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I have a model 40 that I recently picked up it was converted from 6 volts to 12 volts. The wiring is a mess and I have started to update wiring. The hour meter was not connected, I am wondering will the hour meter run off of 12 volts and if not is that why it was not connected, any help would be appreciated. This is my first tractor rebuild.
 

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I wouldn't apply the higher voltage without doing some detective work. You don't want to burn open the meter. Finding out the internal resistance of the meter and the voltage applied to it under the 6 volt system would be a good start. You can't even assume that six volts was applied to it under the old 6volt system. There might have been shunts or series drop resistors in the circuit.
 

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Don't know for sure but I would expect the stock hour meter to be in the tach. The only electricity to it would be a light.


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Not exactly an answer to your hour meter question, but on the topic of 6v to 12v conversions; In my experience, it is easier to completely remove the rats nest of old wiring and start over rather than to try to replace it piece by piece. A wiring diagram helps. A 12v conversion is more than just changing the light bulbs because you need physically more wire to carry the additional current.
 

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Not exactly an answer to your hour meter question, but on the topic of 6v to 12v conversions; In my experience, it is easier to completely remove the rats nest of old wiring and start over rather than to try to replace it piece by piece. A wiring diagram helps. A 12v conversion is more than just changing the light bulbs because you need physically more wire to carry the additional current.
Actually 12v systems use less current than a 6v due to twice the voltage. So the wiring for a 6v system is more than adequate size wise for the accessories on the tractor. The condition of the harness may dictate replacement as you said. It's fairly cheap and easy to do. One of the issues is the generator. I'm replacing the generator on my 60 with a GM one wire style alternator which has a lot larger charging capacity than the original OEM generator. So my new wiring harness will have to include a larger main lead to charge the batteries.
 

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Back to the hour meter question. The 40 never had an hourmeter from the factory, so I wouldn't want to guess if the one on your tractor is designed for 6 or 12 volts. You might find a marking on the back of it regarding voltage. I also agree with dieselshadow, 12 volt accessories typically can use smaller wiring than the 6 volts. The amount of amps used is what determines the size wiring you need. A 12 volt light bulb of equal wattage will require less amps(about half) than a 6 volt light bulb.
 

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Actually 12v systems use less current than a 6v due to twice the voltage. So the wiring for a 6v system is more than adequate size wise for the accessories on the tractor. The condition of the harness may dictate replacement as you said. It's fairly cheap and easy to do. One of the issues is the generator. I'm replacing the generator on my 60 with a GM one wire style alternator which has a lot larger charging capacity than the original OEM generator. So my new wiring harness will have to include a larger main lead to charge the batteries.
This is why I'm not an electrician!:laugh:

Rather than risk 60 year old wiring burning my tractor to the ground or having to troubleshoot the already patched together lighting circut in the dark, I have always just replaced it all. It's not like there is a whole lot of wires on a 2-cylinder.

I second the GM alternator conversion. If your local parts supplier doesn't know how to do anything besides look up parts on a computer, tell them you want an alternator for a '79 Chevy C10 with the 250ci straight six.
 
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