Watching my ammeter swing to “D” and never to “C” started me digging into my charging system. I have a Series 1 3.8L positive ground with the C42 Generator and the RB340 Current Voltage Controller. Long story short I went online and could not get any of the recommended testing to work so I pulled the Generator out of the Jag.
One last test - jumper it up and see if you can run the generator like a motor - and it worked!
Test described here from Moss Motors:
I was happy to see it move but I wanted something more quantifiable with my voltmeter. I pulled out the RB340 Current Voltage Controller from the Jag and setup a bench test with Generator, the Controller, a spare Battery and a drill to turn the generator up to 2500RPM.
Still no matter which test I ran I could not get 14+Volts on my meter when spinning the Generator (clockwise).
Is it the Generator? Can’t be it rotated like a motor.
Is it the Controller? It looks brand new inside and out. (I also made sure to polarize it)
I must be doing something wrong. Thoughts?
The Negative Part - I want to go get the Dynalite/Alternator and call it quits.
The Positive Part - I have learned more about Generators, Alternators and Controllers than I thought imaginable - just not enough to fix the problem.
Aren’t there several generator tests in the manual which isolate the generator? Mine dropped to zero V about five years ago and by going though those tests I isolated it to a bad coil. Assuming your drill will go fast enough I see no reason you couldn’t bench test it that way.
I will read through the manual again and see if I can conduct some of the tests listed. I just assumed if I could get it to spin like a motor, the field coils and armature had to be working, but maybe they are not in good enough condition to produce a fully operational charging system.
What did you do when you learned you had a bad coil? Send it out for repair or switch over to an alternator?
It looks like all the usual’s are selling the Dynalite C42 Alternator and now they even make a dummy “controller box” which allows you to make all the electrical connections the same way as orignal. I was wondering if people are moving in that direction?
I had a spare parts generator that had a good one to swap. Yes many have switched to the alternator drop ins or just an alternator with a custom bracket. Parts are getting a lot harder to find for the dynamos nowadays.
Bob, yes it can. Typically there is enough residual magnetism in the fields that simply connecting the armature to the battery will cause it to “motor.” Once it is motoring, then you need to connect and disconnect the field wire to see if the “motoring” changes. But what I see you have hooked up on the bench is the generator and voltage regulator. You need to confirm the generator alone first. (In the future, I always suggest troubleshooting on the car with an engine big enough to power the generator and all the car wiring so it can be troubleshot at the same time. Your drill should be adequate for what you are doing, but it probably would not be large enough to do a full load test of the system.)
Tom
Thanks for the feedback Tom. Is there a good stand alone generator test I can conduct? My understanding is the Generator outputs AC so a DC voltmeter is not a good method - but that could be wrong.
The generator will output DC and your DC voltmeter will work. My method is to typically connect the Generator to the battery, taking into account the proper polarity. I assume positive ground, so battery positive to generator frame, battery negative to generator D output. At this point, you will get a strong spark and the generator will probably start to spin if the drill were not holding it back. Do not leave it sitting this way- it is a short. I would then turn on the drill and then when you connect the F to the D to energize the fields, your volt meter across the battery should climb relative to drill speed. If this occurs, your generator is almost certainly good. The next test would be to load it and see if it will output the rated amps, but that is not typically necessary. Usually if it charges it is good.
Oh, and the current that is actually in the armature is AC, but the commutator converts it to DC, so that is all you will see- DC.
Tom
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FYI - Jerry Mouton, after several C40 failures, put in one of those alternator-that-looks-like-a-generator thingies. It was no better. IIRC, the first one failed quite soon got replaced. The replacement failed as well. I seem to recall shortly before he passed away, he told me he was planning to put the C40 back in.
My earliest car had a generator and it’s regulatory function was simple. A cut out. A coil that closed on power creation and opened when there was none. A gate or one way switch. Next two or three, same.
Vaguely I recall a two coil Regulator. In a can. One as the cutout and the other for either volts or amps A bit fuzzy there.
And my mentor and college part time job employer taught me a bit about the contemporary three coil regulator. He had a device to measure out put and the means to regulate it by altering spring pressure.
My early bench tests were simple. Apply volts, if the generator motored, it was declared good.
My school chums circa a 1948 built a GP trailer that included camping functions. Tarped gear and a generator for lighting!!! Simple, A one coil generator powered by a 3 HP or so Briggs and Stratton engine.
A sealed beam or two for lights or so . Usually cast off units with one filament remaining . for fun, an ammeter was in the circuit…Never made up the planned wires to charge another battery. Our cars were wont to “dead” batteries. Never new, just junk yard sourced…
Student jobs not that remunerative…
So I connected the battery positive to frame, battery negative to generator D and jumper from generator D to F. Voltmeter was connected across the battery. The Generator began to motor and then I kicked in the drill to get it up to speed ~2000RPM. No change at the voltmeter
Still surprised the Generator can motor but not put out a voltage - seems strange.
Bob, assuming I understand all that you did, it sounds as if the fields are bad in the generator. The declaration that a generator that motors is good is only half true. Most generators fail because of faulty brushes. If the brushes are bad, it will not motor. But, because of residual magnetism, if the armature and brushes are good it will motor even if the fields are shot. Since yours will not generate, but it will motor, it appears the field circuit is shot (or we are not doing the test correctly.) From the manual, they instruct us to connect the D to the F post to check, so I assume the other end of the fields is connected to the frame internally. Next, I would check with an ohm meter from the F post to the frame and see if you have very low resistance. It sounds as if that circuit is open. There are two ways to wire the fields. The manual indicates the one end of the fields on yours is to the frame. But the other method is to connect the other end to the armature post. You may want also check for continuity there, but because of the armature circuit, you may not get a good reading. If the fields are open, I would consider opening up the generator and check the connections.
Also, you may want to check as if the generator was wired the opposite method. Simply connect the D circuit as before, but this time, instead of jumping the F to the D, jump the F to the frame.
Tom
Hi Ray,
He did put the C40 back in before the 2017 Oil Leak but then when his son was driving back to California after Jerry died the C40 stopped working again. His son reinstalled the ‘Genernator’ and he got it home.
When I got the car back to Boise I realized that the VR was still in the circuit which accounted for the very twitchy amp meter readings while I was driving MIK to his new home. I have the generator now at the local Auto Electrical shop to be checked and if possible rebuilt assuming that they don’t forget about it with the social distancing stuff that’s going on.
I still can’t figure out why Jerry had such bad luck with generators, I guess I have similar luck with fuel pumps so it shouldn’t really surprise me.
Cheers,
LLynn
You might want to open the regulator and see if it’s an original relay type. Jerry at one point picked up a SS regulator from I think, Clover? I bought one as well, and within about 50 miles my generator field could burned out. Correlation may not equal causation, but that regulator is no longer in my car. I’m fresh out of spare field coils with which to test the theory.
It just wasn’t an Oil Leak Tour without having to swap out his generator at least once!