The Ford Barn

Zephyr4 · 02-02-2019, 10:11 AM

I have a 31 model A generator that isn't generating. The car has been in a barn for decades and the generator has never worked for me. I suspect all kinds of issues within the generator itself, but thought I'd start with the cutout.

I followed the "Restorer's Model A Shop Manual" by Jim Schild. The heavy coil read zero resistance and the fine coil 51 ohms. Good according to the book. I manually operated the armature and found that the contacts didn't contact. So I undid the two screws and closed the gap to .015". Now they would make contact. While I was at it, I cleaned the contacts. The book says the contact points should have a clearance of 0.015" to 0.020", so that's good.

It then says the "core gap should be 0.10 with the contact points closed." Is this the gap between the armature and the iron core? If it is, then I have 0.010" with the points open and pretty much 0 with them closed. How do I adjust that one?

The book next says that connecting a trickle charger or battery across the base and generator terminal should cause the points to close. I used a variable power supply and dialed up 6v. Nothing happened. I manually operated the points and found they would stay closed until I disconnected the power. So I wound up the voltage and found the points close at a tad over 8v.

I've read this page http://modelabasics.com/Cutout.htm and found it very helpful too. I'm guessing Schild's "core gap" is the "air gap" on this page.

So here's my uncertainty:

1) The air/core gap should be 0.010" with the points closed? Can anyone reassure me on that one? To adjust, do I loosen the two screws that go through the spring retainer? The exploded diagram on the webpage shows circular holes, nothing slotted, implying no adjustment that way.

2) The webpage says 6.1 to 6.3 volts should be enough to close the points, but that's on the generator with the engine running. I'm doing a bench test, so does the 6.1 to 6.3 volts still hold true?

Any advice would be greatly welcome. I'm aware I can easily fix this with a diode conversion, but I'm a sucker for punishment.

Apologies if this has been covered before, I did search to forum for it but didn't quite get what I was looking for.

02-02-2019, 10:11 AM	#1
Zephyr4 Member Join Date: Sep 2017 Location: Banbury, England Posts: 35	Bench testing a generator cutout I have a 31 model A generator that isn't generating. The car has been in a barn for decades and the generator has never worked for me. I suspect all kinds of issues within the generator itself, but thought I'd start with the cutout. I followed the "Restorer's Model A Shop Manual" by Jim Schild. The heavy coil read zero resistance and the fine coil 51 ohms. Good according to the book. I manually operated the armature and found that the contacts didn't contact. So I undid the two screws and closed the gap to .015". Now they would make contact. While I was at it, I cleaned the contacts. The book says the contact points should have a clearance of 0.015" to 0.020", so that's good. It then says the "core gap should be 0.10 with the contact points closed." Is this the gap between the armature and the iron core? If it is, then I have 0.010" with the points open and pretty much 0 with them closed. How do I adjust that one? The book next says that connecting a trickle charger or battery across the base and generator terminal should cause the points to close. I used a variable power supply and dialed up 6v. Nothing happened. I manually operated the points and found they would stay closed until I disconnected the power. So I wound up the voltage and found the points close at a tad over 8v. I've read this page http://modelabasics.com/Cutout.htm and found it very helpful too. I'm guessing Schild's "core gap" is the "air gap" on this page. So here's my uncertainty: 1) The air/core gap should be 0.010" with the points closed? Can anyone reassure me on that one? To adjust, do I loosen the two screws that go through the spring retainer? The exploded diagram on the webpage shows circular holes, nothing slotted, implying no adjustment that way. 2) The webpage says 6.1 to 6.3 volts should be enough to close the points, but that's on the generator with the engine running. I'm doing a bench test, so does the 6.1 to 6.3 volts still hold true? Any advice would be greatly welcome. I'm aware I can easily fix this with a diode conversion, but I'm a sucker for punishment. Apologies if this has been covered before, I did search to forum for it but didn't quite get what I was looking for.