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Farmall & IHC Tractors Discussion Forum
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1940's Farmall H - Replacing Light Switch

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Brian

05-19-2004 09:23:29




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I am restoring my father's late 40's Farmall H and I need to replace the light switch. The old switch operates the generator and the lights. The IH replacement is just a light switch.

The dealer did not have a service update on how to wire the generator to function properly, i.e. high and low charge, only that they sometimes put a resistor in the generator circuit in line with the GEN F terminal. Does anyone have a service update or details on rewiring and splitting the generator circuit out from the original to operate with the replacement light switch?

I have a 6V system with a cutout. I have replaced all the wiring and had the generator rebuilt, and polarized, and cutout checked. I can obtain full generator output by "shorting" the Gen F terminal to the chassis, but I don't know what components and values the original switch had. (I have verifed the wiring with the stock H 6 volt generator w/cutout relay/distributor ignition and it matches, but the unit did charge with the old switch.)

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Dave S.

05-19-2004 19:39:48




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 Re: 1940's Farmall H - Replacing Light Switch in reply to Brian, 05-19-2004 09:23:29  
I have a 45 H with the cutout relay system. On the back of the switch there should be a rectangular piece of formica with a resistor wire wraped around it and the ends of the wire connected to two screws this is the resistor for high and low charge. If this is missing or burned into it will not work on low charge but should still work on high. Also make sure that the switch has a good ground to the case and the case to the steering pedestal or it will not work on high or low charge. The ground is often the problem.

Don't mistake the chargeing resistor with the coiled resistor wire at the top side of the switch, this is for the bright and dim lights.
The CIH dealer said the resistor or the original switch was no longer available. I bought a used one out of a salvage yard. The switches ought to be easy to come by but a good charging resistor may not be. Good luck

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CNKS

05-19-2004 18:51:40




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 Re: 1940's Farmall H - Replacing Light Switch in reply to Brian, 05-19-2004 09:23:29  
No one has mentioned this, but if your switch is the same as came on the tractors when new, I think it can be wired for four positions. In other words there is only one switch, just put together different, depending on whether there is a cutout or regulator. But, you have to take the thing apart. On the C I bought a while back mud daubers glop filled the whole light box. The C had a regulator so the switch had 3 positions. I tossed the wiring and disassembled the switch. Put it together wrong and had four positions. Took me a couple of hours to get it back together right so that the lights were wired right along with having the 3 positions. I am not sure this will give you LHDB, but if you want to mess around with it, you might give it a try. You will probably need the diagram that is in your operator's manual. I did not start the tractor until I had the switch correct, though, so I don't know what the extra position would have done to my regulator.

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Bill Smith

05-19-2004 12:04:45




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 Re: 1940's Farmall H - Replacing Light Switch in reply to Brian, 05-19-2004 09:23:29  
I agree, either put on a regulator replacing the cut out with the new light switch, or find a 4 way switch and keep the cut out. Remember that the system was originally positive ground (ground cable hooked up to positive battery post). Make sure you wire correctly and polarize correctly.



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Bob M

05-19-2004 10:40:09




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 Re: 1940's Farmall H - Replacing Light Switch in reply to Brian, 05-19-2004 09:23:29  
Brian - Probably the easiest solution is to replace the cutout with a voltage regulator. Then the charging system will operate completely independently of the light switch. Incidentally it is also best for the battery. (A regulator does a much better job of matching generator output to the battery's charging needs than can the average operator!)

Figure $35 - $40 for a regulator. Wiring is straightforward (punch below for a diagram.) ...Bob M

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Brian

05-21-2004 08:26:16




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 Re: Re: 1940's Farmall H - Replacing Light Switch in reply to Bob M, 05-19-2004 10:40:09  
Thanks, It looks like the regulator is the way to go.



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riverbend

05-19-2004 18:00:16




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 Re: Re: 1940's Farmall H - Replacing Light Switch in reply to Bob M, 05-19-2004 10:40:09  
Is it possible to connect a voltage regulator to act like a cutout ? I'm pretty sure that I have a regulator on my H (that's what I bought), and I have the 4 way switch. When I go from H to L the charging rate drops off. One more complication, when I was trying to sort out the wiring originally, it looked like a mixture of the distributor wiring and the mag wiring as shown in the operator's manual.

Thanks

Greg

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Bob M

05-20-2004 04:25:16




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 Re: Re: Re: 1940's Farmall H - Replacing Light Swi in reply to riverbend, 05-19-2004 18:00:16  
That's definitely possible! It means the generator is wired up incorrectly.

Sounds like your H has the gen "F" terminal wired to the field resistor on the light switch. Instead the gen "F" terminal should connect to the "FLD" terminal at the regulator.

If you reconnect as above the generator should function properly - presuming the regulator is good of course.



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Red Dave

05-19-2004 10:32:07




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 Re: 1940's Farmall H - Replacing Light Switch in reply to Brian, 05-19-2004 09:23:29  
I see two possible solutions,
Get the right switch or replace the cutout with a regulator.
The right replacement switch should be available, if not from a Case/IH dealer, then maybe one of the aftermarket distributors should have one.

If you put a regulator on it, you won't have to remember what charge level you want to be at. Less chance of over/under charging the battery.

Maybe C&G would have the right switch, 608-455-2411

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Brian

05-21-2004 08:23:26




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 Re: Re: 1940's Farmall H - Replacing Light Switch in reply to Red Dave, 05-19-2004 10:32:07  
Thanks. It looks like updating to a regulator is the way to go.



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