24v ignition coil

[downhillbiker]

I'm realizing these are hard to come by. The person that owned my m211 before me converted to 12v, bit I want to take it back to 24v.

Is the 24v ignition coil for an m35 the same as what I would need for the m211?

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[dmetalmiki]

A 24 volt coil is a 24 volt coil. So you have plenty to choose from on the usual sites like -bay amaz-- and more. mostly around 30 or 40 bucks.

 

[73m819]

My thoughts on this

I was looking for a 24v coil for Swisses m62, the original died (broken winding), I put a nos one on, it died about 6 months, so went looking for a NEW 24v coil, I found out after talking to about 1/2 dozen people into the know including Delco that new 24v coils are not made anymore and any new coil that is found will be nos. The problem with a nos coil is the O in nos, as the coil sits on the shelf for years because of the low demand for a 24v coil, it sweats in the SEALED case due to the change in temperatures over time, this causes condensation which in turn causes rust, which causes deterioration of the windings, which causes early failure, in another words nos will be a waste of money. So knowing that points do not care if the voltage is 12 or 24, and finding out that a NEW 12v coil for a chevy 250 6 had almost the same output as the oem coil, a NEW 12v coil was installed and a separate ignition circut, that was 2 plus years with no problems.

 

[USMC 00-08]

How did you install the separate ignition circuit for the 12v coil?

 

[Crazyguyla]

The "24 volt coil" is just a regular 6 volt coil. The resistor drops the voltage from 24 to 5-6 volts. I was able to get a Bosch coil for VW air-cooled bug to physically fit, but the secondary tower was a little tall. Take the old coil to NAPA to find a match. The question is whether the coils have an internal resistor.

 

[73m819]

How did you install the separate ignition circuit for the 12v coil?

I took off from one battery, ran the power though a military dash flip switch to the points then the coil, this was a temp install that still is installed, I have a 24v relay that I planed to run the power though then to the flip switch, this will cut all power when the dash master was off, at least that was/is the plan.

Side note, I had already installed a separate ignition dash flip switch because the gassers use a single master dash flip switch to engage the master power realy, this powers EVERYTHING including the ignition, this makes it hard to work on the electrical system without taking the chance of burning the points, the second dash switch delt with the point issue.

 

[73m819]

The "24 volt coil" is just a regular 6 volt coil. The resistor drops the voltage from 24 to 5-6 volts. I was able to get a Bosch coil for VW air-cooled bug to physically fit, but the secondary tower was a little tall. Take the old coil to NAPA to find a match. The question is whether the coils have an internal resistor.

What I found out was that everyday 6v and 12v coils will not work because the windings are not as thick as the 24v version, this means that 6/12v coils will burn the winding up rather fast. I am guessing that you could use a 24v coil on a 6v/12v system but not the other way around (6v has thinner windings then 12v.

 

[Crazyguyla]

What I found out was that everyday 6v and 12v coils will not work because the windings are not as thick as the 24v version, this means that 6/12v coils will burn the winding up rather fast. I am guessing that you could use a 24v coil on a 6v/12v system but not the other way around (6v has thinner windings then 12v.

12v Hi-perfmaance coil with internal resistor? Heavy truck coil from that era? I really can't seeing Delco making a special coil for such a small market and not use something off the shelf.. I'm going to try using my Bosch coil since I'm pretty sure the current coil is bad. It tests good cold, but the ignition acts bad once warmed up and under load.

 

[m38inmaine]

You can retain the 24v system and still use the 12v coil, just run the ignition/coil hot wire to a 24-12 converter. I don't think the coil draws many amps so one could be had pretty cheap. By doing this you won't place an unbalanced load on your batteries.

 

[73m819]

12v Hi-perfmaance coil with internal resistor? Heavy truck coil from that era? I really can't seeing Delco making a special coil for such a small market and not use something off the shelf.. I'm going to try using my Bosch coil since I'm pretty sure the current coil is bad. It tests good cold, but the ignition acts bad once warmed up and under load.

At the time the market was quite high, most vehicles in the military were 24v gassers, a lot of cranes and other heavy equipment, big compressors, big gen sets, ect, ect was powered by 24v gassers, the 6602 that is in the early 5ts as well as other heavy over the road truck engines were 24v , when there was no more need for the big torque monster gassers and gone from the scene, the 24v ignition system went with them.

Yes, you have a bad winding, closes when cold, expands when hot there by breaking contract.

 

[pjwest03]

I would believe that it's just a matter of the right ballast resistor. The old ballasts for 12v systems are about 1.5 ohms. 3 of those in series would work, a bit ugly perhaps. Or a 300 watt wire wound resistor between 4 and 5 ohms would also do the trick. They can be had from Mouser or Digikey for $20-$30.

Now, if its a true 12v coil that doesn't use an external resistor, you would want more like 2-3 ohms.

 

[Kaiser67M715]

I'm subscribing to this thread, I have an m35 that has issues staying running on low idle trail runs, I think from the lack of airflow, and thus the coil gets too hot. Could be something else, but typically a 10-15 minute wait gets it to run again.

PS, the early deuce and the M35 and M54 (5ton) use the same coil, and many of the internals are the same too, distributor body and shafts are different.

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[Kaiser67M715]

[/COLOR]

At the time the market was quite high, most vehicles in the military were 24v gassers, a lot of cranes and other heavy equipment, big compressors, big gen sets, ect, ect was powered by 24v gassers, the 6602 that is in the early 5ts as well as other heavy over the road truck engines were 24v , when there was no more need for the big torque monster gassers and gone from the scene, the 24v ignition system went with them.

Yes, you have a bad winding, closes when cold, expands when hot there by breaking contract.

A lot of big rig trucks had 24volt electrical too, Mack especially used 24 starters and ignition in their gas motors, lights and other accessories where 12volt. That was during the 60's and 70's. Although none of the coils I've found would work, they are like a coffee can size coil with heat fins on them.

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[Crazyguyla]

The point I was trying to make is, the voltage at the coil after passing through the resistor is six volts. All automotive coils run at six volts. 12 volt automobiles either have a resistor/resistor wire that drops the voltage to six volts or the coils have an internal resistor. Even modern car electronics run 5-6volts, some things never change. Not all coils are made the same, some windings are thin, while other windings are a bit more hardier. As I stated earlier, I can't see Delco making a special coil for the military. It's just labelled 24v because that is the input voltage before it is reduced by the resistor to 6 volts. I have a couple of coils laying around that I know to be acceptable and will try them in my Duece. I'll let everyone know how it goes with firment and longevity. To bad it'd be really expensive to convert to coil on plugs and really have a more reliable system.

 

[DUUANE]

Ballast resistors are crap..i just wired my dodge CT800 up with a gm hei module and an internal resistor coil. No more ballast resistor no more magic box woes..ill try and get a part number off it..

 

[Crazyguyla]

Distributor breakdown

Since I was having trouble with my distributor, I decided to tear it down. Here's a picture from the manual labeling all the components. The primary lead passes through a capacitor and the coil has a capacitor. Both capacitors are for radio noise suppression and shouldn't affect the operation distributor. The resistor drops 24volts to 6 volts. Everything else runs like a normal points distributor.



Here's my distributor after I removed it from the engine. It's really gross and dirty. The vent lines were disconnected and moisture made its way in.



Here is it torn down. I was afraid the centrifugal advance weights were frozen, but they moved freely. I cleaned and lubed everything. I tried to remove the coil capacitor, but it's corroded in there. It's not worth destroying it to get it out. I'll work on getting it out another time. It took a couple taps from a rubber mallet to remove the coil. There's a rubber packing/gasket under the coil to provide a water tight seal.


Short in the primary lead, could be reason for poor running.



Soldered a new lead onto the capacitor. Not the easiest thing I've ever done.



Points are cleaned and gapped, distributor has been static timed. Have to recharge the batteries and see if I put it all together right.

 

[Crazyguyla]

What I found out was that everyday 6v and 12v coils will not work because the windings are not as thick as the 24v version, this means that 6/12v coils will burn the winding up rather fast. I am guessing that you could use a 24v coil on a 6v/12v system but not the other way around (6v has thinner windings then 12v.

This is what I have read about 24v, 12v, and 6v ignition coils. Some of this information is from other vehicle websites.

M37, M38, M151 use a 24v coil, no external resistor

2.5 and 5 tons use a 12v coil, external resistor drops voltage from 24 to 6 volts approximately.

Primary winding resistance in ignition coils:


From TM 9-4910-736-14&P, Ignition coil - capacitor tester
24v: 7 ohms (Delco-Remy 1115282)
1.5ohms (Autolite/Prestolite 115049, Delco-Remy 1915992) 12v?

From Google searches:
24v: 11 ohms approximately
12v (internal resistor): 3ohm approximately
12v (external resistor): 1.5ohms approximately
6v: 1.5ohms approximately

Besides the gauge of the windings, the 6volt coil has more secondary to primary windings than the 12v coil.


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