Testing alternator.

Bought an '87 Accord hatchback recently (2.0l, 2bbl, 5spd)... owner was selling it because the alternator "didn't work". Seemed to me that it
worked, but not 100%. In any case, I swapped in the alternator from my identical '87 sedan that had just bit the dust, and all was happy until a couple nights ago: charge light flickering, dashlights dim, except when revving high. Typical indication of bad brushes. Figured I was doing okay trying to get home when suddenly the charge light came on solid and wouldn't go out for anything. JUST made it home, engine sputtering every time I hit the brakes.
So today I pulled apart the original alt. and checked it out: diodes all test fine, field windings seem okay, no opens or shorts anywhere. Brushes weren't too badly worn, so not really sure what was wrong with it.
Got the replacement alt. out of the car (finally - some Japanese SOB needs a serious bitchslapping over the layout of that engine) an opened it up... brushes were REALLY worn, but still making contact - barely. Diodes and windings checked okay as well.
Now the only thing I can't test is the voltage regulator. Or can I? With a stanard multimeter, that is, since I don't have a nice super-duper alternator/starter bench tester sitting on my kitchen table...?
I took a few readings across various terminals of both regulators, DMM set to Diode Check, and got several readings that differed between the two... for example, testing from "terminal A" (named arbitrarily for the sake of argument) to terminals B and C on one regulator showed infinite resistance, but on the other, they showed about 1200Mohms aa 1800Mohms, respectively. Reversing the leads, the first regulator showed 1200 and 1500 (B-to-A and C-to-A), but the other, I got 1500M and infinite, respectively. Obviously I don't know which one is "right" reading, and it's not enough to make an intelligent diagnosis.
So... does anyone know of any way I can test the regulator? Or better yet, know how I can hook up the alternator on the bench (ie. what goes to what connections) and test it there, maybe spin it up with my cordless drill?
TIA...
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a lot easier to test it in service with a DMM. However, most major auto parts stores have a test jig, where they can spin the alternator with an electric motor and measure the output under various loads... and they will do it for free.
Mike
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Michael Pardee wrote:

There must be some way to test the regulator module itself - supply juice to the inputs, measure the outputs? As I say, all the other components are fairly "testable" on their own and seem to be fine...
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but I think all of them now are switch mode, pulsing the inductance of the field. You could connect the regulator to the alternator and measure current drain as you turned the input voltage up - the current should drop rapidly as you exceed the regulator point (somewhere around 14 volts).
Mike
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Michael Pardee wrote:

Cool, except it still has to be in the car for that, which in itself is a nightmare, and at that point is wholly inaccessible :) Assuming one determines which connections are which on the thing, too.
I guess that's what I'm really hoping, is to find the pinouts for the module; given those, I may be able to at least tell, without putting it all back together and into the car, whether either of the two regulators I have are *obviously* faulty.
Recall that the original alternator in the car worked intermittantly, and upon disassembly and testing, the brushes seem sufficient and everything else I CAN test (windings, diodes) seems good, so that leaves the regulator as "questionable".
The behaviour of the second one worries me a little, the way it was doing the typical worn-brush thing for only a little while before packing it in completely: again, the brushes are obviously gone, and everything else tests fine, and I don't want to put it all back together and into the car only to discover the regulator is pooched. A simple works/doesn't-works test is all I'm looking for.
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On 2005-05-23 snipped-for-privacy@sedona.net said: >Newsgroups: rec.autos.makers.honda,alt.autos.honda >Michael Pardee wrote:
>> >>>>>Bought an '87 Accord hatchback recently (2.0l, 2bbl, 5spd)... >>>>>owner was selling it because the alternator "didn't work". >>>>>Seemed to me that it worked, but not 100%. In any case, I >>>>>swapped in the alternator from my identical '87 sedan that had >>>>>just bit the dust, and all was happy until a couple nights ago: >>>>>charge light flickering, dashlights dim, except when revving >>>>>high. Typical indication of bad brushes. Figured I was doing >>>>>okay trying to get home when suddenly the charge light came on >>>>>solid and wouldn't go out for anything. JUST made it home, >engine sputtering every time I hit the brakes. >>>> >>>>>So today I pulled apart the original alt. and checked it out: >>>>>diodes all test fine, field windings seem okay, no opens or >>>>>shorts anywhere. Brushes weren't too badly worn, so not really >sure what was wrong with it. >>>> >>>>>Got the replacement alt. out of the car (finally - some >>>>>Japanese SOB needs a serious bitchslapping over the layout of >>>>>that engine) an opened it up... brushes were REALLY worn, but >>>>>still making contact - barely. Diodes and windings checked okay >as well. >>>> >>>>>Now the only thing I can't test is the voltage regulator. Or >>>>>can I? With a stanard multimeter, that is, since I don't have a >>>>>nice super-duper alternator/starter bench tester sitting on my >kitchen table...? >>>> >>>>>I took a few readings across various terminals of both >>>>>regulators, DMM set to Diode Check, and got several readings >>>>>that differed between the two... for example, testing from >>>>>"terminal A" (named arbitrarily for the sake of argument) to >>>>>terminals B and C on one regulator showed infinite resistance, >>>>>but on the other, they showed about 1200Mohms aa 1800Mohms, >>>>>respectively. Reversing the leads, the first regulator showed >>>>>1200 and 1500 (B-to-A and C-to-A), but the other, I got 1500M >>>>>and infinite, respectively. Obviously I don't know which one >is "right" reading, and it's not enough to make an intelligent >>>>>diagnosis. >>>> So... does anyone know of any way I can test >>>>>the regulator? Or better yet, know how I can hook up the >>>>>alternator on the bench (ie. what goes to what connections) and >>>>>test it there, maybe spin it up with my cordless drill? >>>>>TIA... >>>>There isn't any great way to test it on the bench with common >>>>tools - it is a lot easier to test it in service with a DMM. >>>>However, most major auto parts stores have a test jig, where >>>>they can spin the alternator with an electric motor and measure >>>>the output under various loads... and they will do it for free. >>>There must be some way to test the regulator module itself - >>>supply juice to the inputs, measure the outputs? As I say, all >>>the other components are fairly "testable" on their own and seem >to be fine... >> >> Maybe, but I'm not sure. Some old voltage regulators used analog >>drivers, but I think all of them now are switch mode, pulsing the >>inductance of the field. You could connect the regulator to the >>alternator and measure current drain as you turned the input >>voltage up - the current should drop rapidly as you exceed the >regulator point (somewhere around 14 volts). >Cool, except it still has to be in the car for that, which in >itself is a nightmare, and at that point is wholly inaccessible :) >Assuming one determines which connections are which on the thing, >too. >I guess that's what I'm really hoping, is to find the pinouts for >the module; given those, I may be able to at least tell, without >putting it all back together and into the car, whether either of >the two regulators I have are *obviously* faulty. >Recall that the original alternator in the car worked >intermittantly, and upon disassembly and testing, the brushes seem >sufficient and everything else I CAN test (windings, diodes) seems >good, so that leaves the regulator as "questionable". >The behaviour of the second one worries me a little, the way it was >doing the typical worn-brush thing for only a little while before >packing it in completely: again, the brushes are obviously gone, and >everything else tests fine, and I don't want to put it all back >together and into the car only to discover the regulator is pooched. >A simple works/doesn't-works test is all I'm looking for. >--- Is there anything wrong with taking your alternator to a parts store for testing on their machine? Next town over has a Checker parts store with at least one real competent guy who would test yours.
Tom Willmon near Mountainair, (mid) New Mexico, USA
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snipped-for-privacy@cybermesa.net wrote:

Did that. Tested fine. Put it back in the car. Now it works intermittantly. It'll run 13V at idle, up to 14.1 at speed, but if I start turning stuff on (lights, blower) it'll drop below 12V; ie. not charging at all. Turning everything off again, it takes upwards of 30s of revving to start charging again.
I'm wondering if a brush isn't in quite right, as there's a 'ticking' sound coming from it now that changes with engine speed.
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Unless you know how to rebuilt it yourself, I advise you to buy a new alternator. Another option is to visit a car junk yard. If the manager or owner is on a database of thousands of junk yard, he can order you one even if he does not have one in stock. The owner or manager may even provide a warranty for it in case it does not work. I once found a wrecked car just like the one I owned at that time and got lots of parts off of it for almost nothing.
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