Cutout Bad? Can I run without it?

[DesertMike]

Hi All,

I’m a total Model A newby helping out with a friends estate. This is a ‘30 Model A Pickup. It has a massive discharge showing on the ammeter and drains the battery pronto.

After a little checking I believe the cutout has failed. The battery connection at the cutout gets real hot and disconnecting that eliminates the discharge.

I dissembled the cutout hoping it might just be stuck, but find it has some sort of diode installed. I assume the circuit should be open with no power to it
, this one shows resistance across the terminals all the time.

Can I operate the vehicle with the cutout disconnected understanding it won’t charge the battery? I’ll find a new cutout or one of the diode conversions.

Thanks for any advice.

[Bob C]

No you can't run without the cutout, you will damage the generator if it is disconnected
from the battery. Any chance the battery is connected with the negative to ground
as the Model A is positive ground.

[DesertMike]

Well, great question. The battery was installed negative ground at some point. The truck runs, I never considered that a possibility.

I’ll swap the cable connections, and see what happens with the cutout.

I believe this may have been a long-standing issue. There is a master battery disconnect switch installed and I’m sure that is not original.

[DesertMike]

Good news. Swapping the battery to positive ground has stopped the battery drain.
Connection at cutout is no longer warm to touch.
It isn’t charging, so that will take a little more diagnosis.

Thank you for the help

[TerryO]

You may need to polarize the generator.


TOB

[redmodelt]

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Yes you can run without a cutout but you have to ground output wire/post coming out of the generator to the frame/engine or something.

[rotorwrench]

A diode will pass current one direction only if it's good. An Ohm meter can be used to check it. It will have continuity with test probes connected in proper polarity but no continuity with reverse polarity.

I would first make certain that all wiring in the charging circuit is clean and tight. Make sure the battery voltage is 6-volts. Repolarize the generator field pole shoes to positive ground for sure if it was run in reverse polarity for any length of time.

The surest way to get it polarized is to remove the brush cover strap and find the 3rd movable brush. Connect a jumper lead to the wire attached to the 3rd brush then touch the other end to the starter switch post (connects to negative post on battery). Do this momentarily. It only takes a quick jolt from the battery to remagnitize the pole shoes. The other end of the field is already connected to ground on the generator case. Just be careful not to touch the power jumper to any ground surfaces.

[Badpuppy]

Someone may have set up the AA for negative ground, with a diode cutout, which must be of the correct polarity. Installing a battery with positive ground would result in what you describe.

Converting back to positive ground would require replacing the cutout for positive ground.

Most polarity conversions are for running at 12V as well. Check your light bulbs to see if that's the case. You can run the car with either polarity no problem, but you may find it easier to just swap in a 12V battery, negative grounded, depending on what you find.

Edit: I reread your post, battery grounded positive stopped the discharging. Seems your cutout is for positive ground. Appears to be a generator issue, polarizing may fix it. Also, you need about 1200 rpm to show a charge.

[DesertMike]

Thanks to all for the advice and suggestions.

I got to the 3rd generator brush and was successful re-polarizing the generator. It's now charging at 7-9 volts and about zero with the lights on.

I never was able to get any current readings across the cutout, so i'm not sure of the situation there, but it's charging while running and not discharging when off so maybe we are good to go!

[rotorwrench]

With those results, it sounds like it's working. You mention volts. What does the amp meter tell you?

[DesertMike]

The ammeter is reading about 10 at a fast idle, drops to around zero with high beams on.

[Bob Bidonde]

You can run with a bad cutout, but there are conditions. I do recommend that you do not make a habit of doing this. See the slides:

[johnbuckley]

Originally Posted by Bob Bidonde

You can run with a bad cutout, but there are conditions. I do recommend that you make a habit of doing this. See the slides:

... lovely pics and clear directions Bob!

[Bob Bidonde]

Thanks for your comment John. I did however goof when I noted, "...that you make a habit of doing this." I have edited my post to read, "..... do not make a habit of doing this" regarding running with a failed cutout or without a cutout.

[rotorwrench]

I agree on that last red statement in post 14. It could be sacrificial on the generator to run it too long with no battery connection but I have realized the need to get to a better stopping point than way out in the toolies with limited resources at hand. A lot depends on how much it will generate on residual magnetism and how hot it may get with the cut out open. With a dead battery, it could get pretty hot if the cut out is on line.

[johnbuckley]

so what are the symptoms that might indicate A) cutout stuck open B) cutout stuck closed. ( not so easy without an ignition warning light!)

[rotorwrench]

Stuck open will show discharge while running with a strong battery. Stuck closed will work as long as the engine is running. It will show a big discharge after the engine is shut down due to the generator trying to motor. The battery and the generator will suffer if it sets too long like this.