h farmall 12 volt conversion

I put a 12 volt conversion alternator on my super h farmall. I put 12 volt battery juice to the new resistor and checked through voltage with a meter. The voltage through the resistor, coil and distributor remains 12 volts. Is this normal? If I start the engine with the alternator voltage will it destroy the points?

Did you get a conversion kit? Where, I'm wanting to do same.

John

When you first energize a ballist resistor it will not reduce voltage. It has to warm up to do that. So if you are just pulling out the ignition switch and checking it right away it's going to read battery voltage or very near battery voltage. After a few minutes it should be hot to the touch and then it should reduce voltage to the desired level.

12 volt conversians are not hard at all. It is nice to have talor made brackets but really not needed for the H or M.



Thats my M with a Delco alternator. Flip the genny bracket over and it's easy.

Rick

If the points are open, 12 volts thru the resistor, coil and dist is normal.

Try turning the crankshaft just enough to close the points then take your voltage readings again. You should get battery voltage on the switch side of the resistor, approx 5 - 7 volts on the other side of the resistor and at the coil "+" terminal, and ~0 volts on the coil "-" and distributor terminals.

yes.

Bob M is right on track.

Is it normal????? NOT USUALLY

Usually the points are closed, they only open when a piston is near TDC to fire a plug, and engines dont usually stop with a piston in that position.

As my friend Bob M noted if the points are closed (which they usually are when a tractors setting there not running) theres current flow from the switch to and through the resistor,,,,,,to and through the coils LV primary,,,,,,,,to and through closed points to ground so theres an I x R Voltage Drop (around 6 volts) across the resistor leaving 6 on a 6 volt coil. If theres no current flow (points open) theres no I x R voltage drop as 0 x 1.5 ohms = 0 volts

John T

Rick, FYI the "resistor" type of device you describe is known in the trade as a "THERMISTOR". Its a type of resistor that increases its resistacne over time as it heats up.

I have seen thermistors used in ignition circuits to replace the start up ballast by pass system where a switch contact actually by passes the ballast to apply unballasted battery voltage on the coil ONLY while cranking. (i.e. it does it without any ballast by pass switching system)

HOWEVER the typical generic ignition ballast resistor (the white ceramic bathtub enclosed wirewound units) IS NOT A THERMISTOR and its typical resistance (maybe 1.2 to under 2 ohms) is there immediately at start up and afterwards also (sure it may increase slighly with heat).

Im not sure if the poster has a normal typical ballast resistor or a thermistor, maybe some of the after market kits supply a thermistor instead of a normal bathtub style resistor??? If its indeed a "thermistor" it will function as you indicate, but if its a normal ballast resistor it will still have its resistance (around 1.2 to under 2) right from the get go

Darn if I know what he has lol

Fun chat, hope this helps

John T