OEM ballast res. /ignition switch

(quoted from post at 10:50:20 06/02/16) what is the ohm rating of ballast res,and how will a bad switch act?

thank you
ary all over the map, roughly from a fraction of an Ohm (maybe 0.3) up to over 2.0
Depends on application, what vehicle, etc.
Many also are temperature dependent.
 
Hard to give you a real answer due to your lake of info. Some machines use a resister wire some use a thermister (sp) which as it runs the resistance goes up some and some use a resister wire which does not even look like a resister. As for a bad switch well that is sort of easy to test if it does not work at all but hard to test if it is a come and go problem. One simple way to test and ignition switch is a simple hot wire
 
2n with front dist.,12v neg ground starts and runs good at idle-full throtle no power and missing bypass ballast res. runs good at full power for about 5 mins and then starts to die.new points and cond. rotor cap plugs wires.
 
Well what does the spark look like when it starts to mess up?? Is it a good blue/white and jump a 1/4 inch gap or more?? Does choking it some hurt or help?? If you think it might be a bad switch simply run a hot wire form the battery to the switch and see if it stays running.
 
Since that started as a 6 volt, and has been converted to 12, and has a resistor, a good test to see if it is the right resistor would be to check the voltage from the coil side of the resistor to ground with the points closed. Should be around 6 volts.

While you have the volt meter connected, try turning the ignition switch off and on, wiggle the key, move the wires and terminals on the back. The voltage should remain steady any time the switch is on. If it drops, or the back of the switch gets warm, the switch is bad.

The bad running when warm could be the coil failing. Usually they will start breaking down with age, when warm. Might revisit the connections in the distributor, pull it off, check the point gap, all connections, ohm out the connections and points on the bench before putting it back on.

Also be sure the fuel tank is vented. Check the fuel flow through the carb. There is a drain plug in the bowl, with the fuel valve on, remove the plug, catch the gas in a clean glass. The flow should start strong, slow as the bowl empties, but still run a stream. If it slows to a drip, or stops, there is a restriction. Look at what comes out, check for water or trash.
 
art, you asked:

"what is the ohm rating of ballast res"

NOTE: I assume you meant an ignition ballast resistor in my answer:


CORRECT ANSWER IS IT DEPENDS on the tractor and coil resistance

HERES THE DEAL; Often if its an old farm tractor that uses a 6 volt coil on a 12 volt tractor and if you want to drop 6 volts across the ballast leaving the correct 6 volts for a 6 volt coil, THE BALLAST RESISTANCE IS "CLOSE" TO THE COIL RESISTANCE so it acts like a 50/50 voltage divider, 6 across ballast 6 across coil, got it????

Therefore, some (NOT all) typical ballast intended to use a 6 volt coil on a 12 volt tractor are around 1.25 to around 2 ohms AS THATS THE SAME RESISTANCE AS MANY 6 VOLT COILS so the ballast reduces 12 volts down to 6 for a 6 volt coil

NOW BEFORE ANYONE HAS A CALF different tractors may use different then the above ballast resistance THATS WHY I SAID THE CORRECT ANSWER IS IT DEPENDS !!!!!!!!!!!!!!!!!!!!!!!!!! Some tractors and ignitions may be far less ohms !!!!!!!!!!!!!!!! Also the duty cycle and dwell time affects ballast choice due to the points opening and closing IE it may NOT be a perfect 50/50 voltage divider as my static example above illustrates. Ive seen some where the coil voltage may be more like 7 then 6 volts!!

BAD SWITCH: It may have carbonded or loose resistive contacts which drops voltage so the coil gets low voltage and the spark is weak !!!!!!!!!!! With the ignition ON and points closed measure the voltage drop across the switch contacts,,,,,,it should be near zero volts but if its 1/2 or more volts the switch is resistive and bad. Likewise measure voltage to the coil with ign on and points closed, if switch is good there shouldn't be any voltage drop (not counting ballast here) ahead of the coil.

Try a hot jump wire direct to the coil to by pass switch and see what happens!!!!!!!!!!!

John T
 

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