So, technically, pulling a terminal WILL test it.. if other things start smoking, the alternator must be working. ;)
Not that I agree that it ruins things, but I know that I have tried this on other cars with known good alternators and it still stopped running, so not a definitive test across the board. Wallyman [email protected] Sent by: [email protected] 06/27/2011 12:43 PM To [email protected], [email protected] cc Subject Re: Checking alternator? Taking the battery terminal off while the engine is running is about the worst thing you can do in any modern car. Do you have any idea how many electronic components I had changed through the years because the owner thought this was a good way to check the alt? Taking either battery terminal off while running will in most cases make the alternator full feild itself. That means at idle, voltage will be about 18-20 volts through the car. If you happens to raise the rpm just alittle, the output will jump significantly to 20+. Most modules can handle 16-17, but after that pray. Raj Larry, thanks for clarifying for me. Trying to do 3 things at once does not work. Lloyd -----Original Message----- From: [email protected] [mailto:[email protected]]On Behalf Of Larry Alster Sent: Sunday, June 26, 2011 3:12 PM To: 'Eric Schieb'; [email protected] Subject: RE: Checking alternator? I think Lloyd means taking the negative off the battery so the car is running on the alternator only and not drawing from the battery. Larry Alster 91 Miata White Knight 92 Miata Silver Bullet 92 Miata Honey B 04 MSM MX-5 Whooosh 06 WRX STi Subie -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Eric Schieb Sent: Sunday, June 26, 2011 3:07 PM To: [email protected] Subject: Re: Checking alternator? Which cable is the "negative cable"? I suspect on a '91 that there is a large positive output wire headed to the battery, a small wire to energize the field in the alternator, and a small wire to run the lamp on the dash. The ground is handled through the frame of the alternator. Alternator manufacturers typically DO NOT recommend disconnecting the large wire while the engine is running. They typically talk about voltage spikes damaging things. Can you put a volt meter on the output wire? If you are getting voltage levels above what the battery was at before starting the car, the alternator is outputting something. However, this is based on experience with alternators of that period and not specific Miata knowledge. Eric Schieb On 6/26/2011 3:52 PM, Lloyd Broussard wrote: > I think my alternator is going out. Will removing the negative cable while > the engine running tell me if it's putting out juice. I know this is really > old school, but it's a quick check. > > The car is a '91 with a Link computer. > > > _______________________________________________ > Miatapower mailing list > [email protected] > http://list.miatapower.net/cgi-bin/mailman/listinfo/miatapower _______________________________________________ Miatapower mailing list [email protected] http://list.miatapower.net/cgi-bin/mailman/listinfo/miatapower _______________________________________________ Miatapower mailing list [email protected] http://list.miatapower.net/cgi-bin/mailman/listinfo/miatapower _______________________________________________ Miatapower mailing list [email protected] http://list.miatapower.net/cgi-bin/mailman -----Original Message----- From: Lloyd Broussard <[email protected]> To: Larry Alster <[email protected]>; miatapower <[email protected]> Sent: Sun, Jun 26, 2011 7:32 pm Subject: RE: Checking alternator? Larry, thanks for clarifying for me. Trying to do 3 things at once does not work. Lloyd -----Original Message----- From: [email protected] [mailto:[email protected]]On Behalf Of Larry Alster Sent: Sunday, June 26, 2011 3:12 PM To: 'Eric Schieb'; [email protected] Subject: RE: Checking alternator? I think Lloyd means taking the negative off the battery so the car is running on the alternator only and not drawing from the battery. Larry Alster 91 Miata White Knight 92 Miata Silver Bullet 92 Miata Honey B 04 MSM MX-5 Whooosh 06 WRX STi Subie -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Eric Schieb Sent: Sunday, June 26, 2011 3:07 PM To: [email protected] Subject: Re: Checking alternator? Which cable is the "negative cable"? I suspect on a '91 that there is a large positive output wire headed to the battery, a small wire to energize the field in the alternator, and a small wire to run the lamp on the dash. The ground is handled through the frame of the alternator. Alternator manufacturers typically DO NOT recommend disconnecting the large wire while the engine is running. They typically talk about voltage spikes damaging things. Can you put a volt meter on the output wire? If you are getting voltage levels above what the battery was at before starting the car, the alternator is outputting something. However, this is based on experience with alternators of that period and not specific Miata knowledge. Eric Schieb On 6/26/2011 3:52 PM, Lloyd Broussard wrote: > I think my alternator is going out. Will removing the negative cable while > the engine running tell me if it's putting out juice. I know this is really > old school, but it's a quick check. > > The car is a '91 with a Link computer. > > > _______________________________________________ > Miatapower mailing list > [email protected] > http://list.miatapower.net/cgi-bin/mailman/listinfo/miatapower _______________________________________________ Miatapower mailing list [email protected] http://list.miatapower.net/cgi-bin/mailman/listinfo/miatapower _______________________________________________ Miatapower mailing list [email protected] http://list.miatapower.net/cgi-bin/mailman/listinfo/miatapower _______________________________________________ Miatapower mailing list [email protected] http://list.miatapower.net/cgi-bin/mailman/listinfo/miatapower _______________________________________________ Miatapower mailing list [email protected] http://list.miatapower.net/cgi-bin/mailman/listinfo/miatapower
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