Mag Repair
Posted: Sat Sep 03, 2022 4:30 pm
After running Rusty, my 1927 roadster pickup, on a mag expertly rebuilt by RV Anderson about 25 years ago he suddenly refused to run on mag. Generally when this happens my go to solution is an in-car mag recharge. This is actually a magnet recharge and when the problem is a short of Bat. to Mag. caused by a flakey ignition switch it always works (after cleaning out and repairing the switch). Much to my dismay it this remedy completely failed.
My second string solution is to run on battery until something more life shaking occurs. This happened about a week ago and so when Rusty started losing power and making a horrible knocking noise I decided to just pull the engine out and have a look. First try was to check the rod bearings... all was well there. Next I found the problem, a blown head gasket.
Since the engine is out now is the time to figure out why the mag is putting out a fraction of the AC voltage it used to do. After a lot of head scratching and chasing after the problem with my VOM I finally hit upon a solution... I pulled all 4 mags I had accumulated at swap meets, arrayed them on the floor and went about testing in order to find the "new" mag for Rusty... none of them were good! So the next step was to chase down where the short is. Using my 2A 6V/12V charger I energized the original Anderson rebuilt mag and chased down which coils were energized.
I was having difficulty because several poles on the field casting had developed strong magnetism over the years. After much trial I finally figured out my method. I connected the negative wire to the engine block and touched the positive to the edge of the copper ribbon coming out of the first coil. The compass told me that coil was fine by getting excited.
I proceeded to move on to the second coil, which was likewise good. Working my way around the field I was able to find one coil which was bad. In fact the mag had been running on 4 functioning coils and 12 dead coils!
Next I pried the coil gently from the field casting so it lifted about a millimeter or two. Suddenly that coil was good again and in fact the whole mag came to life! The dead mag was a short on that one coil!. So what follows is the corrective procedure I have used:
I pulled a gallon milk jug out of the trash and using scissors I made two washers as shown.
The first washer is inserted between the coil and the casting.
The second washer is placed with the slit on the opposite side from where the slit on the first washer is located.
The mag is again tested with the battery charger. All 16 coils were now functioning so I proceeded pushing the coil back down to place with hand pressure. I again tested the mag with the charger and compass and found that the mag is now functioning as it should.
Time to get on to locating a replacement head gasket so Rusty can get back into the game!
Respectfully submitted, Terry Horlick
My second string solution is to run on battery until something more life shaking occurs. This happened about a week ago and so when Rusty started losing power and making a horrible knocking noise I decided to just pull the engine out and have a look. First try was to check the rod bearings... all was well there. Next I found the problem, a blown head gasket.
Since the engine is out now is the time to figure out why the mag is putting out a fraction of the AC voltage it used to do. After a lot of head scratching and chasing after the problem with my VOM I finally hit upon a solution... I pulled all 4 mags I had accumulated at swap meets, arrayed them on the floor and went about testing in order to find the "new" mag for Rusty... none of them were good! So the next step was to chase down where the short is. Using my 2A 6V/12V charger I energized the original Anderson rebuilt mag and chased down which coils were energized.
I was having difficulty because several poles on the field casting had developed strong magnetism over the years. After much trial I finally figured out my method. I connected the negative wire to the engine block and touched the positive to the edge of the copper ribbon coming out of the first coil. The compass told me that coil was fine by getting excited.
I proceeded to move on to the second coil, which was likewise good. Working my way around the field I was able to find one coil which was bad. In fact the mag had been running on 4 functioning coils and 12 dead coils!
Next I pried the coil gently from the field casting so it lifted about a millimeter or two. Suddenly that coil was good again and in fact the whole mag came to life! The dead mag was a short on that one coil!. So what follows is the corrective procedure I have used:
I pulled a gallon milk jug out of the trash and using scissors I made two washers as shown.
- Insulator washers
The first washer is inserted between the coil and the casting.
- Single washer
The second washer is placed with the slit on the opposite side from where the slit on the first washer is located.
- Second washer
The mag is again tested with the battery charger. All 16 coils were now functioning so I proceeded pushing the coil back down to place with hand pressure. I again tested the mag with the charger and compass and found that the mag is now functioning as it should.
Time to get on to locating a replacement head gasket so Rusty can get back into the game!
Respectfully submitted, Terry Horlick