coil

[jpmcleod 4]

I have a Bronco 14 and I can't get fire from the coil. It was running fine and now nothing. It has the toggle switch for ignition power on/off and a push button on the dash to activate the starter.

I am not good at explaining this but it has the trigger behind the flywheel and a single wire (electronic ?) coil.

Question. Should there be constant power to the coil or only when the trigger comes in contact with the flywheel magnet. It has been wired with constant power and ran that way for over 2 years but I question the constant power to the coil.

If someone has a wiring diagram or any knowledge of the wiring it sure would be nice.

I found a new coil but it is $152.00 and I cannot spend that much without knowing if the coil is the problem. I would hate to burn up a new coil at that price.

Thanks.

[Save Old Iron 1,568]

Jp,

yes, a hard system to isolate out the exact culprit and the $$ stakes for parts are high.

the single wire leading from the stator winding will not have a constant voltage on it - the magnet on the flywheel will generate a pulse from the coil of about 100 volts which is sent to the trigger unit "A" terminal. Its a quick pulse - you could see it with a scope but not with a multimeter.

The 100 volt AC pulse gets stored in the trigger box and when "triggered" by the pins on the flywheel, dumps the 100 volt charge to the primary of the ignition coil and zap - secondary spark.

You CAN measure the secondary coil resistance - about 10,000 ohms

you CANNOT measure the primary resistance since there is a capacitor embedded in the coil - no DC current flows - so no static resistance check is possible. I believe there is a resistance check of the primary in the service manual but the check is for infinite resistance. The assumption there is the capacitor is not shorted. Fine, but infinite resistance could also be seen with a good capacitor and an open primary winding - so not the most effective test.

This is a guess, and a long shot, but you might be able to take a neon bulb electrical tester and bridge it between ground and the wire connecting to the "A" terminal on the trigger unit. Neon bulbs ionize (lite up) at about 90 volts - so maybe - just maybe the bulb would flash if the stator charge coil is good. If you have an oscilloscope, measurement is easy.

Again, this is a difficult system to troubleshoot without spare parts or the right tools.

Just out of curiosity, anybody know what the 1970's $$ cost was for a trigger unit or secondary coil assy. They could not have always been in the $150+ range ?

[Save Old Iron 1,568]

something I forgot

try disconnecting the wires to the KILL switch. If the internals of the switch are shorted or dirty, even in the run position, the short to ground could be killing the pulse to the primary of the ignition coil

[rmaynard 16,198]

If someone has a wiring diagram or any knowledge of the wiring it sure would be nice.

This is not a real good copy, but it's the best I have. If you want a copy of the entire manual, PM me with your email address and I will send it to you.

[jpmcleod 4]

I knew I could count on you. I will pull the sheet metal off today and make sure the trigger is tightly bolted and all wires are correct.

Only one important question. Does the coil have constant power going to it when the ignition is in the "on" position and not damage the coil?

Good to hear from you. It has been a while but if you look back. this is the same tractor you helped me with before.

[tommy3horse 3]

Hello,

I am just throwing my 2 cents worth here.

I just encountered the same issue with a Raider 12. The PO had removed everything and I got it all apart and was not going to spend big bucks restoring the electronic ignition components and opted for points and a coil instead. I needed a new key switch and of course the coil and point set. I think I spent around $60 and now I have a reliable unit.

So, my point is that if you are not particularly fond of "originality", chuck the electronic stuff in favor of a dependable, reliable points and coil set-up.

Tom

:woohoo:

[TT-(Moderator) 1,161]

Only one important question. Does the coil have constant power going to it when the ignition is in the "on" position and not damage the coil?

If you're asking if this type of ignition system needs power from the battery to function.....

NEVER apply power to the "kill" wire. It must be grounded to stop the engine.

[Save Old Iron 1,568]

Speak to us JP

What you up to?

I don't like it when its too quiet.