Mag questions

Discuss all things Model T related.
Forum rules
If you need help logging in, or have question about how something works, use the Support forum located here Support Forum
Complete set of Forum Rules Forum Rules
User avatar

Topic author
Rata Road
Posts: 172
Joined: Mon Mar 25, 2019 11:58 am
First Name: Kevin
Last Name: Weeds
* REQUIRED* Type and Year of Model Ts owned: 1923 Depot Hack, 1927 Coupe & 1914 Runabout
Location: New Zealand
Board Member Since: 2015

Mag questions

Post by Rata Road » Tue Aug 16, 2022 5:26 am

I have a friend with a 13 (no starter or generator) with Mag issues.
History -Restored in Virginia in the 80's and stored in a controlled garage with very little use. Imported to NZ 2015 and only done a few miles since.
Last year it wouldn't run (even idle) on Mag at all. We recharged the Mag in the car and now it runs but not a smooth as when on a 12v battery.
I'd appreciate your opinion on the following points

1. If the Mag was rebuilt in the 80's would it lose its performance from sitting or does driving it wear them out?

2. We lifted the Mag from zero output to running the engine from the in car charge do you think it would it be worth having another go at charging in the car or is it common practice to pull them out if the first attempt doesn't fix it completely.

Thanks


Philip
Posts: 238
Joined: Sun Jan 06, 2019 12:09 pm
First Name: Philip
Last Name: Thompson
* REQUIRED* Type and Year of Model Ts owned: 1924 touring
Location: Graham NC

Re: Mag questions

Post by Philip » Tue Aug 16, 2022 7:42 am

i would try recharging again with more power. use more batteries


Kerry
Posts: 1297
Joined: Mon Jan 07, 2019 2:42 pm
First Name: Frank
Last Name: van Ekeren
* REQUIRED* Type and Year of Model Ts owned: 1916 touring, 1916 pick-up, 1924 coupe, 1926 touring, 1927 touring
Location: Rosedale Vic Australia

Re: Mag questions

Post by Kerry » Tue Aug 16, 2022 7:59 am

Check what voltage the mag is putting out, it might be ok and your coils need tuning.


TXGOAT2
Posts: 6411
Joined: Sun Feb 14, 2021 10:08 pm
First Name: Pat
Last Name: McNallen
* REQUIRED* Type and Year of Model Ts owned: 1926-7 roadster
Location: Graham, Texas
MTFCA Number: 51486
Board Member Since: 2021

Re: Mag questions

Post by TXGOAT2 » Tue Aug 16, 2022 8:04 am

A magneto shouldn't lose much, if any power, while sitting. Running the car does not necessarily deplete them, either. What does affect a Ford magneto in service is the air gap between the stator and rotor, and it will get larger as the engine bearings wear. Any wiring problem that applies battery current to the magneto will damage it by de-magnetizing the magnets. Magneto output can be tested using an AC voltmeter to determine if the magneto is at fault or not. Other likely causes of starting issues would be the condition and adjustment of the coils, the timer, and any and all connections in the ignition circuit, including internal contacts in the ignition switch and any of the electrical grounding points. Recharging the magneto, assuming it needed recharging at all, could mask problems with coil adjustment, or the condition of the points, capacitors, etc, or issues in any of the wiring, coil box contacts, etc. A magneto output test would reveal whether it is the primary problem or not. If a test indicates that magneto output is deficient, it could be due to weak magnets, or excessive air gap caused by excessive main bearing thrust face wear, or a poor contact at the magneto output post, or a problem with the magneto windings.


TXGOAT2
Posts: 6411
Joined: Sun Feb 14, 2021 10:08 pm
First Name: Pat
Last Name: McNallen
* REQUIRED* Type and Year of Model Ts owned: 1926-7 roadster
Location: Graham, Texas
MTFCA Number: 51486
Board Member Since: 2021

Re: Mag questions

Post by TXGOAT2 » Tue Aug 16, 2022 8:05 am

Cars in storage often develop fuel system issues.


speedytinc
Posts: 3840
Joined: Fri Feb 12, 2021 12:24 pm
First Name: john
Last Name: karvaly
* REQUIRED* Type and Year of Model Ts owned: 14/15 wide track roadster. 23 touring, 27 roadster pickup, 20ish rajo touring
Location: orange, ca
MTFCA Number: 14383
Board Member Since: 2020

Re: Mag questions

Post by speedytinc » Tue Aug 16, 2022 8:14 am

First check mag output voltage. If weak, a hotter charge, 36v or best a high output dc arc welder. Second clean/check coil points. They will oxidize over time. Check the tune on the coils.


Norman Kling
Posts: 4070
Joined: Tue Jan 08, 2019 1:39 pm
First Name: Norman
Last Name: Kling
Location: Alpine California

Re: Mag questions

Post by Norman Kling » Tue Aug 16, 2022 9:37 am

First do this small things to help determine just what is wrong.
1. Measure out voltage with an AC analog voltmeter at the terminal on hogs head to chassis ground. A light bulb parallel to the meter will help. It should be at least 6 volts at idle and increasing as you rev the engine. Can get up to 20 volts approximately at higher RPM. If this test is OK (especially at idle) your Mag is OK. If not, the magnets need to be charged. Best charge would be with the hogs head off and each magnet charged individually. Remember that they alternate in polarity, with two positive poles together and two negative poles together, so use a compass to determine the polarity. The North pole of the compass points to the south pole of the magnet.
2. Check for end play in the driveshaft. When you push down the pedal to neutral or low, the crankshaft will be pushed back by the spring in the clutch. when it is in high gear, the crankshaft will be allowed to move forward, so first push down the clutch and then let it into high gear with the brake off. Try to pry the crankshaft forward at the front pulley If it moves noticeably you have a worn thrust surface at the rear main bearing. This must be repaired to keep the proper clearance between the magnets and the coils.
If the magneto checks out OK, the next check would be the current drawn by the coils. They should be set to spark at 1.5 amps. The closer you get each coil to spark at the same current, the smoother the engine will run, especially when on mag, because the voltage builds up on the magneto the coil sparks. If one coil takes more current, it will fire later on the mag cycle than another which draws less current. When you run on battery, the coil will fire whenever the timer rotor contact, so the engine will run smoother, with mis-aligned coils but will have less power.
The book published by the club "Electrical System" explains with illustrated pictures, how to do most of the things I have stated above.
Norm

User avatar

Topic author
Rata Road
Posts: 172
Joined: Mon Mar 25, 2019 11:58 am
First Name: Kevin
Last Name: Weeds
* REQUIRED* Type and Year of Model Ts owned: 1923 Depot Hack, 1927 Coupe & 1914 Runabout
Location: New Zealand
Board Member Since: 2015

Re: Mag questions

Post by Rata Road » Tue Aug 16, 2022 5:26 pm

Thanks guys some great suggestions there.
I'll try and get a Mag readout next time he plans to start the car as from what your saying that would clarify the mag output. Its a good starter off the crank and runs smooth on Battery so I doubt its a fuel issue.
Maybe a coils clean up and check is also on the cards.

Thanks again

[attachment=0]1672397938.jpg[/attachment]
Attachments
1672397938.jpg

User avatar

AndreFordT
Posts: 487
Joined: Sun Jan 06, 2019 12:25 pm
First Name: Andre
Last Name: Valkenaers
* REQUIRED* Type and Year of Model Ts owned: 1926 ; 1922 ; 1915.
Location: Scherpenheuvel
MTFCA Number: 23792
MTFCI Number: 19330

Re: Mag questions

Post by AndreFordT » Tue Aug 16, 2022 11:31 pm

Norman is so right with his advice to check the magnéto and coils but I would like to add this to the comment.

Sometimes the reason of not good or not at all working of the magneto is brake band debry between the magneto coils.
See photos.

Good luck.
Andre Belgium
Attachments
DSCN6931.JPG
RSCN6922.JPG
RSCN6921.JPG
RSCN6920.JPG
during a test with the coil loop out of the engine after a magneto failure. The coil loop was rebuild a few months before.
during a test with the coil loop out of the engine after a magneto failure. The coil loop was rebuild a few months before.

User avatar

Steve Jelf
Posts: 6463
Joined: Fri Jan 04, 2019 9:37 pm
First Name: Steve
Last Name: Jelf
* REQUIRED* Type and Year of Model Ts owned: 1923 touring and a few projects
Location: Parkerfield, Kansas
MTFCA Number: 16175
MTFCI Number: 14758
Board Member Since: 2007
Contact:

Re: Mag questions

Post by Steve Jelf » Wed Aug 17, 2022 12:17 am

I can't improve on the excellent posts by Pat and Norm, but I'll add a little more information. The absolute best magnet charge is done with the magnets out of the car and off the flywheel, one at a time individually. When I do this the magnets hold 4½ pounds or a little more (the traditional test weight given in the Electrical System book is two pounds). I have read that an in-car charge gives about 60% of a full charge. That should be sufficient for good running if all the other electrical components are up to snuff.
The inevitable often happens.
1915 Runabout
1923 Touring


Norman Kling
Posts: 4070
Joined: Tue Jan 08, 2019 1:39 pm
First Name: Norman
Last Name: Kling
Location: Alpine California

Re: Mag questions

Post by Norman Kling » Wed Aug 17, 2022 1:02 pm

I agree with Steve, especially if the engine is out of the car and a complete rebuild of the magneto is needed or desired. You can also adjust the height of the magnets above the surface of the flywheel. You can also test and replace any broken magnets that way. And you can adjust the distance of the coil ring from the engine to get best adjustment of everything. However, if all you want to do is charge the magnets without pulling everything apart, you can get a better charge by pulling the hogs head and charging each magnet individually. You can also check for spacing between the magnets and the coil ring and if it is excessive, you can then decide whether or not to pull everything out. I would suggest that if you do pull it, you repair or rebuild everything from the block to the universal joint so you won't need to do so as soon.
Norm

Post Reply Previous topicNext topic