how do i tell if the alternator is working
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1990 Ford Mustang GT Question: alternator problems
Answer #1mastertech6371 November 12, 2010, 20:42Master
put a voltmeter on the battery with the motor running. it should be between 13.7 and 14.5 volts. any lower and you may have a failure.
Answer #2wrenched November 12, 2010, 21:04Technician
On most cars all you have to do is unhook the positive side of the battery when the car is running. If it dies the alternator is not working. If it is not working your battery will just run out of juice, no light, no start.
Answer #3Machinehead6 November 12, 2010, 22:22Enthusiast
Check the voltage at the battery, you can do it with the lights on to see if it holds under load.
DO NOT REMOVE THE CABLES WHILE THE ENGINE IS RUNNING!
This worked on older cars but ones with computers are sensitive to voltage spikes wich you will get if you remove a cable while its running.