jusplainwacky

On my 58...This one has me scratching my head. With the field wire disconnected to the voltage regulator, and with about 1500-2000rpm, my generator is outputting 31-32 amps. These were quick rev's so I don't burn things up. This is an indication of a shorted field in the generator. So I measure the field to ground and it's about 4.5-ohms...I really couldn't find what the resistance should be, but that seems reasonable to me.

So I remove my generator....connect up the armature "A" to the positive side of the batter and ground the casing...the generator spins...a couple of times it needed a little push to get it going. Then while it was spinning I touch the field with the battery cable and it immediately stops...all seems good.

SO I take the generator apart to inspect the inside...looking for maybe an intermittent short somewhere...no luck, but what I did notice is that the coating on the wires is starting to come off and the wires are getting exposed.

I was thinking maybe I'll take the coils out...seems simple enough...big screw....WRONG...I broke a screw driver trying to get them out...and no luck. Have an impact screw driver on order. I did shoot some WD-40 in around the screws inside and outside of the gen...letting it soak over night, but I have my doubts that is going to do ****. I was thinking if I can get the coils out, maybe I can buy some insulating paint/coating to go back over them. Or maybe just replace them...but can't see to find something I trust...like Ebay special from China. I searched CC and Pagagon….nada...I thought that was strange.

Actually this whole thing is strange....why the 100% output while the field is disconnected....and if anyone asks me what I get when I short the field to ground...please don't contribute to this post.

Suggestions anyone? Recommendations on a coating?

SDVette

How are you measuring the output of the generator?

65GGvert

I think at least one of you is talking volts instead of amps.

plaidside

Jusplain, there is a special tool to remove those field coils, it looks similar to an arbor press but with a large screw driver blade on the end of the arbor.
If the field circuit was shorted you would have gotten a zero reading on your ohmmeter.
When it was running did you disconnect the wire from the field terminal on the generator?
Joe

dplotkin

It is?

Generators don't output amps, they allow a given number of amps to flow unless sooner throttled by the regulator or throwing solder and quitting. A full fielded generator can make maybe 18 volts, so I am confused about the 31-32 amps you are measuring. But yes, a field coil shorted to ground will drive the generator to maximum output.

Since you have already removed and dismantled your generator let us know what happens when you get it back together. The generator must have field current to produce current in the armature, so this is about as simple a system as there is to diagnose.

Dan

jusplainwacky

Hi guys...thanks for contributing to my post.

Allow me to consolidate/answer your questions...yes the 32 amps is WAY too high and I certainly wouldn't run it for more than a split-second at that output.

How was I measuring the output...I have a very high-end FLUKE "camp" meter that can read voltage and amps (AC/DC).

In regards to this..... That is correct...and I was reading 4.5-ohms...that's the part that is making me scratch my head. However, if I had a resistive short or intermittent, it might go to zero when it's running (wires pumping current, expanding, and shorting out).
us
I called a generator rebuilder and they told me that resin (used with fiberglass) can be used to recoat the field wires. I mixed some up...put in on the coils...let it soak in...then waited until it started to thicken up and put that on top of the wires...came out nice. I also made sure that all the armature contacts weren't shorting out to the shaft...and all of them connected.

The thing is...I still haven't figured out why it was outputting as if the field was grounded...when it's not. I'm not seeing anything obvious. Tomorrow I'll stick it back in the car and try it again. I have a impact screw driver to get the screws off if it continues to output at max out when the field is disconnected...and yes, the car running.

dplotkin

If it was "outputting" as if the field was grounded, then you were measuring volts, not amps. To measure amps you have to put the meter in series with the circuit, to measure volts, in parallel, but based on what I've read you know that. So, the only thing that can be happening is that the field coils are shorted to ground. Has to be...there are no permanent magnets in a generator so the armature MUST have energized field coils to generate current.

Field coils are not expensive and are available. Before I gooed mine up with fiberglass resin I'd replace them, clean up the armature, replace the brushes and go for a ride. (Or let a rebuilder do it). I assume you are running these tests with the regulator disconnected and ruled out as a source of trouble, as in 80% of the cases in which a Genny quits, the trouble will be found in the regulator.

Dan

jusplainwacky

Thanks Dan for brainstorming...I agree that the reasonable conclusion is that the field is shorted...the thing that is perplexing is that when I go to measure it, it's not present and the only conclusion I can come up with is that it's shorting out when in use (running). And by the way...I am measuring amps....but not using the typical meter that goes in series...I'm using a FLUKE as shown below.
And I decided last night to bite the bullet and put in new field coils...might as well now that I have them out and if it is shoring out when under load, that can happen again.
If anyone knows where I can get QUALITY coils...let me know.

dplotkin

Inductive clamp. Very nice. That is what electricians use & it would need to be set to DC to work right in this instance.

Regardless, if you were indeed measuring 30 AMPS flowing from generator to battery with nothing sucking that sort of current (headlamps for example) than I don't understand what you measured. Except of course if you have a relatively new battery that has been discharged it will suck 30 AMPS out of a generator and level off as it reaches a charged state, maybe that is what you are seeing. When you full field a generator you will drive it to the maximum voltage it can make, but current draw is a function of a connected load. With the engine running, lights off and generator full fielded you would see something like 18 volts. What was the voltage output during this menagerie?

eBay has a bunch of field coils available. See https://www.ebay.com/itm/Delco-Start...-/190741025245

Rebuilders have a source for these that are hard for us end users to find. I would not use NOS coils with dried out funky insulation, which is likely the problem you are now having.

Dan

domenic tallarita

I'll stick my neck out on this one! This is a (do not try @ home one) If you don't have that special tool to remove the screw, I did it this way and it worked. Now my screw driver is about 2 feet tall and fits the screw perfectly. Can't use propane and need to get in & out fast. Need a welding tourch and candle wax. use a big tip and heat the screw red hot. Should take only a few seconds. Put the candle wax around the screw and expect a flame. The screw wont transfer enough heat to the metal block that the wires are wound on. Then assuming that the generator is being held in place use a wrench to turn the screw driver while pushing it down as hard as you can and twist. Then have a wet rag handy and cool the screw. The heat expands the screw and creates a small distance between the threads and the case allowing the wax to wick in the threads.
In the 60's I worked in a rewind shop and we would put the coils in a oven after a wash in a mild solvent, then dip them in varnish and let them soak. Then back in the oven to bake the varnish. while the varnish was hot it would scrape off the metal easily, then harden. If it hardens then we removed the varnish with a hand air grinder. That was called a bake out and insulate on the work order. There was also a epoxy that was green that was used if it was to be done cold after it was washed in mineral spirits and baked out till dry. It was done much like you described.
I'll back up a bit here. the tourch will not turn the case red if you center it on the screw. The threads cause a bridge that causes the heat to stay mainly on the screw. Again you have to get in & out with the tourch in a matter of seconds. A propane tourch won't do any thing but damage.

Dom

SDVette

Does the ammeter in the car agree? +30 amps?

jusplainwacky

I guess it would be a good time to tell you that I'm an electronic engineer....and have considered all that you have stated. I even removed my voltage regulator and manually depressed the Current and Voltage coils which open the field circuit to ground and feeds the field through a resistor to ground which limits the generator output based on this resistor. One of the perks of being an engineer is that I have good equipment.
To answer you question...there was no "load" on the generator other than the battery which is in good shape and measuring 12.65volts.

jusplainwacky

yes

jusplainwacky

I have an impact screw driver that apparently will get these screws out...if that doesn't work and it seems like it will be a hassle to get off...I may just stick it back in and see if my cheap solution works. AND drive the car around for some weeks to see if it lasts. It wasn't that hard to get out of the car.

Mark Lovejoy

If the meter pictured is the one you are using for your tests I see a problem with your approach.

That meter doesn't measure DC amps only AC.

jusplainwacky

Good catch...but it doesn't apply here. FLUKE makes many clamp meters...mine reads DC Amps.. I just quickly found a picture of a claim meter as an example. Here is mine. DC amps is at the 12'o-clock position

SDVette

(that's why I asked if the in-car meter agreed)

Seems like all your logic is sound and you have the issue isolated.. Let us know what happens!

dplotkin

Yes, but that explains a lot. You want to understand the underlying electrical phenomenon, The rest of us would be happy with an operational charging system. Put new field coils in it, a set of brushes, bearings and a inspection of the regulator contacts. Forcing the contacts closed on either regulator element will burn the contacts and is never advisable. Most charging circuit trouble will be found in the regulator. Any original unit is by now worn out and the replacement units are nowhere near as good as the originals. I find they last 5 years tops, have one giving me trouble right now on my 63.5 Galaxie.

Dan

jusplainwacky

LOL Dan...I'm sure you are right!!

dcamick