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Testing an alternator: Using a stiffening capacitor
Hi all,
I've heard that you can't disconnect the positive terminal of a battery to test an alternator on newer cars: http://www.repairfaq.org/ELE/F_Car_B...CARBATTERY_031 If I strapped one of those stiffening capacitors (http://en.wikipedia.org/wiki/Stiffening_capacitor) for car audio (1-2 farads) across the positive and negative terminals, would I be able to protect my electronic circuits enough to be able to disconnect the positive terminal from the battery to test the alternator? My suspicion is that it would, but I thought I'd throw this question out there before I tried it... Has anyone tried this? Yonkster Youler |
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#3
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Testing an alternator: Using a stiffening capacitor
> wrote in message oups.com... > Hi all, > > > I've heard that you can't disconnect the positive terminal of a battery > to test an alternator on newer cars: > > http://www.repairfaq.org/ELE/F_Car_B...CARBATTERY_031 > > If I strapped one of those stiffening capacitors > (http://en.wikipedia.org/wiki/Stiffening_capacitor) for car audio (1-2 > farads) across the positive and negative terminals, would I be able to > protect my electronic circuits enough to be able to disconnect the > positive terminal from the battery to test the alternator? My > suspicion is that it would, but I thought I'd throw this question out > there before I tried it... > > > Has anyone tried this? > > > > Yonkster Youler > Why would you even want to. The alternator can be tested without disconecting the battery. Actually the battery should be tested first then the altenator. go here to learn how: http://www.cdxetextbook.com/electric...arging/01.html -- Kevin Mouton Automotive Technology Instructor "If women don't find you handsome, they should at least find you handy" Red Green |
#4
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Testing an alternator: Using a stiffening capacitor
For less than five bucks you can get a multimeter which will allow you
to test the voltage and see what is going on. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06 http://www.imagestation.com/album/pi...?id=2115147590 (More Off Road album links at bottom of the view page) wrote: > > Hi all, > > I've heard that you can't disconnect the positive terminal of a battery > to test an alternator on newer cars: > > http://www.repairfaq.org/ELE/F_Car_B...CARBATTERY_031 > > If I strapped one of those stiffening capacitors > (http://en.wikipedia.org/wiki/Stiffening_capacitor) for car audio (1-2 > farads) across the positive and negative terminals, would I be able to > protect my electronic circuits enough to be able to disconnect the > positive terminal from the battery to test the alternator? My > suspicion is that it would, but I thought I'd throw this question out > there before I tried it... > > > Has anyone tried this? > > Yonkster Youler |
#5
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Testing an alternator: Using a stiffening capacitor
On Thu, 01 Jun 2006 09:57:52 -0400, Mike Romain > wrote:
>For less than five bucks you can get a multimeter which will allow you >to test the voltage and see what is going on. Don't forget to put on a load such as the headlights and rear window defroster. A cheap meter won't tell you if the alternator has a blown output diode or two. Without a load, you might still read 14.4V on an alternator that'll let the battery run down while you're driving with headlights. |
#6
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Testing an alternator: Using a stiffening capacitor
On Thu, 01 Jun 2006 15:07:40 GMT, AZ Nomad >
wrote: >On Thu, 01 Jun 2006 09:57:52 -0400, Mike Romain > wrote: > > >>For less than five bucks you can get a multimeter which will allow you >>to test the voltage and see what is going on. > >Don't forget to put on a load such as the headlights and rear window >defroster. A cheap meter won't tell you if the alternator has a blown >output diode or two. Without a load, you might still read 14.4V on >an alternator that'll let the battery run down while you're driving >with headlights. I just turn =all= the electrics on, everything including rear window defogger, headlights on hi beam, etc etc and put a clamp meter on the alternator B+ wire to the battery. "Normal" is 66 amperes. If I'm reading less than that, then I will know there is a problem. So, when you check your vehicle, IF you have a known good reference value for this or that, a simple clamp type ammeter will tell you if your alternator is working correctly I do believe. Then, you can check for more or less than 100 ma AC at the battery...by putting the voltmeter across the +/- while the meter is switched to AC. If you see more than 100 ma AC then there is something wrong with the alternator somewhere. Lg |
#7
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Testing an alternator: Using a stiffening capacitor
On Thu, 01 Jun 2006 17:38:52 -0500, Lawrence Glickman
> wrote: >On Thu, 01 Jun 2006 15:07:40 GMT, AZ Nomad > >wrote: > >>On Thu, 01 Jun 2006 09:57:52 -0400, Mike Romain > wrote: >> >> >>>For less than five bucks you can get a multimeter which will allow you >>>to test the voltage and see what is going on. >> >>Don't forget to put on a load such as the headlights and rear window >>defroster. A cheap meter won't tell you if the alternator has a blown >>output diode or two. Without a load, you might still read 14.4V on >>an alternator that'll let the battery run down while you're driving >>with headlights. > >I just turn =all= the electrics on, everything including rear window >defogger, headlights on hi beam, etc etc and put a clamp meter on the >alternator B+ wire to the battery. "Normal" is 66 amperes. If I'm >reading less than that, then I will know there is a problem. > >So, when you check your vehicle, IF you have a known good reference >value for this or that, a simple clamp type ammeter will tell you if >your alternator is working correctly I do believe. ================================================== =============== Then, you can check for more or less than 100 mv AC at the battery...by putting the voltmeter across the +/- while the meter is switched to AC. If you see more than 100 mv AC then there is something wrong with the alternator somewhere. > >Lg > |
#8
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Testing an alternator: Using a stiffening capacitor
On Thu, 01 Jun 2006 18:20:43 -0500, Lawrence Glickman > wrote:
>On Thu, 01 Jun 2006 17:38:52 -0500, Lawrence Glickman > wrote: >>On Thu, 01 Jun 2006 15:07:40 GMT, AZ Nomad > >>wrote: >> >>>On Thu, 01 Jun 2006 09:57:52 -0400, Mike Romain > wrote: >>> >>> >>>>For less than five bucks you can get a multimeter which will allow you >>>>to test the voltage and see what is going on. >>> >>>Don't forget to put on a load such as the headlights and rear window >>>defroster. A cheap meter won't tell you if the alternator has a blown >>>output diode or two. Without a load, you might still read 14.4V on >>>an alternator that'll let the battery run down while you're driving >>>with headlights. >> >>I just turn =all= the electrics on, everything including rear window >>defogger, headlights on hi beam, etc etc and put a clamp meter on the >>alternator B+ wire to the battery. "Normal" is 66 amperes. If I'm >>reading less than that, then I will know there is a problem. >> >>So, when you check your vehicle, IF you have a known good reference >>value for this or that, a simple clamp type ammeter will tell you if >>your alternator is working correctly I do believe. >================================================= ================ >Then, you can check for more or less than 100 mv AC at the >battery...by putting the voltmeter across the +/- while the meter is >switched to AC. If you see more than 100 mv AC then there is >something wrong with the alternator somewhere. More like 300-500mv. 100mv isn't much ripple and is normal. |
#9
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Testing an alternator: Using a stiffening capacitor
On Fri, 02 Jun 2006 01:24:16 GMT, AZ Nomad >
wrote: >On Thu, 01 Jun 2006 18:20:43 -0500, Lawrence Glickman > wrote: > > >>On Thu, 01 Jun 2006 17:38:52 -0500, Lawrence Glickman > wrote: > >>>On Thu, 01 Jun 2006 15:07:40 GMT, AZ Nomad > >>>wrote: >>> >>>>On Thu, 01 Jun 2006 09:57:52 -0400, Mike Romain > wrote: >>>> >>>> >>>>>For less than five bucks you can get a multimeter which will allow you >>>>>to test the voltage and see what is going on. >>>> >>>>Don't forget to put on a load such as the headlights and rear window >>>>defroster. A cheap meter won't tell you if the alternator has a blown >>>>output diode or two. Without a load, you might still read 14.4V on >>>>an alternator that'll let the battery run down while you're driving >>>>with headlights. >>> >>>I just turn =all= the electrics on, everything including rear window >>>defogger, headlights on hi beam, etc etc and put a clamp meter on the >>>alternator B+ wire to the battery. "Normal" is 66 amperes. If I'm >>>reading less than that, then I will know there is a problem. >>> >>>So, when you check your vehicle, IF you have a known good reference >>>value for this or that, a simple clamp type ammeter will tell you if >>>your alternator is working correctly I do believe. >>================================================ ================= >>Then, you can check for more or less than 100 mv AC at the >>battery...by putting the voltmeter across the +/- while the meter is >>switched to AC. If you see more than 100 mv AC then there is >>something wrong with the alternator somewhere. ================================================== ================== >More like 300-500mv. >100mv isn't much ripple and is normal. Okay, thanks. Just going by what aarcuda mentioned the other day in another thread. I haven't even measured the "AC component" of the alternator across the battery yet. I don't know why. The car is in the garage about 20 feet away from me...one would think I was _curious_. Evidently not at the moment ;-) Lg |
#10
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Testing an alternator: Using a stiffening capacitor
On Thu, 01 Jun 2006 21:32:24 -0500, Lawrence Glickman
> wrote: >On Fri, 02 Jun 2006 01:24:16 GMT, AZ Nomad > >wrote: > >>On Thu, 01 Jun 2006 18:20:43 -0500, Lawrence Glickman > wrote: >> >> >>>On Thu, 01 Jun 2006 17:38:52 -0500, Lawrence Glickman > wrote: >> >>>>On Thu, 01 Jun 2006 15:07:40 GMT, AZ Nomad > >>>>wrote: >>>> >>>>>On Thu, 01 Jun 2006 09:57:52 -0400, Mike Romain > wrote: >>>>> >>>>> >>>>>>For less than five bucks you can get a multimeter which will allow you >>>>>>to test the voltage and see what is going on. >>>>> >>>>>Don't forget to put on a load such as the headlights and rear window >>>>>defroster. A cheap meter won't tell you if the alternator has a blown >>>>>output diode or two. Without a load, you might still read 14.4V on >>>>>an alternator that'll let the battery run down while you're driving >>>>>with headlights. >>>> >>>>I just turn =all= the electrics on, everything including rear window >>>>defogger, headlights on hi beam, etc etc and put a clamp meter on the >>>>alternator B+ wire to the battery. "Normal" is 66 amperes. If I'm >>>>reading less than that, then I will know there is a problem. >>>> >>>>So, when you check your vehicle, IF you have a known good reference >>>>value for this or that, a simple clamp type ammeter will tell you if >>>>your alternator is working correctly I do believe. >>>=============================================== ================== >>>Then, you can check for more or less than 100 mv AC at the >>>battery...by putting the voltmeter across the +/- while the meter is >>>switched to AC. If you see more than 100 mv AC then there is >>>something wrong with the alternator somewhere. > >================================================= =================== >>More like 300-500mv. >>100mv isn't much ripple and is normal. > >Okay, thanks. Just going by what aarcuda mentioned the other day in >another thread. I haven't even measured the "AC component" of the >alternator across the battery yet. I don't know why. The car is in >the garage about 20 feet away from me...one would think I was >_curious_. Evidently not at the moment ;-) > >Lg ================================================== ====================== UPDATE: I just measured the AC component on 61 AMPERES DC coming out of my alternator, and I get 20 ( Twenty ) milliVolts of AC ripple from the alternator when its' B+ is connected to, and measured at, the battery. So...it looks to me like aarcuda was/is correct. Anything over 100 millivolts AC means something is not right with your charging system. Lg |
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