Posted by John T on August 07, 2012 at 11:20:02 from (216.249.82.117):
In Reply to: ceramic resistor posted by mb58 on August 07, 2012 at 10:41:43:
If an ignition ballast resistor (between IGN output of ign switch and coils input) were open (infinity ohms), then there wouldnt be any voltage on its output even if 12 was present on its input as should be.
The ballast resistor should measure continuty from end to end of around 1.25 to 2 or so ohms.
If theres battery voltage on the resistors input (from IGN output on Ign switch) and the output is connected to the LV Primary of a coil and the coils other terminal is wired to the distributor and the points were closed and good and working, Id expect 12 volts on the resistors input but only 6 on its output i.e. a 6 volt voltage drop ACROSS IT. ASSUMING A 12 VOLT TRACTOR WITH 6 VOLT COIL AND A BALLAST AND ALLS CORRECT AND WORKING AND POINTS CLOSED
If the points were open Id expect 12 volts on the resistors input and likewise 12 on its output.
TAKE AN OHM METER AND MEASURE THE RESISTORS RESISTANCE!! It cant be an open circuit but should be around 1.2 to under 2 ohms or so typical.
If for some reason (wiring wrong or a short etc) the output of the ballast was connected to the tractors frame ground, Id expect 12 on its input but zero on the output i.e. its dropping the entire 12 volts across it
If its a regular series ignition circuit ballast resistor (between ign switch and coil) and bad/open that can prevent a spark but shouldnt stop starter motor from cranking????????????
Sure its an ignition balalst and sure all is wired correct???
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