Purpose of Resistor bypass?

[FC Andy]

Hi guys,

I drug out the old 450D and am going to get it going again. I've gotta put new bands in the PTO and rewire the tractor at minimum to get it useable again. So, my question is- Does anybody notice better starting if they have a bypass for the ignition resistor? The book shows it was originally wired that way, I plan on returning it to a 6 volt coil, with resistor, and setting up the resistor bypass. I know it's to increase voltage to help them start easier, mine was wired with a 12V coil and started ok, would it start better with a bypass around the resistor? Got a picture for y'all, too. -Andy

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[jeffcat]

Not to rock the boat but I thought all 450's were 12 volt?

 

[FC Andy]

I don't know if ALL 450's are 12 volt or not. The Diesels are, anyway. My owner's manual's wiring diagram shows a resistor on the ignition. So, IH used a 6v coil and resistor from the factory on this particular tractor. The parts books also list 6v coils as original equipment. When I got the tractor, someone re-wired the tractor, and put an alternator on it. I had to push a button to excite the alternator, and it wouldn't stay charging all the time. So, I cut all the wires off of it and am starting from scratch. When I got it, the re-wire job included a 12v coil without a resistor. The tractor started ok in the summer, but was a bear in the cold. I want to know if returning the tractor to the way IH did the ignition, IE a 6V coil with a resistor and a resistor bypass circuit, will make the tractor start any noticeable amount better. I'll also set up my 10SI alternator the correct 3 wire way. -Andy

 

[old]

12 volt tractor but a 6 volt coil. By bypassing the resister it give a lot hotter spark for start up and then normal run the resister keeps the voltage down at the 6 volts the coil need to keep from burning points and blowing up the coil and yes a 6 volt coil can blow up BTDT and boy what a mess a blown up coil makes

 

[Arnold Layne]

Just a couple days ago you told me that coils almost never go bad???

 

[old]

Yes they almost never go bad if and that is the big thing you have the correct voltage to them. a if you have a 6 volt coil hooked to 12 volts and no ballast resister the voltage it not correct and yes then the coil can and will one has to be smart enough to figure things out

 

[Andy Martin]

It should help. Old Chevrolets had the same setup with a bypass wire from the starter solenoid directly to the coil.

 

[Arnold Layne]

So the coil that blew up was on your 841 Ford?

 

[John T]

YES in BOTH theory and in reality, a 12 volt tractor that uses a 6 volt coil plus a ballast by pass system when cranking can start better especially at colder temperatures. If all is good and its not extremely cold you may never see any difference.

John T

 

[D Slater]

F-450D started out with a 6 volt coil with no resister used. With the short run time on gas they figured they would be okay. At F-450D serial # 13491 a 6 volt coil with resistor started. It was the same 6 volt coil that gas models used but it had diesel marked on it from IH and a different part number. This coil was used as a replacement for all. Most of the 400D used a 12 volt coil until near the last ones they used the same 6 volt without resister that 450 did below 13491.

 

[pete 23]

The latest and greatest system on a 450 diesel was a 6 volt coil, NO REISTOR and no bypass system. For the few minutes it runs on gasoline cycle it was deemed that the resistor and bypass was not necessary. I don't know if any came out in production wired that way but that is what service bulletins said to do with them. Most are still wired with 6 volt coil and resistor and bypass for starting though. One thing for sure, you don't want a straight 12 volt coil as you need the hottest spark you can get.

 

[old]

NO it was on a 1957 VW bug that I had and I left the ignition switch on. Probably way before you where in diapers 6 volt system that I did not was a 6 volt system so had a 12 volt battery in. But here one for you why attack me why not try to help others????????? I do my best to help not attack but you sure seem to like to attack. By the way do you have clue what ohms law says or what E equals M C squared means. I was a NAVY E.T. so those things I have long since forgotten

 

[Arnold Layne]

I was just curious, you said you had only seen one coil go bad and that was on your 841. And yeah, I know what that stuff means, but I have not forgotten it.

 

[FC Andy]

Well, maybe I'll wire it up without a resistor, and If I have coil issues I can add a resistor and bypass circuit later. -Andy