Re: Re: Which is best when changing to 12v?

Posted by jdemaris on November 21, 2003 at 05:48:53 from (209.23.28.63):

In Reply to: Re: Which is best when changing to 12v? posted by 49 Cubber! on November 20, 2003 at 17:38:13:

If your mention of a "resistor to the starter" is in response to my posting, you seem to have mis-read it. I mentioned a resistor "bypass", which actually has nothing to do with the starter. A tractor with a 12 volt battery and a 12 volt starter will generally drop to a system voltage of somewhere around 9 volts when cranking. That's why, when being tested, a 12 volt battery is load tested at 9 volts. So . . . when a tractor is being cranked, the coil will also be getting around 9 volts if its getting full system voltage. If it's hooked to a resistor, it might be getting only 4-8 volts - which is still enough to start and run in most conditions, but sometimes won't in cold weather, with fouled plugs, bad wires, wet cap, etc. That's the reason why most ignition systems have some sort of way of bypassing the resistor when the engine is cranking. Ford had the bypass built into their relays, Delco had it built into their 12 volt solenoids. Some companies built it into their starter switches. It's a simple thing to do, and can be added to any tractor with $10 in parts. There are also some coils built with internal resistors that are heat sensitive, and kind of accomplish a sort of "bypass." When cold, they pass full current, but once running for awhile, they heat up, and resistance increases, voltage drops, and thus the life of the ignition point life is enhanced.
Another way to increase voltage during cranking is to use a bigger battery. The bigger the battery, the less voltage drop during cranking.
I don't want to make an academic study out of this and get over-technical. My point is, if someone wants to take to time to update their tractor, why not take an extra ten minutes and do it right?

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• Re: Re: Re: Which is best when changing to 12v? 49 Cubber! 08:44:48 11/21/03 (0)

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