Farmall H electrical system

I recently purchased a 42 H, the seller was not the original owner and he said that he thought that the tractor had been switch over to 12 volt. I replaced the battery and was informed that it was using an 8volt battery. Even with the new battery the tractor still lags when turning it over. Tonight i had to really work with it just to get it to turn. How do I tell if the tractor has been switched to 12 volt. I'm assuming using an 8 volt battery on a 12 volt system would be causing the tractor to lag on start up like its doing. Thanks in advance.

There are 12v generators, but alternators are far more common on conversions. The presence fo an alternator would be a dead giveaway of a 12v conversion.

If you have a battery ignition (as opposed to a magneto) ou might look over your coil to see if it indicates that it's a 12v, but that wouldn't be as sure as the alternator. Some cois are built to step down internally, from 12v to the 6v to the points. Others require an externalresitor to step the voltage down beforeit gets to the coil. If you trace back the wire leading into your coild from the battery end and find a resitor in it somewhere, that would be another sign that it is 12v.

As far as the hard turning, I'd hazard that you have a poor connection somewhere. Shiny and bright is the rule for all terminals, lugs and connections. Make sure you'e got good connections at the battery terminals. It's a good idea to cleanup around where the ground cable bolts to the chassis -- clean the underside of the bolthead to mare metal, as well as a small area under the lug on the cable. Metal to metal is what you want -- paint is a poor conductor.

Apart from that, you could have poor or inadequate cables. If you detect objectionable heat anywhere along the cables after cranking, that would be the place to look for corrosion of your cable ( most common near the battery terminals)or a poor connection

It's not a 12 volt system unless it has a 12 volt battery. Most conversions use the original 6 volt starter anyway. 12 volts will not hurt it. But,an H doesn't need 12 volts, or even 8. Use at least 2 gauge cables and keep the connections clean. It will be fine.

First the cables and connections, then the starter motor should be tested. If the bushings are worn, it will drag internally. It should draw about 350 amps to 450 amps. If more, Like 600, it is in need of rebuilding. A meter is available that is held against the cables to check current draw (cheap and effective) JimN

If you require a ballast resistor, be sure it is the correct one. I found it out the "long" way that I was given the wrong one. I use a 13 ICR from NAPA on my 12 volt conversion on my 44 H.