test alternator
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Forum Name: General Discussion
Forum Discription: General Mobile Electronics Questions and Answers
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=95548
Printed Date: May 06, 2024 at 12:07 AM
Topic: test alternator
Posted By: creed2k
Subject: test alternator
Date Posted: July 12, 2007 at 8:49 PM
I've been having some issues with my car that from some reading tells me MIGHT be alternator related... now i have a volt meter, and i was gonna start the car and put the red lead on positive and the black on negative to see what kind of power ratings i get, but what should the volt meter be set on? i have ohms and all kinds of other stuff, where should i set it to do this test?
and also any other tips for what i should look for with my car having weird wiring issues (headlights not working at all, interior lights/radio working on and off)? (99 eclipse)
Replies:
Posted By: bradybuck
Date Posted: July 15, 2007 at 6:15 PM
Set your volt meter to DC volts. If you have a DC volts "range" setting, set it to some where around 20 volts. That should be sufficient.
Tip: Quick alternator test: Start your car. With the car running, remove the positive cable from your battery. If your car cuts of immediately, your do have a problem w/ your alternator.
As far as your wiring issues, have you checked:
1 fuses?
2 make sure you have good ground connection?
3 any other accessories that may have been added since the car was purchased?
Let me know what you find or if you need to post anymore specifics.
Later
Posted By: citrus3000psi
Date Posted: July 17, 2007 at 2:34 PM
I feel you wouldn;t need to take battery cable off. With the car off your battery should read around 12vdc, with the car running it should be at 13-14vdc. Some alternators (due to pullies and design) don't turn fast enough at idle to produce enough juice. Thast why you see peoples headlights get brighter when the take off. So have somone give the car a little gas when you do the test. You can just test off the battery terminals, no need to get the probes down where the alt, at.
Posted By: creed2k
Date Posted: July 18, 2007 at 1:22 PM
I ended up taking it to advance auto and they tested it for me and told me my battery and alternator are fine... 
Posted By: sarcomax
Date Posted: July 19, 2007 at 4:03 PM
Bad grounds and blown fuses could be your problem(s).Since you have a multimeter you can test alot of the stuff yourself. What happened right before the car started acting up? You may have a visit to your mechanic in your future.
Posted By: archemedes
Date Posted: July 19, 2007 at 11:37 PM
bradybuck wrote:
Set your volt meter to DC volts. If you have a DC volts "range" setting, set it to some where around 20 volts. That should be sufficient.
Tip: Quick alternator test: Start your car. With the car running, remove the positive cable from your battery. If your car cuts of immediately, your do have a problem w/ your alternator.
As far as your wiring issues, have you checked:
1 fuses?
2 make sure you have good ground connection?
3 any other accessories that may have been added since the car was purchased?
Let me know what you find or if you need to post anymore specifics.
Later
That testing method may work, but can also kill the alternator, they are designed to see that as a malfunction. All the auto parts stores test them for free, let them
Posted By: Mad Scientists
Date Posted: July 21, 2007 at 3:13 PM
bradybuck wrote:
Set your volt meter to DC volts. If you have a DC volts "range" setting, set it to some where around 20 volts. That should be sufficient.
Tip: Quick alternator test: Start your car. With the car running, remove the positive cable from your battery. If your car cuts of immediately, your do have a problem w/ your alternator.
Please don't unhook the battery when the engine is running.. this was a valid test 50 years ago, but with all the on-board electronics now, it's a fine way to smoke an ECM or something else expensive. Use a voltmeter. Jim
Posted By: creed2k
Date Posted: July 25, 2007 at 11:35 AM
Yeah i didnt do the unhook the battery while the car is running method... seemed risky to me... i took it to advance and all was well, but i ended up finding the problem. 2 power wires running from my fusebox under the hood to the cabin were completely cut in half, i reattached those and its been smooth sailing ever since.
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