Quick Alternator testing question
Thread Starter
Launching!
Joined: Dec 2001
Posts: 259
Likes: 1
From: Durham, NC
Quick Alternator testing question No parts stores will test my (99 camaro) alternator - they claim it's too new, they don't have the adapters for it (which I think is BS, anyway....).
So, I poked around at it myself. No idea what I'm looking for. Problem is a suspicious battery drainage issue. Could be a short or bad ground someplace, OR, it could be the alt.
SO, my alternator shows some continuity between the Pos+ post and the case. Not 100%, just a little bit. To me, this seems bad. But I have no idea.
Alternators are expensive, and I am poor. What do you guys think?
So, I poked around at it myself. No idea what I'm looking for. Problem is a suspicious battery drainage issue. Could be a short or bad ground someplace, OR, it could be the alt.
SO, my alternator shows some continuity between the Pos+ post and the case. Not 100%, just a little bit. To me, this seems bad. But I have no idea.
Alternators are expensive, and I am poor. What do you guys think?
Thread Starter
Launching!
Joined: Dec 2001
Posts: 259
Likes: 1
From: Durham, NC
Re: Quick Alternator testing question Hrm, no one knows? I found something that suggested there would be voltage "leak" from the Pos+ to the case - on the order of a few millivolts.
I'm not really excited about re-installing the alt to do diagnostics, only to have it drain my battery again. But, I suppose if that's the only way.... I guess I would know for sure it was bad at that point.
I'm not really excited about re-installing the alt to do diagnostics, only to have it drain my battery again. But, I suppose if that's the only way.... I guess I would know for sure it was bad at that point.
Re: Quick Alternator testing question well.....wow....I have no idea....only thing I know to do it strap it back on and take it to a dealership <img border="0" title="" alt="[Frown]" src="gr_sad.gif" /> . Here is a TTT for you.
Good luck, post what you find
Chris
Good luck, post what you find
Chris
Re: Quick Alternator testing question A way that I use to tell if the alternator is bad, is to start up the car, and once its running disconnect the battery. If the car still runs, its the battery. If it dies, its the alternator. Hopes this helps <img border="0" alt="[driving]" title="" src="graemlins/gr_driving3.gif" />
On The Tree
Joined: Jan 2003
Posts: 131
Likes: 0
From: ft. worth TX.
Re: Quick Alternator testing question Don't i repeat don't do this you can really screw the computer up in your truck if you do! The computer can only take a very slow voltage drop and if you take the pos terminal off of your battery with the truck running your probably going to screw your computer. Use a voltmeter and check to see what amperage your getting when the vehicle is running then turn off the motor and do the same to your battery if the readdings are the same its probably your alt. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />
Re: Quick Alternator testing question </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by pony killer:
<strong> Don't i repeat don't do this you can really screw the computer up in your truck if you do! The computer can only take a very slow voltage drop and if you take the pos terminal off of your battery with the truck running your probably going to screw your computer. Use a voltmeter and check to see what amperage your getting when the vehicle is running then turn off the motor and do the same to your battery if the readdings are the same its probably your alt. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" /> </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Thanks for the heads up <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />
<strong> Don't i repeat don't do this you can really screw the computer up in your truck if you do! The computer can only take a very slow voltage drop and if you take the pos terminal off of your battery with the truck running your probably going to screw your computer. Use a voltmeter and check to see what amperage your getting when the vehicle is running then turn off the motor and do the same to your battery if the readdings are the same its probably your alt. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" /> </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Thanks for the heads up <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />
Re: Quick Alternator testing question Use a Voltmeter to check you alt output with engine running: 14VDC is good. It takes more than 12 volts to charge a 12 volt battery so less than 14 VDC is not enough. If you Batt is being discharged over time you have a device that is "ON" when it should be "OFF". If it were SHORTED to ground it would blow a fuse UNLESS the current draw is less than the rating of the fuse. If it is a direct short to ground it is going to blow a fuse in any case. If you have a slow drain on your battery you need to start pulling fuses. If you pull the fuses in your garage at nite with the lites off you may see a small arc as you remove a fuse that is NOT supposed to be drawing current at that time. That ain't good. That device will kill your batt over time. You then look on a schematic to find out what devices are on that circuit and check to see if they are turned "ON" when they should be "OFF". That's the device that's killing your battery. Now you have to figure out why that device is "ON" and repair that problem. You can also use an AMMETER
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Thread Starter
Launching!
Joined: Dec 2001
Posts: 259
Likes: 1
From: Durham, NC
Re: Quick Alternator testing question The troubling thing is that the battery stays nice and topped off with the alt disconnected. Granted, I have yet to reconnect it again to fully test this theory. I also only have 6 circuits connected, so those are really easy to check.
I think I am just going to take the alt to a store during the weekday and hope that someone competent will be available then to actually test it. I will definitely NOT buy another one without evidence that mine is hosed.
Anyway, I appreciate the tips.
(BTW, it's not really a Z71 truck. It's a 71 Z, and it's currently "off the road" (on jackstands), hence the use of the avatar. No Datsun avatars are available for some reason <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> )
I think I am just going to take the alt to a store during the weekday and hope that someone competent will be available then to actually test it. I will definitely NOT buy another one without evidence that mine is hosed.
Anyway, I appreciate the tips.
(BTW, it's not really a Z71 truck. It's a 71 Z, and it's currently "off the road" (on jackstands), hence the use of the avatar. No Datsun avatars are available for some reason <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> )
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