Joined: Feb 17, 2012 Posts: 530 Location: Del City, OK
Posted: Wed May 12, 2021 6:07 pm Post subject: Generator Testing
Well, I am slowly working out the bugs on my M-38A1, had a fuel line leak and pinion seal bad. Got those done today.
Checked batteries and found them way down (New less than a month ago). Checked charging system and tested the generator output (used test procedures in download section). I am hoping I did this right. I connected my adapter to the generator output and started jeep. I did not connect the other end of the test cable to the voltage regulator. Had the field and armature points open per the procedure. Measured 1.8 volts and if I revved the engine up I get max of 4 volts plus a bit more.
I am guessing that the generator is not producing an output. Now to rebuild or have rebuilt. New ones are $475-500 depending on where to get it.
Question is did I do this right, or do I need to retest with cables connected.
Also where can I get a rebuild kit if it is bad...
TIA _________________ Hal, KB1ZQ
TSGT, USAF (Ret)
1952 M-38 CDN CAR 52-31313
1952 M-100 Strick #104
1951 Willys Wagon (For Sale)
1954 Willys M38A1 201001205
Tornado Alley
Del City, OK
Can you post the link you used to download the test procedures. Or better yet post a scan of the page that this test you did is on.
I would never condemn a generator without first performing a "Full field test". _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
I was really not interested in proof reading the entire document to determine which step you published in post above. I am trying to offer some assistance here.
Can you reply to my note to always do a full field test? Ie you have already done it or not? _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Joined: Feb 17, 2012 Posts: 530 Location: Del City, OK
Posted: Thu May 13, 2021 10:34 am Post subject:
Wes, I started with the Generator Output test per the pamphlet, I only get 1.4 volts at idle and 4 volts with the engine reved up. I did this test with only the adapter connected to the generator. Should I have the cable from the voltage regulator connected to the Adapter also.
IF is did this correctly the test procedure calls for me to replace the generator at this point.
I did not proceed to the rest of the tests in the series...
I am assuming the series of 5 tests is the full field test... correct with that in mind then I need to do the other 4 tests. _________________ Hal, KB1ZQ
TSGT, USAF (Ret)
1952 M-38 CDN CAR 52-31313
1952 M-100 Strick #104
1951 Willys Wagon (For Sale)
1954 Willys M38A1 201001205
Tornado Alley
Del City, OK
When you say adapter are you referring to the harness & conduit assy that attaches the regulator to the generator?
If you are not going to post a scan of the page you are referring to then perhaps you can offer us at least the page # and Paragraph #? _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Joined: Feb 17, 2012 Posts: 530 Location: Del City, OK
Posted: Thu May 13, 2021 10:57 am Post subject:
Page 12 of the test procedures - Generator Output Test _________________ Hal, KB1ZQ
TSGT, USAF (Ret)
1952 M-38 CDN CAR 52-31313
1952 M-100 Strick #104
1951 Willys Wagon (For Sale)
1954 Willys M38A1 201001205
Tornado Alley
Del City, OK
Joined: Feb 17, 2012 Posts: 530 Location: Del City, OK
Posted: Fri May 14, 2021 6:17 am Post subject:
Quote:
I connected my adapter to the generator output and started jeep. I did not connect the other end of the test cable to the voltage regulator.
So I need to connect the other side of the adapter to the voltage regulator to supply the voltage to the generator.
I am not using the military test set, I am using a digital voltmeter, You made a statement apply voltage to field side, looking at the procedure, I did not connect the two posts together...
I will rerun the test later today and go from there.
Thanks for the patience, been a long week, fixing minor problems and running against the clock... _________________ Hal, KB1ZQ
TSGT, USAF (Ret)
1952 M-38 CDN CAR 52-31313
1952 M-100 Strick #104
1951 Willys Wagon (For Sale)
1954 Willys M38A1 201001205
Tornado Alley
Del City, OK
Full fielding has a tendency to destroy voltage regulators. I always disconnect the generator to regulator harness cable/conduit so the armature output never gets to the regulator. The safe way to do a full field is this:
1 - Disconnect reg to gen harness at the generator. Grd your voltmeter to the generator frame. Clip your voltmeter Plus lead to the Armature pin A or C.
2 - Connect a jumper wire to the Fld pin B to the battery plus terminal on the starter. (the one that is always hot).
3 - Start the engine and do not race it. Never let the volt reading get above 45-50 volts. At idle the volts will be low, as you very slowly accelerate the engine the voltage should peak around 30-45 volts at about 1200 to 1600 RPM.
4 - shut it down and disconnect the jumper. If your voltage ran above 32 volts the generator is good and the problem lies elsewhere in your system.
That PM Magazine article is cute but only works with the military "Low Voltage Test Set" Stick to TM 9-1825B dated newer than 1947. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Joined: Feb 17, 2012 Posts: 530 Location: Del City, OK
Posted: Sat May 15, 2021 5:56 am Post subject:
With your comments about voltage regulators, I took mine out and gave it a good looking over, found a little bit of corrosion on the mounting points, cleaned that off and then hit the contacts on all 3 relays with some 600 grit sandpaper, very lightly mind you as I did not have the recommended crocus cloth.
I put the regulator back in and started the jeep. 24.xx V on the batteries before starting after I started it up they went to 27.5 V so it appears to be working fine now.
I am wondering if I kicked the circuit breaker in when I tried to jump my M-38 CDN as it was dead. 18 months sitting in storage will do that.
I am up and about this morning as I have the parade today and all. Hopefully it all goes well.
Thanks _________________ Hal, KB1ZQ
TSGT, USAF (Ret)
1952 M-38 CDN CAR 52-31313
1952 M-100 Strick #104
1951 Willys Wagon (For Sale)
1954 Willys M38A1 201001205
Tornado Alley
Del City, OK
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