Help With Generator Cutout

S

sellerby

Member
I have attached a photo of the generator cutout on my 30 Tudor. I would appreciate hearing from any who can ID the Standard Motor Products cutout and tell me whether this was a common replacement and the general time frame it was sold and used.

Also, and more importantly, one of the wires to my ammeter got hot enough to burn the insulation and damage the ammeter, which permanently registers a 10 on the discharge side of the scale whether the motor is running or not, and whether the battery is disengaged or not. I replaced the entire loom between the terminal box and the instrument panel, and I added a fuse to avoid a similar problem. However, I wonder whether the generator cutout may have played a role.

Could any explain how I can use a multimeter to test the ammeter? I am not electrically-inclined, so I would need very basic instructions. I tried to use the multimeter while the engine was running by touching the black lead to the screw on one side of the cutout and the red lead to the screw on the other side, with the multimeter set to read between 3 and 10 volts. Nothing showed on the meter. I then switched the leads to the opposite screws, and still nothing showed.

The car runs well now that I've added the fuse and replaced the instrument wire loom. But I would like to make sure that the generator cutout is doing what it is designed to do. It also might make sense to replace the cutout with something that looks a little more stock. Is the diode replacement a wise choice?
 

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If the ammeter is stuck, I would replace the ammeter. With a working ammeter, you could more easily tell what your cutout is doing.
 
The red lead on the meter goes to ground, like a head stud or the cut out base.
With the engine off put the black lead on the rear terminal of the cut out and you
should have 0 volts, put it on the front terminal and you should have battery voltage.
with the engine running at fast idle you should have about 6.5 to 7.0 volts at
both terminals.
 
Thanks MC and Bob! I definitely plan to replace the ammeter, but I'll give a try to Bob's suggestion on testing the cutout. I'd rather order the new cutout with the ammeter if needed.

I've never seen another cutout like the one on my generator. It looks old, so I'm guessing was a replacement part in the 30s or 40s.

Best regards,
 
Lorenzo said:
Where is Tom W when we need him?
Click to expand...

Look at the time. He's sleeping.:D

I suspect that cutout was made as late as the 50's or 60's.

You made the right check when you set the volt meter on low DC volts and checked across the two cutout terminals for a voltage drop. You showed 0 volts, which is good and means the contacts had a good connection while the car is running. Doing the same check with the engine off, you should show battery voltage, because the contacts should be open.

Testing as Bob mentioned is also another good way to check the cutout function, plus it checks the generator for output.
 
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AmmeterTool1.jpg


AmpGuage-1.jpg


If your ammeter is an original, I'd try to fix it and use it rather than install a repro. The original fits the hole and works better than repro's. To test an ammeter you need a good quality ammeter and connect it in series with the Model A ammeter. Then run some current through them, such as turning on the headlights. If that draw is 9 amps on the known quality meter, then it should also show 9 amps on the Model A ammeter. Menards sells a good multimeter for $20 that has a 20 amp scale. It's a Sperry SP-152A.

I like to put a drop of very heavy oil, or thin grease on each of the two pivot points for the ammeter.

As Mike noted, the generators with a rubber grommet and wires coming out of the case were built after the Model A's.
 
Boy, now I learn that I have more "non-standard" parts on my A! First it's the diamond engine, and now my generator is also out of judging standards. Looks like some more work before I start winning the competitions.

I'll order the new ammeter and try Tom's suggestion of wiring it in series with the one I now have. I'll also try taking it apart per Tom's photo and lubricate it. I think that, at least, it is original equipment.

Thanks as usual!
 
Patrick L. said:
Your little 'nut driver' looks nice, pretty slick..
Click to expand...

Thanks Pat. I had an aluminum knob from something and figured it would make a nice handle for my tool. Since I don't have any more knobs I have made and sold a few tools like shown below. This is actually better, because it won't roll off the table edge, and will lay flat in the tool box.

AmmeterTool4.jpg
 
Sellerby, the needle is very thin aluminum and may have been knocked off center by the sudden ******* from a short. It's delicate, but can easily be bent back to center on the "0" mark. I find a restored original guage to be quite accurate, but the main reason to look at the guage is to see if you left something on, or have a stuck brake light switch, etc.
 
I also solder the carriage bolts to the meter shunt. Then if the nuts get a little loose you have less chance of arcing at the connection.
 
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