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Harry Ferguson Tractors Discussion Forum
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Ballast Resistor, TO 20

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D West

06-21-2004 05:06:10




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Hi Group,
I'm having serious ignition problems... she starts easily, but runs very poorly, misses, stumbles, no power under load. Removed, cleaned and checked/changed all wiring connections. It's an old 12 volt conversion, just installed a new 12 volt coil and ballast resistor. After idling for several minutes, the coil is very warm to the touch, and the ballast resistor ceramic is way too hot to touch. Is this normal?
Thanks for any help...
Dennis

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Jerry/MT

06-21-2004 21:27:48




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 Re: Ballast Resistor, TO 20 in reply to D West, 06-21-2004 05:06:10  
Dave,
If you bought a 12 volt coil, you should not need a ballast resistor. The resistance is built into the coil. With 12 volt systems, you need the ballast resistor only if you use the old 6 volt coil. It limits the current in the 6 volt coil to keep it from overheating. Another thing you may want to check is the wear on the ditributor shaft and bushing. My old distributor was so bad that with the points closed, the radial runout of the shaft/bushing combination caused the points to open to 0.030" when I pushed radially on the shaft. You might want to check and see how bad your distributor is. An outfit in Portland , OR (www.philbingroup.com)rebuilt mine for $100. I added an Pertronix electronic ignition and it starts and runns like a dream.
Hope this helps.

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D West

06-22-2004 07:34:55




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 Re: Re: Ballast Resistor, TO 20 in reply to Jerry/MT, 06-21-2004 21:27:48  
Jerry/MT and the other guys,
The coil I replaced was an old 6 volt coil which had not been changed when they converted it to a 12 volt system, with the resistor behind the dash. The new 12 volt coil said it was to be used with a resistor, so I replaced it also. When we first began trouble shooting, I discovered the same exact problem with my distributor; the radial slop on the shaft was so great that half the time the points would not even open. I had it re-bushed at a local generator shop here in Ft. Worth, and my Dad reinstalled it and timed the engine in about 30 minutes... (he's a retired aircraft mechanic). It fired up silky smooth and purred like a kitten, it had never ran so well; very quiet with plenty of power, it was like a new tractor to me. A few days later while brush hogging for about an hour, it suddenly started failing with the aforementioned symptoms. As to how it's wired, I'm at work right now and will try to state by memory, not sure if I'll get it right: it's the single wire from the alternator to the amp gauge; to the ignition switch; to the ballast resistor; to the positive coil terminal.
Thanks,
Dennis

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Jim W

06-22-2004 10:50:50




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 Re: Re: Re: Ballast Resistor, TO 20 in reply to D West, 06-22-2004 07:34:55  
Oddly there are coils marked 12v that are meant for use with ballast resistors, and coils marked 12v that are meant for use without them.
With the points open and the key on, you should see battery voltage at both sides of the resistor, as well as both sides of the coil. (With points open, no current flows [after the condenser charges which is very fast] and hence there should be no voltage drop.)
With points closed, you have a voltage drop across the coil, and across the resistor, the sum of which is supposed to be battery voltage. They ought to be roughly half and half but maybe not too exactly, not sure.
So with points open, if you have less than battery voltage on the points side of the coil, that would indicate a leaky condenser.
Hope that helps; can't find a clearer way to write it.
Jim

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Barry from Stirling

06-21-2004 05:40:26




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 Re: Ballast Resistor, TO 20 in reply to D West, 06-21-2004 05:06:10  
Morning. I had on old balist resistor and coil on my 52 TEA-20. They were both in pretty poor shape. When I overhauled my tractor. I bought a new 12 volt coil. On the package it said " 12 Volt coil WITHOUT series resistsnce " I made a few calls and quickly found out that I could throw away the old balist resistor.Made wiring the tractor a breeze. My new coil is very warm to the touch but works perfect. Just my thoughts

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mr chapp

06-21-2004 05:29:01




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 Re: Ballast Resistor, TO 20 in reply to D West, 06-21-2004 05:06:10  
From my experience this is normal. The other option to a resistor is an internal resistor coil. Do you still have a problem after adding the coil & resistor? If so the condenser may be at fault. Good luck, have fun!!



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D West

06-21-2004 06:44:56




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 Re: Re: Ballast Resistor, TO 20 in reply to mr chapp, 06-21-2004 05:29:01  
When I purchased the coil it said to "Use with ballast resistor # xxx ", so I purchased it also. It looked exactly the same as the old one that was mounted behind the dash, and I replaced it. I didn't realize that they got so hot. I've checked the voltage going into the coil... 10.5 volts, and 5.5 volts coming out of the coil. I guess it could be a faulty coil. We temporarily bypassed the condensor, with no results. This has really got us stumped, but we know it has to be something simple...

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Jim W

06-21-2004 07:56:36




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 Re: Re: Re: Ballast Resistor, TO 20 in reply to D West, 06-21-2004 06:44:56  
I think you should have less than 10.5 volts at the coil, more like 7 volts, but I could be wrong. At the points side of the coil you should have either the same voltage (7 or so) or else 0 volts, if the points are open or closed repectively. It sounds to me like something isn't wired right.
Can you explain how it's wired?
Jim



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