 Easy Alternator test? |
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| ChrisReale |
 Nov 16 2006, 04:42 PM
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Sleazy  Group: Members Posts: 2,665 Joined: 20-January 03 From: San Francisco Member No.: 176  |
Is there an easy multi-meter test you can do to see if the alternator has crapped out? I guess the fact that my battery doesn't charge is proof enough, but I just wanna make sure.
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| Spoke |
Nov 17 2006, 09:31 AM
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#2
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Jerry Group: Members Posts: 7,279 Joined: 29-October 04 From: Allentown, PA Member No.: 3,031 Region Association: None 
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To check the alternator assuming that the belt is ok and everything is mechanically sound, do a test which simulates the voltage regulator applying voltage to the armature to increase alternator voltage.
Sorry, I don't have access to my schematic. (It's at home and I'm in South Korea) So my instruction will lack the actual wire designation. I did this test to separate voltage regulator issues from alternator issues. My low voltage issue was the voltage regulator. Look at the schematic for the voltage regulator (VR). The top most connection from the alternator provides power to the VR and senses alternator voltage. The center lead in the schematic is the armature positive lead and inside the VR, this lead is connected to what looks like the contacts of a relay. The VR connects this lead to the alternator voltage to increase the voltage and opens the lead if the voltage is sufficient. If you connect the armature positive lead to the top most connection from the alternator, you will simulate the VR trying to increase alternator voltage. Connect the leads together first then start the engine. If the alternator is ok, the battery voltage should rise to about 15-16 volts. If it doesn't, you either have done this test incorrectly or your alternator is bad. If you are unsure about the VR connections, do not do this test. Spoke |
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Posts in this topic
ChrisReale Easy Alternator test? Nov 16 2006, 04:42 PM
So.Cal.914 When your car is running put the probes on the pos... Nov 16 2006, 04:52 PM Rand Also check your voltage regulator before replacing... Nov 16 2006, 04:58 PM
Michael N
Also check your voltage regulator before replacin... Jan 9 2015, 12:11 AM vsg914 I assume you checked the belt first? Nov 16 2006, 05:15 PM Scott-thundercat check the battery voltage before it's started ... Nov 16 2006, 05:44 PM McMark As mentioned, the voltage regulator can be bad as ... Nov 16 2006, 05:59 PM Brew QUOTE
McMark Nope, if the bulb is burned out the alternator wil... Nov 16 2006, 10:08 PM SGB Absolutely true. As McMark says, But it RARElY b... Nov 16 2006, 10:25 PM cary Revive an old thread ..............
Just trailered... Jan 8 2015, 11:45 PM cary Did that cause the alternator light not to fire up... Jan 9 2015, 12:15 AM Dave_Darling Yes, when the VR is not plugged in, the alternator... Jan 9 2015, 11:18 AM cary
Yes, when the VR is not plugged in, the alternato... Jan 9 2015, 12:30 PM type47 I'd like to listen to a discussion on how the ... Jan 9 2015, 11:44 AM Dave_Darling
I'd like to listen to a discussion on how the... Jan 9 2015, 02:35 PM mikesmith
I believe the alt light runs off of the alternato... Jan 10 2015, 12:54 PM cary Back in business.
The new Beru VR positions furth... Jan 9 2015, 09:13 PM rhodyguy Happy motoring! Jan 10 2015, 10:35 AM jdlmodelt Okay, alternator wasn't charging. I put 12.5Vd... Jan 3 2020, 04:14 PM |
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