Mag just quit while driving

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Model T Ford Forum: Forum 2016: Mag just quit while driving
Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Laughary on Friday, August 05, 2016 - 09:37 pm:

Until today the car ran best on mag except at low idle. My question is whether a mag would quit putting out suddenly like this for any reason other than a connection coming loose.

The mag was not working when I got the car in June, but began working when I cleaned up the connector. I also need to replace my ignition switch because the low beam headlights sometimes don't come on without wiggling it and the tail light stopped working today on low beam.

I'm ordering a new ignition switch and hope that solves everything.

A mag would fail slowly, right?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Michael Garrison - Rice Minnesota on Friday, August 05, 2016 - 09:48 pm:

No, a magneto can fail at the drop of a hat, or cap or... Chances are you have lint from the transmission bands on the tip of the magneto post. Or you might have excessive end play on the crankshaft, or your ignition switch could screwed up or there's an internal break in the wire between the magneto post and the switch or when you pulled your starter out you tried to get it out before pulling the be did and you destroyed your coil ring or... I'd start by pulling the magneto post.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Michael Garrison - Rice Minnesota on Friday, August 05, 2016 - 09:49 pm:

Not "be did" bendix! Damn auto-incorrect got me.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Laughary on Friday, August 05, 2016 - 09:52 pm:

Thank you

I will track down the wiring possibilities first.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Michael Garrison - Rice Minnesota on Friday, August 05, 2016 - 09:55 pm:

Chris, a word of caution, most digital volt meters won't register on a magneto as will the old analog volt meters will.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Laughary on Friday, August 05, 2016 - 10:17 pm:

Thanks

My old analog ammeter shows output but I never figured out the numbers, so I'm not sure how many volts.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Jelf, Parkerfield KS on Friday, August 05, 2016 - 11:04 pm:

If the meter shows output at the post, there's probably enough juice to fire the coils. It doesn't take much. Check the switch and all connections.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Laughary on Friday, August 05, 2016 - 11:13 pm:

Thank You but I misspoke and am still trying to get a good connection with the ammeter. It took awhile before and I remember accidentally causing a spark before getting results before.


Top of pagePrevious messageNext messageBottom of page Link to this message  By samuel pine on Saturday, August 06, 2016 - 02:31 am:

And then I was humming along 5yrs ago and it
back fire, I switch to Batt. Test lighted the
mag. terminal got a fat -0-. no lint contacts
perfectly clean. Been driving on Batt ever since.
Back this June my youngest boy goes to Napa for
supply's, he arrives at shop I notice the key
on Mag? I say how long you been driving on Mag,
of course the kid says I don't know? I try it
and It runs perfectly (like it use to) on mag.
Guess it needed a 5 year sleep. so go figure.
sam


Top of pagePrevious messageNext messageBottom of page Link to this message  By bob middleton on Saturday, August 06, 2016 - 10:26 am:

Pull the mag post make sure it lint free


Top of pagePrevious messageNext messageBottom of page Link to this message  By Michael Garrison - Rice Minnesota on Saturday, August 06, 2016 - 10:41 am:

Chris, describe what happened when you accidentally caused that spark. I'm not sure how to describe what exactly happens but I think you have to be careful when playing with wiring. There's a chance you can cause the magneto magnets to become de-magnetized by crossing the battery with the magneto. (I apologize for such a lousy explanation.) I guess the magnets can be recharged if such a thing happens.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Laughary on Saturday, August 06, 2016 - 10:44 am:

Thank You all.

Sam, mine ended with a backfire, too. Ha. Nothing new happens to these old cars, just new owners.

Mag sensor fell apart as I removed it, so I Replaced it late last night, but still no output yet. I'm busy until Monday but will think through it some more until then.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Laughary on Saturday, August 06, 2016 - 10:47 am:

Hi Michael,

Mag had no output when I bought the car in June. I tried a test light and recall it taking awhile before it got a good connection and it sparked on the hogshead where I had it grounded.

Then, voila! It ran better on mag than ever on battery.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Saturday, August 06, 2016 - 10:58 am:

It happened to me about 20 years ago right after installing a rebuilt engine. Drove it a few miles and the mag quit. I switched to battery and drove for about 10 years. I was restoring a second T and rewound 3 magneto rings using instructions in the book "Electrical System" I used one in the T I was restoring and decided to fix the magneto in the T I had been driving for about 10 years. I pulled the engine and this is what I found. The funnel from the inside oil line was laying in the bottom of the crankcase and the magneto coil was cut and open. I had been driving for 10 years with only the oiler without the funnel and the mag post oiler.

I only needed to take out a few shims and replaced both the magneto coil and the oiler. Now my car has changed from one of the slowest on tours to one of the fastest!

Anyway, any foreign object which makes its way to the crankcase, especially something which will stick to the magnets, can cause the magneto to quit. It is also a good reason for an auxiliary oiler system.

Hopefully for you it will be easier to find and repair such as a bad ignition switch, loose wire or dirt on the magneto plug.

Other things can cause the magneto to quit: magnets need charge. End play in crankshaft causing too much gap between magnets and coils. These two causes will usually cause the engine to stop running on mag at idle or slow speed, but will still work when going fast. Gradually the mag will stop working at any speed.

Test for power output at magneto connection top of hogs head. Use a light bulb with an analog AC volt meter to check. There are other posts explaining how to make that test. This test will tell you whether or not the magneto is working and how much output you have from it. Do before you tear the car apart to replace anything. The mag might be working but the wiring or switch bad and so you won't need to work on the magneto itself
Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Michael Garrison - Rice Minnesota on Saturday, August 06, 2016 - 10:59 am:

Also, (boy, I'm out of my element here) keep in mind that an ammeter isn't hooked up to a negative/positive wiring scheme. Both posts are hooked in-line into the feed from the generator to the switch. It's possible to hook it up backwards so the current flows through the gauge in the wrong direction.

Try to check the AC voltage coming out of the magneto post using an analog voltmeter. Clip the positive (red) lead to the magneto post and the black lead to a good ground. Then start the car on battery. The mag will show voltage output when the engine is running on battery. When the engine rpms are increased the magneto voltage will increase. I seem to have it in my memory that at increased engine speeds you can expect AC voltage in the 20 to 30 volt range.

Please someone with electronic knowledge chime in here. I'm really talking outside my area of expertise. Assuming of course I have an area of expertise.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Michael Garrison - Rice Minnesota on Saturday, August 06, 2016 - 11:02 am:

Phew, thanks Norm. My anxiety level has dropped considerably. :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Laughary on Saturday, August 06, 2016 - 07:41 pm:

Thank You

The brass peg of my Mag sensor fell off inside the hogshead, so I will drain the oil and try to fish it out with a camera. Only the spring came out when I removed it.

The new sensor is not putting out any voltage so far.

I will snake a camera in there and try to post pictures if the lens stays clean enough to see anything.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dan Jensen on Saturday, August 06, 2016 - 08:55 pm:

Sometimes this happens. Not good.

Magneto coil

Some of the magneto posts are just the spring with no brass peg. The one in my car was an older accessory oiler to the front, and was just a piece of wire like a thin corkscrew.

If you even for just a moment put the 6 volts DC to the magneto it will discharge the magnets. They can be recharged in the car.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Stephen D Heatherly on Saturday, August 06, 2016 - 09:22 pm:

Chris, the new switches are junk. If I were you I would take the original switch apart and see what's wrong with it. More than likely you would be able to fix it and parts are available.

Stephen


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dan Treace, North FL on Saturday, August 06, 2016 - 10:03 pm:

Chris

With a bright light you can spy the 'solder pad' on the field coil right, that is where the AC voltage is obtained by the contact.



Wear can dislodge that solder pad too. No voltage can then be obtained. The newer spring loaded contacts can be too long, and need to be ground down to trim the length, otherwise the contact can't be screwed down to fasten on the hogshead.



Many times the switch is the culprit, but with a bad contact loosing its point, that something to fix first. Then try again with the magneto volt test using a 1156 tail lamp bulb. That will tell if the magneto is working.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Laughary on Saturday, August 06, 2016 - 11:03 pm:

Thank You all!

I will post pics after this busy weekend with work and family.

My test light is also safe to use again, right? It did no damage in June.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Doolittle on Sunday, August 07, 2016 - 08:02 am:

Chris, assuming your "test light" is the #1156 Bulb in the Regan drawing above, the bulb should not be re-usable. Reason- if a magneto is a functioning properly---the bulb blows when the engine revs, making a blub that is no longer useable.

So, if you tested with the bulb in June, and the bulb glowed, but did not blow the bulb, then your magneto was not functioning properly at that time.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Doolittle on Sunday, August 07, 2016 - 09:10 am:

View this video for a demo.

https://youtu.be/cJZoUWLbex4


Top of pagePrevious messageNext messageBottom of page Link to this message  By Terry Horlick in Penn Valley, CA on Tuesday, August 09, 2016 - 07:30 pm:

On a tour in my 1913 once the engine was running on magneto when it sputtered and died. It ran fine on battery. When I got home from the tour I found that a nut in the switch had vibrated loose and shorted the switch to battery.

I fixed the switch but the magneto was still dead. The switch short had caused all the magnets to become de-magnetized. After an in-car magnet recharge it ran fine on magneto (I use my arc welder to charge my magnets). The mag remained good until I sold the car (well, longer than that... they are still good).

So if you clean the contact post and check the switch, it doesn't necessarily mean the magneto field coils are damaged. When you run the engine de-magnetized magnet can give zero current, or they can produce a very low current. What I am getting at is a magneto failing tests may not need the engine pulled, try a magnet recharge first. If you know how to do it a recharge is quick and easy do. Caveat emptor: if you have field coil buggered and shorted to ground your ohmmeter will show continuity to ground as normal and it is possible to make sparks inside the engine causing massive bursts of excitement.

TH


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Laughary on Tuesday, August 09, 2016 - 08:22 pm:

Thank You

Soon I will post Pics and more details


Top of pagePrevious messageNext messageBottom of page Link to this message  By keith g barrier Savannah Tn. on Thursday, August 11, 2016 - 10:48 am:

My opinion for what little its worth, If you have never had the engine apart and don't know the person you bought the car from then any model T engine is a pig in a poke. When all the simple checks have been made to no avail then time to pull the engine. If I buy a T engine that has a non working mag that's reason enough for a tear down. If everything flys apart then you can easily ruin an engine and more. I have an 26/7 engine here now that was rebuilt, no working mag, no safety wire, rods not shimmed properly. KGB


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Doolittle on Thursday, August 11, 2016 - 03:03 pm:

You are DEAD-ON Keith!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Thursday, August 11, 2016 - 03:54 pm:

I was on the Texas T Party tour one year. A guy had installed a distributor on a nice T that had no MAG. He was going pretty fast when a piece of angle iron "slinger" came through the side of the hogshead. Big mess.


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