How to tell if coil needs ballast/=?

coils/points should be limited to about 4 amps, so take 12V / 4 amps = 3 ohm, 6V / 4 amps = 1.5 ohm.
 
A coil that reads around 1.5 ohms need a ballast resister if used with 12 volts. If the coil reads around 3 ohm it means it is a true 12 volt coil
 
What terminals or just where is this measurement taken? Also hopefully your mother is recovering from her fall Thanks for the answers
 
Across the small terminal and be sure no wires are hook up when to do that or you can get a false reading
.

As for my mom see fell again this morning. She will probably be seeing a doctor in the next day or so to see if maybe she had a stroke
 
Hi I ex neighbor, good question "How to tell if coil needs a ballast?' here's the answer

If its a 6 volt tractor the coils LV primary resistance as measured between the two small terminals should be somewhere around 1+ to 2 ohms, many around 1.5 ohms, and IF SO NO BALLAST IS REQUIRED thats a coil for a 6 volt tractor AND YOU DONT NEED ANY EXTRA BALLAST on a 6 volt tractor.


If its on a 12 volt tractor, the TOTAL primary resistance (thats coil + any ballast) needs to be around 2.5 to 4 ohms THEREFORE

a) If the coil has ONLY 1 to 2 ohms resistance (like a 6 volt coil does) THEN IT NEEDS A BALLAST otherwise it will overheat

b) If the coil has 2.5 to 4 ohms resistance THEN NO BALLAST IS REQUIRED

Typical 6 volt coils are around 1+ to 2 ohms (many 1.5) while typical 12 volt coils are more like 2.5 to 4 ohms (many 3). If you use a 6 volt coil on a 12 volt tractor THEN YOU NEED TO ADD BALLAST or else it will overheat.

To measure resistance place an ohm meter on the low ohms scale across the two small coil terminals thats NOT the big high voltage terminal tower

Take care my friend

John T
 
If she has been on blood thinners, warfarin,
for an extended period of time,
have them check for bleeding on the brain.
 
when measuring across tw0 small terminals meter pegs. When measuring from one small terminal to tower i get 4 ohms . do not understand why small terminal to terminal meter pegs to far right of scale ???
 
I bought distribute used from a international M . I feel sure the m was converted to 12 volt. Ther was no ballast that I could see. Going to try it out as is. Thanks to all.
 

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