MTFCA Forum

I’m helping a buddy with the ‘22 he bought. He’s been able to drive it about 200 miles, dealing with problems as they appear. It used to run good on mag, now the mag appears inoperative. It has an oil line attached at the mag post. Anybody have any experience with what the problem might be or suggestions as to how to proceed?

I would check for voltage at the mag post terminal with the engine running about 800 rpm. Use an analog AC voltmeter. If you dont see voltage from the mag post to ground, the problem is likely the internal contact at the mag post. If voltage is present with the engine running, there is probably a problem with the wiring or the ignition switch.

Thanks. I checked the wiring and switch. Also tried a jumper from the mag post to the coil box with the switch off, bypassing everything. No go.
I don’t have an analog meter so with the engine running on battery I carefully touched the mag jumper to ground...no spark.
Are the three screws that hold the mag post threaded into the hogshead? We’re afraid to loosen them for fear of dropping a nut or something into the tranny.

Sometimes band lint gets caught between the mag post and mag ring contacts.

Not a problem removing the mag post. The hogshead is threaded for the screws and there is no way you could drop anything into the post hole once you remove the post.

Tim

Loosen the three machine screws and lift up that mag post. You may have to loosen and/or remove the oil line to the fitting.

These have an internal spring, like a ball point pen spring, inside that pushes out the needle for contact to the coil ring solder blob. Check to be sure that contact is working.

Most times its crud causing ground and lost of AC power.




Here is one with Kevlar fuzz, excessive since the drums were filled with pits and sharp edges, that shredded the linings.

Three things I can think of which could quickly make the mag stop working. These two are most likely.
1. Contact with mag terminal to magneto inside could be open. Sometimes band lint or other debris gets inside and breaks the contact. Cleaning it out will usually correct that problem.
2. Some of the posts with the oiler are just a bit short and do not make good connection. Sometimes this can be fixed by extending the tip with a few drops of solder. Other times the use of small fiber washers on the inside can push the tip farther in. It looks like you have plenty of threads on the end where the wire connects, so if you remove the two nuts you can work the contact out the inner end and install one or more fiber washers on on the inside which will push the contact closer to the button at the top of the magneto.
3. Unfortunately, this one cannot be fixed without pulling the engine and separating the flywheel from the crankshaft. This would be something has come loose inside and cut the windings on the magneto coil ring causing an open circuit.
Other things which can cause the problem would be magnets too far from coils. This would come on slowly, and it might run at higher speeds, but not idle on magneto.
Or the magnets could be de-magnetized. This can happen rapidly, if the battery or generator should accidently be connected to the magneto circuit.
Norm

We removed the post and got a bit of a surprise. No fuzz.
First, the brass spring-loaded post was off center and when removed appeared to have been repaired. It also has a little bend to it. It was insulated from the collar by what appeared to be a piece of plastic hose and two nylon washers...the inner one of which was half missing.
Looking into the hole with my cheapie borescope we saw two dimples in the contact surface. We think the post should be replaced regardless....should we worry about the contact surface?[attachment

It’s not an issue removing the mag post. Loosen the 3 screws and move the post to one side and check for lint or debris. One thing that hasent been mentioned is to make sure the contact post is making a good contact to the coil button on the mag ring. This sometimes can fool you!
Occasionally when you reinstall the mag post the mag contact will be off to one side when tightening down the mag post! And sometimes the mag post contact button is not exactly in line with the hole on the transmission cover. If it’s that way the mag post contact will bend over a bit to make the contact. And eventually lose a good connection.

The dimples in the contact button surface should cause no trouble. Just make sure it's reasonabley clean.

The dimpled contact surface usually means you have a older original mag ring that’s still working. The rebuilt ones I’ve used will usually have a newly soldered button. I think you’ve found your issue. Buy a new mag post with oiler connection and install it. One thing to remember with a new mag post with the oiler connection is to make sure the new fitting will install with your old oil line or replace the entire oil line oiler assembly on your car.
The repos don’t always interchange well with each other. Especially if the repo you might have is one of the older ones. Just a heads up!
The little bend on the contact spring may indicate the lead button is off center with the cover hole. That’s exactly what’s wrong on my 1919 Roadster. It works Ok but I have to make sure about the angle when I remove and reinstall it. Don’t ask me how I know! Good luck with your car.

Someone mentioned metallic debris getting caught in lint at the mag post. I wonder if that doesn't explian some weak mag situations. I'd think metal debris in lint at the post and button would have a good chance of forming a resistive, or partial short that would ground some of the mag output, but not necessarily all of it. The result would be a weak output, not a dead mag.

My friend Gene and I want to thank all of you for the information. Model T's are certainly a learning experience. Gene is going to order a new mag post tomorrow so fingers crossed that it solves the problem. The one he removed had poor insulation - just a piece of plastic tube between the brass post and the aluminum collar and a couple of nylon washers. The post sold by Langs looks to be much better constructed.

Oldav8tor wrote: ↑

Sun Sep 19, 2021 6:39 pm

My friend Gene and I want to thank all of you for the information. Model T's are certainly a learning experience. Gene is going to order a new mag post tomorrow so fingers crossed that it solves the problem. The one he removed had poor insulation - just a piece of plastic tube between the brass post and the aluminum collar and a couple of nylon washers. The post sold by Langs looks to be much better constructed.

That is a particularly junky pick up. You got nothing to loose fixing/adding better insulators. Done on this unit before. Then try for out put readings.

Update. My friend Gene ordered a new mag post from Langs. With it installed, the magneto works fine. We're not entirely sure what caused the failure of the original but we have some ideas...at this point we're just glad it's working. Thanks again for the info and advice.