SC Starts Sometimes-Ballast Resister

Bud W · Jul 1, 2014

OK My SC with 12 volt Battery and Ballast Resister doesn't want to start but will run OK when it does decide to go. When I measure the voltage to the coil I'm only getting 4 volts. My question is can a Resister fail such that you get 4 instead of 6 volts of output? And secondly would this make it hard starting and yet occasionally start and run?
Thanks

gene bender · Jul 1, 2014

4v isnt enough to make a good spark change that balast resistor.

Bob · Jul 1, 2014

LIKELY (I didn't look it up)your tractor has a "starting bypass" setup that takes full battery voltage from the "R" terminal on the starter solenoid and bypasses the (run) resistor during starting.

So, if all is as it's designed to be, the ballast resistor isn't even in the circuit during cranking.

Bud W · Jul 1, 2014

The Resister is in the line to the coil. Its supposed to reduce the voltage to 6 volts to the coil. There isn't ant type of bypass. Thanks

El Toro · Jul 1, 2014

Check your specific gravity in each cell using a hydrometer. Should be in the 1.275 range or better. You may have a weak cell in your battery.
Also check the charging voltage across the battery terminals using a volt meter with the engine at 1/2 throttle or better. Hal

rvirgil_KS · Jul 1, 2014

Is this a new conversion from a kit? resistor and coil primary (+ to -) should both be about 1.5 ohms. I've seen some resistors in kits that were higher and did as yours. I had one in an 8N ford that measured over 5 ohms. Check the resistance of your resistor and coil.

Bob M · Jul 1, 2014

Try temporarily bypassing the ballast resistor. If the engine now starts/runs, the ballast resistance is too high. (It won't harm the coil/points to run it a few minutes with the resistor bypassed)

Assuming you have a stock 6 volt coil, a 60's era Chrysler resistor (Autozone #AL795 or equivalent) is what you need.

Bud W · Jul 1, 2014

No this circuit has been in operation for many years and it always started on the first hit of the starter. I think I have a voltage drop through the ammeter/fuse circuit. I have 12 volts input to the ammeter and much less out of the fuse holder and sometimes no voltage at all. I'm going to bypass the fuse and see where things stand.

willie in mn · Jul 2, 2014

Bingo, we have a winner. You just answered your own question, voltage drop way upstream from the coil. Sometimes just twisting a fuse in the holder scrapes off a bit of corrosion & makes a better connection.
A resister is like the filament in a light bulb, it either works or it doesn't.
HTH
Willie

John T · Jul 2, 2014

" I have 12 volts input to the ammeter and much less out of the fuse holder and sometimes no voltage at all"

Id guess THATS YOUR PROBLEM (much less or no voltage at all just isn't gonna work) instead of the ballast resistor, and Id suspect the fuse holder as the problem (rust, corrosion, loose weak contact) more then the ammeter.

John T

Bud W · Jul 2, 2014

Well I'm not sure exactly what the problem was but after removing and reinstalling the fuse holder everything seems great-6 volts at the coil and the old tractor roars to life with just a brief hit of the starter. Thanks to all that responded.

SC Starts Sometimes-Ballast Resister

Bud W

Member

gene bender

Well-known Member

Bob

Well-known Member

Bud W

Member

El Toro

Well-known Member

rvirgil_KS

Well-known Member

Bob M

Well-known Member

Bud W

Member

willie in mn

Well-known Member

John T

Well-known Member

Bud W

Member

Similar threads