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coil question

A

Anonymous-0

Well-known Member
I have a farmall 100 which has been converted to a 12 volt. How do you check a coil to see if it is working ok? thanks
 
First thing to check is your points because of the points are bad the coil CANNOT work. Coils are almost bullet proof and do not go bad very often
 
Coils will however go bad it you convert a 6 volt system to 12 volt and don't add an external resistor to the ignition circuit on the coil supply side.
 
I must disagree; the POINTS will go bad quickly if no resistor is used on a 12 volt conversion. A resistor is not needed if the coil is designed for 12 volts (internally resisted).
 
I have run many 6 volt coils on 12 volts and they have lasted for years, but the points do not last as long. But coils are not prone to going bad but points are
 
turn switch on, and check to see if fire is going to switch side of coil, if it is turn switch off and go to next step.

remove coil wire, replace with a plug wire with a spark plug inserted into the end, ground the spark plug. remove the wire going from coil to distributor, from distributor, turn ignition switch on, strike wire to ground, spark plug should fire if coil is good.

spark plugs fire when points close.
 
They fire then the points open. In your test, the coil will fire when you unground the coil-to-distributor wire.
 
You have it backwards. The coil fires when the points open not when the points close. If you think about it there is 4 lobes on the distributor shaft and when ever the points open the rotor lines up or should line up to a plug wire on the cap
 
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