.
some will even do it all for u.

SALEEN961 · August 14th, 2009, 10:42 am

If you go to Autozone for a free test make sure they enter in the correct value for the CCA's I've watched them enter values that are way off before just because they can't be bothered to look at the battery. If they enter the wrong value the test is useless and will tell you nothing.

Same holds true for alternator and starter testing, with these the test values are harder to locate and as such they are rarely correct.

alexm963 · August 14th, 2009, 8:02 pm

if you have a voltmeter just check the volts at the battery with the car running. It should read around 14 volts if the alt is good if not it will be around 12 or less.

monoxidechild · August 14th, 2009, 8:13 pm

^
thats all i do. i use a ohm meter. but anything along those lines will work. and doesnt involve any work. its harder to pull off the battery cable. lol

michaelknight · August 17th, 2009, 2:38 pm

13.5-14.4 is good