how do i know if the altenator is bad on a 1978 caprice classic?

Answer 1

On one this old you can do a simple check that you can't on newer ones. While running take off either the positive or negative terminal from the battery. If it keeps running it is find but if it dies, most likely it needs rebuilt or the regulator module in it replaced. If you take off the positive terminal make sure not to hold onto the metal (terminl) part as it will shock you if you touch the car anywhere else. On new models you can't do this kind of check as it will damage the computer.....YOu are safe to do it on this model car....

Answer 2

You can use the trick that other guy is talking about with unhooking the battery after starting the car, if it quites running then you have a bad alt. Just don't ever try this with a newer vehicle that has a computer in it as possible comp. damage may result.

Answer 3

I can pass 2 ways to check it..
1)with your vehicle running remove both positive and negative cables from the battery.If it stalls or runs really ruff the alt. is bad.
2) take an digital meter,set to DC volts ,put black to neg and red to pos.At idle your meter should read 13.5 vol;ts.Pick up the RPMs and it should climb a little more.If it sits at12 volts or less that will show a bad Alt. or a wiring problem..

Answer 4

Easy;

Start the car, then disconnect the battery; if the Alternator is good, the power from it will keep the engine running.

If the Alternator is bad, the engine will die as soon as you disconnect the battery.

Verifying the output with a voltmeter would be better, also.

Answer 5

like any car, when the alternator is on the frits the car will whine. While seated in the interior you will notice that the car Will feel like its draining energy. Your lights will dim and when you use your signal light it will slow dramatically. You can usually purchase a rebuilt alternator for around $80.. Hope I helped! I've had so many go on me over the years that its easy to recognize now.. poor me! LOL

Answer 6

Check if is is sneaking out at night and smoking...then it may be bad
Check if it is selling drugs or other contraband on the streets...then it is definately bad.

Seriously, there should be a manual on the model, but usually a test for a bad alternator is to put a voltmeter on it and check if the range is between 11.8-12.2 volts. The range may vary.

Answer 7

You're still driving a 28 year old car? Unhook the battery,if it dies, the alt. is not putting out. If you have an Auto-Zone in your area, go there, they will check it for free and hope you will buy there....

Answer 8

several ways:

with car running, disconnect battery cable. if car cuts off, alt. is not working

with car running, there is an electromagnet on the back center of alt., put a steel object up to magnet, if it attracts, alt is good.

check your gauges on your dash(if you have them), alt should be putting out about 14 volts

use a volt merer on it, clip to large wire on back of alt, should read about 14 volts.

remove alt , and take it to an auto parts store, many of them have tester.

***edit** bad battery or bad battery connection is more common problem than bad alt.

Answer 9

Pull off one of the battery cables while the car is running, if the car dies then more then likely the alternator is bad

Answer 10

If you don't have a tester,start the car and turn on the headlights.Look at them then turn on the radio,heater and whatever other accessories you have. If the lights dim then your charging system has a problem.