Diode test 67 61 amp alternator
Is there a way to test the diodes on the alternator at home? My mechanic told me that the occasional whine/whistle noise I hear (he also heard) was 1 or more diodes going bad. Engine and transmission are currently out of the car for rebuild. I carried it to an alternator/starter rebuild shop on Friday to have it tested. The shop owner told me that it was fine, only that it was not putting out the 61 amps for an A. C. car alternator. He did not say what it was actually putting out, only that if it was keeping the battery charged while using the AC then not to worry about it. He was very busy, so I didn't push the issue as he didn't charge me anything for the check. I just want to make sure everything is ok with the alt. Would bad diodes make the alt put out less that 61 amps or only affect the voltage output? Also, can diodes that that are begining to fail work part time, as during his test, or do they fail completely. This noise is more when the car is 1st started or when revving the engine. I checked the belt and it only had approx 3/8" deflection. Also used some light candle wax on the bottom side of the belt for lubrication, but it would still do it. The thing that concerns me now is, if the alternator is not putting out 61 amps, how soon before other issues arise, such as a bad battery, etc?
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Re: Diode test 67 61 amp alternator
Thanks Joe, unfortunately, I don't have either of these manuals. Used to have the Service Manual and lent it to a friend who moved away without ever returning it. I'm thinking that the whine could have been a vacuum leak in the carb or PS pump, rather than the diodes. However, I'm more concerned about the output being less than 61amps and was wondering if a bad diode(s) could cause the lower amperage output if one or more are in the process of failing. The alternator has less than 1,500 miles on it since a professional rebuild by John Pirkle shortly before his passing, so, I wouldn't think it would be a diode (but, who knows w/o checking). The only other possibility is if something was mixed up on reassembly.Comment
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Re: Diode test 67 61 amp alternator
I didn't test it when it was new, but in 1990 I tested the original 1100884 61amp alternator in my 1970; and it produced 63amps at 2500 engine RPM on a SUN VAT 40 tester. I have no doubt it produced more or less 61amps in 1970. I would also expect similar results today. Delcotron SI alternators are a robust design and they should meet design specifications baring any abuse. And just for the record abuse includes trying to charge a dead battery with the alternator. Delcotrons are not designed to bring a moribund battery back to life. They may do it once, but damage is sure to result from prolonged maximum alternator output. I have never seen a time limited specification, but experience tells me that forcing maximum output for hours on end will lead to component failure. Heat build up is the major issue.
I tested it because at the time I was teaching an Automotive course at my local Community College and I wanted to demonstrate the functions of the VAT 40 to the students. There is nothing like an older Corvette to attract the attention of young (relative to me
) students. I had the same results in the Adult Education class I taught more recently, and some of those students are older than I am.
TerryComment
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Re: Diode test 67 61 amp alternator
Terry,
I agree and a 10-DN alternator like Al has should be able to produce it's rated output.
PeteComment
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Re: Diode test 67 61 amp alternator
Carried it to the local AutoZone today and they put it on their machine. It showed it as a 61amp output alternator on the readout and passed all tests for whatever that's worth. I will continue to use it when the engine is reinstalled and if a problem arises, I'll deal with it at that time. I just may be overthinking the whole thing and trying to make something out of something else.Comment
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