Originally posted by: robphelan
the old method of testing the alternator was to disconnect the neg terminal of the battery while the care is running. If it dies, the alt is the problem.
This holds true for Generators,not alternators.
Originally posted by: robphelan
the old method of testing the alternator was to disconnect the neg terminal of the battery while the care is running. If it dies, the alt is the problem.
Originally posted by: homercles337
Originally posted by: robphelan
the old method of testing the alternator was to disconnect the neg terminal of the battery while the care is running. If it dies, the alt is the problem.
Exaclty what i was going to say. Just make sure the car hasnt been runnign for a while. Some batteries are just weak, but will take some charge. So, just jump it, then disconnect the battery immediately.
[edit] meant battery ... [/edit]
Originally posted by: FrustratedUser
Is the OP listening?
Originally posted by: Rumpltzer
To be a little more clear... you have a 12V battery in your car. If you disconnect the battery and measure the voltage, it might read something like 11.5V.Originally posted by: Heisenberg
Put a DMM on the battery while it's running and see what the voltage is.
If you turn on the engine, the alternator will charge the battery and you'll read something higher... maybe 14V. If the alternator is dead, you won't read "something higher".
An alternator is not the same thing as a generator; it will not turn into a motor when the rectifier diodes fail. The diodes are simply to convert the AC the alternator produces into DC to charge the battery.Originally posted by: Scarpozzi
What year is the car? Have you ever changed your battery? Usually batteries have 5 year warranties on them. You can expect a battery to last at least that long....some will last 3-4 years....it's a mixed bag.
AZ will check your battery. The alternator can't charge a bad battery.
If the alternator goes bad, it will sometimes draw current from the battery even when the car is off... (bad diode can make the alternator (generator) turn into a motor) So start with the battery and don't listen to any mechanics trying to talk you into replacing the alternator yet.....
Originally posted by: Eli
An alternator is not the same thing as a generator; it will not turn into a motor when the rectifier diodes fail. The diodes are simply to convert the AC the alternator produces into DC to charge the battery.Originally posted by: Scarpozzi
What year is the car? Have you ever changed your battery? Usually batteries have 5 year warranties on them. You can expect a battery to last at least that long....some will last 3-4 years....it's a mixed bag.
AZ will check your battery. The alternator can't charge a bad battery.
If the alternator goes bad, it will sometimes draw current from the battery even when the car is off... (bad diode can make the alternator (generator) turn into a motor) So start with the battery and don't listen to any mechanics trying to talk you into replacing the alternator yet.....
Hey guys, I Have a Mk4 Gti I have a Similar Problem to this. My car would be completely dead but after I jump it it will turn on, crank, start, & Run.... it doesn’t cut off actually if I turn it off I can start it back up again after a while then it’ll eventually die again & need a jump
Take out the battery and take it to AutoZone.
If not battery,
Take out the alternator and take it to AutoZone.