Would a Code 53 (system overvoltage) mean that the AMPS coming out of the alt would also be too high ??

Autozone and a couple other local places say they can test my alternator for free at their stores if I just bring it in, but they can only test amperage. To test volts, I need the alt to be in the car with the engine running (not an option with my car currently unless I want to risk driving it about a mile to the store).

Is it possible to test for voltage output with the alt out? Is it just a matter of calling enough parts stores until i find one that can test voltage, not just amps ?

Thanks. Every day I am one day closer to driving my GTA again !





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88 GTA Charcoal Grey Bone Stock except for loose muffler which makes it a bit louder than normal.

 

I read your other post about the same problem. To answer your question, no, you cannot determine voltage by just the amperage, and no, the ECM is not concerned with the amperage, only the voltage. While voltage is directly related to amperage (and also resistance, but I'm trying to keep this simple), the output amperage will increase with an increase in voltage (presuming the resistance remains the same). The output of a properly working alternator is a constant voltage (typically 13.8 - 14.5 volts). The amperage will take care of itself, based upon the load, or current demand. In other words, the amperage is not regulated, just the voltage.

I guess testing the alternator would be better than nothing. I am surprised that whoever makes those testers does not have a voltage function. That is ridicluous. It would only cost a couple dollars more to include that test, and is as important if not more so than the current output. If they don't test the voltage, I would ask them how they determine if the voltage regulator is working? They do test the voltage regulator when they do this test, don't they?

If not, then the thest would probably not be worth the effort to even remove the alternator. Check a starter/alternator shop and see what they say. They are generally more professional and I'm sure they would be testing for voltage.

Let us know what you find.

EDIT:
Oops, your last question about being able to test for voltage with the alternator out of the car. Yes, and it is very easy. Simply connect one lead of a voltmeter to the output stud and the other lead to the case ground and read the output.

[This message has been edited by Stuart Moss (edited July 19, 2001).]

 

OK. Thanks. Then what about testing for voltage with my voltmeter, while the alt is still in the car? Can I just turn on the ignition and connect my voltmeter leads to the alt ?

Thnaks a ton.



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88 GTA Charcoal Grey Bone Stock except for loose muffler which makes it a bit louder than normal.

 

Sure. For the most accurate measurement, connect to the output stud and alternator ground. Otherwise, any other point like the battery terminals will be okay. Generally, depending upon the voltage drop due to the added wiring, the voltage should be within a few tenths (0.2 - 0.4) of a volt.

If you test on the car and think that the alternator output is too high, start the car with a lot of accessories "on". This will load the alternator down to help keep the voltage down (in case it is putting out too much). Be sure to keep the car at idle. Do not rev it up as this will increase the voltage. Now measure the voltage. It should be around 12.5 - 14.8 volts. If it is in this range, slowly rev up the engine and see if the voltage remains under about 14.8 volts - certainly under 15.0 or 15.1 volts. Anything over 15.0 volts, turn off the engine and test the alternator out of the vehicle. If the alternator has been running this way, the damage (ECM?) has probably already been done, so the risk, IMO, would be small.

 

I work at an auto parts store and our tester shows voltage. I work at Checker auto.

 

I don't know where you live, but if you go to a CSK (checkers, schucks, or kragen) chain store, their machines measure voltage and not amperage.

 

I had AutoZone test mine and they tested the voltage. I think they (the people you talked to) got the names mixed up. You can't test amps unless there is a load on the alt. That is what you test for while the alt. is in the car. They must be thinking of the starter tester they have. It puts a load on the "battery" to obtain the neccessary amps to turn the starter. They should be able to tell you the voltage output of the alt, since it is the most important measurement. The needle guage they use is set up for both readings though. They just gotta know which one to read. "The top or bottom #s?"

[This message has been edited by AJ_92RS (edited July 19, 2001).]

 

Thanks, guys, for all the info. AJ, how do you make that green face with the rolling eyes ? I need some comic relief lately.

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88 GTA Charcoal Grey Bone Stock except for loose muffler which makes it a bit louder than normal.

 

Goodness, if they don't even know the difference between amperes and voltage, how much confidence will you have when they determine the condition of the alternator?

The question is, of course, rhetorical.

 

Just got back from Advance Auto. They have an alt tester machine there that spins the alt. The guage has volts and amps clearly marked all over it, but the tech there said the trainers told them to ignore the volts !!! Must be a sofware flaw or something. They said I had to have the alt in the car with the engine running to test the volts. Guess I'll call the Zone and see what they can do for me.

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88 GTA Charcoal Grey Bone Stock except for loose muffler which makes it a bit louder than normal.