how do I know my Alternator is bad?

Belto said:

my bat gauge is never at 14 its about 13.6 something like that,, and when I turn the AC on it goes down to nearly 10 then when I accelerate it goes to about 12... a friend says my alt is bad. since my bat is new

is this normal for the xj or should I check my alt?

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Could be, it also could be how tight your belt is, or even corrosion on the battery cables.

I'd do the cheap simple stuff first. Clean battery posts. Replace battery cables. Tighten the belt.

Wal-mart sells a battery charger that will tell you how well your alternator is working. Might be worth the investment of $35.

well my bat cables are pretty ugly

also a friend suggested to get a ground wire kit... that that will help to destribute the energy better

Just clean all connections and make sure they are firmly connected. If that fails go to your local parts store, they usually test alts for free.

all conections are good, Ive had this since I bought it,, but now Im concern bc my friend scared me ,,, LOL, im uploading pics of the cables now... so you guys can see

Just because the were good doesnt mean they still are, I would go through and check them all. Trust me the same thing happened to me.

BTW when I talk about connections in mean the connections direction to your alt.

Kyle said:

Just clean all connections and make sure they are firmly connected. If that fails go to your local parts store, they usually test alts for free.

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Do they check the alternator while it is still installed, or do you have to remove it?

I've only had mine tested after I removed it.

Mudderoy said:

Do they check the alternator while it is still installed, or do you have to remove it?

I've only had mine tested after I removed it.

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They test it while removed, but removing an alt isnt a bad job at all.

well I just installed a ground kit,, the bat gauge is still the same at idle with the ac off, but when I turn the AC on it goes down like always but it comes back up agian pretty quickly but its never at 14 its just a lil to the left of it..

I will go later to check the alternator at the local autoparts.. but not today...

i used a multi-meter at school after i fried my alt. left the alt in the jeep and it could tell just by being connected to the batt if the alt was bad. when my alt was bad though, it just went to flat 9 no matter what. wouldnt change.

Isn't there a trick where you can disconnect the battery while the jeep is running and if it stays on, the alternator is fine, if it shuts down, it's bad? I heard about this a couple years ago. I dunno how that would work on modern cars with all the electrical crap.

muddeprived said:

Isn't there a trick where you can disconnect the battery while the jeep is running and if it stays on, the alternator is fine, if it shuts down, it's bad? I heard about this a couple years ago. I dunno how that would work on modern cars with all the electrical crap.

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I hear this can damage the computer. The battery acts as a big ol' AC filter.

But you are right, disconnecting the battery while it is running would tell you if the alternator is producing enough electricity to run the engine.

yeah disconnecting does work. I just did this with my gf's car(saturn) kept dieing pulled ground stayed runnin, put ground back on pulled positive kept runnin. Took the battery in and it was bad.

Same thing happened yesterday, wouldn't start. Disconnected battery shut right off. Putting a new alt on tommorow i will let you know if that takes care of it.

new alternator worked!! the postive connection on the alt was broke the whole stud was moving. Had to cut the wire. Cuz i couldnt get the nut off.

so your going to make a howto on swaping alts?^^^


BC I went to check mine, and its bad, when I turn on the AC it gets lower than 12.3 alt, and the guys said that it should never come down from 12.6 alt also when lights and ac are off it does not go to 14alt the guy said that as long as I dont use the AC and use a lil as posible the lights,, I wont have any trouble..

Another problem solved by....

CherokeeTalk.com!!!

:thumbsup:

you want a write up on how to change an alternator in a 95 saturn? lol (it was a mother) i had to pull the inner fender and p.s. pump

kmanxj5050 said:

you want a write up on how to change an alternator in a 95 saturn? lol (it was a mother) i had to pull the inner fender and p.s. pump

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Sorry dude, you're looking for SaturnTalk.com