Bad generator?

[JayJay]

Folks, could use your help double-checking my logic.


The vehicle: 1930 pickup, full resto 1980, driven <1000 miles over the 40 years, I bought it in Feb 2020. Don't know much about the history other than the restorer was a body guy and I have not been too impressed with mechanical/electrical that I've seen so far. It seems to be pretty original, painted over.



Anyhow - I'm driving it regularly, used to seeing around +12A at road speed. Yesterday I was driving and saw that it was sitting hard on 0 amps. Got the usual dip to negative amps with stoplights, headlights, etc.


My first thought was "stuck cutout relay", knowing that the cutout needs to close to allow the generator to charge the battery. Whacked it upside the head to see if that worked, but of course it didn't.



Second thought was "fan belt tension". No indication of slippage (noise, rubber chips, etc.) but it was a bit loose, so I tightened it. No change.


Got to looking more today. What puzzles me is that output voltage of the generator, with our without the cutout in the system, is ~1.5-2V. Shouldn't I be seeing 6V or so at the output of the generator/input to the cutout? From my understanding, moving the third brush would not change output voltage, only amperage, right? (I haven't touched that yet).


I have no particular issue with rebuilding or replacing the generator, but I'd like to feel more confident that I've got a good chance of licking it.


Thanks in advance. Stay healthy.


JayJay

[GRutter]

Check to see if your generator will "motor".
You can do this with the generator in the vehicle.

1. Release tension / remove the fan belt from the generator pulley
2. Jump the two terminals on the cutout. One side of the cutout is connected to battery, the other side to the third (adjustable) brush in the generator.
3. The generator should "motor", and turn in the same direction it would when driven by the engine.

If it motors, it should also generate. If not, you may have bad brushes or field windings.

[ryanheacox]

If it doesn’t motor check to see if you have a brush hanging up. Might be as simple as that.

[JayJay]

Thanks, gentlemen. I'll try both of those (never even thought of a hanging brush, DOH!)


Lovely pickup you show, GRutter. Guess I'd better get a pic of mine up.


Best wishes.


JayJay

[30 Closed Cab PU]

Originally Posted by ryanheacox

If it doesn’t motor check to see if you have a brush hanging up. Might be as simple as that.

X2, happened to me. Intermittently no charge. For me was the 3rd brush. sprayed minimal wd40 on the pivot and spring, exercised the brush, then added minimal light oil and exercised the brush - issue solved.

[GRutter]

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Generator Cutouts normally stick closed. If that happened, the battery would have tried to discharge back through the generator, and may have damaged the windings.

While you're looking at your charging circuit, you might want to consider a diode cutout to replace the original. Be sure to order one for the voltage and polarity of your car. I am assuming you're vehicle is original at 6v and Positive Ground.

If your generator was only putting out 1.5 to 2 volts, I would suspect field windings, but do check that all of the brushes have spring tension against the commutator.

[30 Closed Cab PU]

I think when the cutoff contacts are stuck closed the Ammeter would show a discharge with the ignition off.

[Will N]

Also try cleaning the commutator.

[Bob C]

When you get it charging I would cut back on the charge rate, 12 amps
is to much.

[Purdy Swoft]

If the starter doesn't drag with the switch off but drags and bucks with the switch on the problem will usually be timing is too advanced . Too much gap at the points will have an advancing effect . Ford specs for points gap is anywhere from eighteen to twenty two thousands . The spark happens when the points begin to open . Too much gap causes the ignition timing to be too advanced .

[JayJay]

Most excellent, thanks all. Yeah, I know +12A is too high (although that's what the original Ford recommendation was) but between getting the headlights working, sorting out taillights, replacing broken crank pulley, ungumming the radiator, etc. etc. I just haven't gotten around to backing that off. I do plan on replacing the cutout with a diode cutout, too.


Will dive into this more today after escorting the bride shopping.


JayJay

[katy]

I do plan on replacing the cutout with a diode cutout, too.

Pull the cover off the cutout to verify what you have.

[Purdy Swoft]

Try a Fun Projects voltage regulator if you can find one .

[JayJay]

Well, another day into this and I'm throwing in the towel for now. I pulled the generator, took it apart and cleaned everything up including polishing the commutator. Checked continuity through the field magnets - good (but I didn't separate them from the case, so I suppose there could be an intermediate short to ground that I didn't pick up). I did find one dead pole on the commutator but otherwise OK. Put it back on and yea, the generator motors, and I'm back getting 12A at motor speed. So I tried moving the third brush to adjust that and - no significant change from one end of its adjustment to another.



Well, dang. Then I remembered that when I took it apart the third brush was connected to the cutout input, not the field magnet as it's supposed to be. So I swapped out the fixed brush and the movable brush connections, reassembled, checked for motoring (yup) and fired it up. Well, back to no charging. Curiously, voltage output at the cutout varies from zero to around 4.5.


It's pretty clear that someone has been into this generator in the past, as there's one brush holder that is different from the other two. Also, there are two brushes of one brand and one of another. What I'm thinking is that somewhere along the line someone previous to me ran into this same problem, and figured out that by swapping the two brushes it would essentially take the third brush varying amperage out of the circuit and get charging, although you could not regulate it. Just dumb luck you ended up with 12A, which is not so far from tolerable that they let it go.


I'm not seeing how a bad cutout would show up as the bizarre voltage input into the cutout. Anyone have any ideas? I'm about ready to say to heck with it, order an alternator and put the generator on a back shelf until after I retire and can deal with it.


Thanks for all your help, folks.


JayJay

[J Franklin]

You could take the generator off and to a shop for testing.

[Bob C]

[QUOTE=JayJay;1937989]Most excellent, thanks all. Yeah, I know +12A is too high (although that's what the original Ford recommendation was) but between getting the headlights working, sorting out taillights, replacing broken crank pulley, ungumming the radiator, etc. etc. I just haven't gotten around to backing that off. I do plan on replacing the cutout with a diode cutout, too.


Attachment from the owners manual.

[30 Closed Cab PU]

If you like to leave the battery in your car during storage, be aware diodes have a slight leakage current and given enough time can discharge the battery. Use a maintainer, or disconnect the battery, or disconnect the diode cutout. Happened to me when one winter I forgot to put on a maintainer.

[katy]

be aware diodes have a slight leakage current

A GOOD diode doesn't "leak", unless its subject to voltages higher that it's PIV (peak inverse voltage) rating which can destroy it if high enough.

[30 Closed Cab PU]

Originally Posted by katy

A GOOD diode doesn't "leak", unless its subject to voltages higher that it's PIV (peak inverse voltage) rating which can destroy it if high enough.

Most all diodes leak, even within rated specs. Good diodes leak very little current. I admit that I might have a marginal diode, but it is still possible you may not know you have an abnormally leaky diode until the battery goes bad during a long storage period.

https://en.wikipedia.org/wiki/Reverse_leakage_current

https://electromaniaweb.wordpress.co...nt-in-a-diode/

[JayJay]

[QUOTE=Bob C;1938192]

Originally Posted by JayJay

Most excellent, thanks all. Yeah, I know +12A is too high (although that's what the original Ford recommendation was) but between getting the headlights working, sorting out taillights, replacing broken crank pulley, ungumming the radiator, etc. etc. I just haven't gotten around to backing that off. I do plan on replacing the cutout with a diode cutout, too.


Attachment from the owners manual.

*****
Thanks, Bob. Service Bulletin recommendations from Ford are all over the place - 9(1) January 1928 says 14A winter/10A summer; 9(12) November 1928 suggests 10A @ 1500 rpm for "cold" weather; 10(5) for May 1929 suggests 6A for summer, and like you said the 1930 Owner's Manual says 10A winter/6A summer. And general consensus nowadays seems to be that all of these are relatively high for current practice. Not quite sure where I got 12A in my head, but regardless, this generator isn't going to get below 12A unless it's zero.


My cutout is pretty sure not original, it's quite light and has "batt" stamped on the output terminal, which I don't think is original. And the top is crooked and held on with a couple of crimps only - pretty cheap feeling all around. I'll open it up to see what's inside and if it's a real cutout (not a diode) I may try flashing the coils to see what happens. Nothing to lose at this point.


Every day a challenge. I don't remember these things from 50 years ago when I had my last Model A but perhaps that's just time erasing bad memories.



JayJay