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HI Guys, Can someone walk me thru testing a coil. using dig. meter, where do I put the setting 20m,2000k,200k,20k,2000,200. craftsmen#82015. Can I test with the coil out and not hooked-up? (I took it off the truck) the thread states 6. across (+ and -) secondary:14.5-15 ohms sec.test + lead on ctr. on coil and - lead to - term. of coil. anything else? let me know what setting. I have a autolite with no numbers does anyone know what coil to purchase if coil is bad. Thanks to all vinnytruck

Are you having a weak spark across the plug gap? It could be the condensor.

Anyways, I have had luck with an Accel coil and an MSD one. I think most any can style 12v coil would work, just make sure you have the ballist resister hooked up, or a healthy stock of condensors for the dizzy. That is assuming you're running a 12v system. 24v, you'll need to wait for one of those guys to roll through and pickup where I can't fill in.

Sorry guys for misleading...I have a 24V org. system in now is a autolite coil, I dont know if autolite was the org. coil??? vinnytruck

Hi Vinny,

I'm guessing your meter doesn't autorange......so primary side first. Make sure coil is not connected to anything. Set the meter to Ohms (the green section on the meter face) on the lowest setting (200 ohms I believe). Put one meter probe on the (+) terminal of the coil and the other probe on the (-) terminal. Meter should read around 6 ohms. Secondary side......set the meter to the 20K range. Positive probe goes to the center of the coil, negative probe goes to the (-) terminal on the coil. You're looking for a reading in the 15K ohm range. Get R Done brother!

later,
bob

OK BoB, Did that... (out of truck on my desk) prim= 12.2 second.= 10.49 Whats its saying? thanks bob,,,, vinnytruck

Hi Vinny,

I assume you mean the secondary is 10.49 THOUSAND ohms, right? I'm no expert on this stuff, but from what I read you want the primary at around 5 to 6 ohms and the secondary at 9000 to 12000 ohms. Your primary resistance is twice what it should be......so I think something is amiss. But hopefully someone on here with more electrical experience (Ed...you reading this?) can give you a better answer.

regards,
bob

Good Evening Bob, thanks for the reply. Its seems alittle off from what you said. Today I purchased a coil from AB LINN. I didnt want to spend for a coil but inorder to learn I purchased one. (really 2 incase I blow the first one up). Hope it comes soon to do my testing. You know that AB guy has always been in my corner since I started this M-ing...seems to be a fair guy. Tomorrow I will try to start the truck again in different ways, I will let you and the guys know how I made out. Yes I will try to take pictures, the last time my camera didnt charge...Gee maybe just like its owner. thanks as always, vinnytruck

Hi Vinny,

I've bought a ton of stuff off of AB and they parts are good, prices reasonable, and they deliver FAST. Never actually talked to anyone there, as I've always bought thru eBay.....but certainly no complaints with those folks.

regards,
bob

Vinny,

I finally got around to measuring two coils I have a new repop and an original. Here's what I got;

Repop Primary: 12.2 ohms
Repop Secondary: 10,000 ohms

Original Primary: 11.8 ohms
Original Secondary: 11,200 ohms

So.....unless both my coils are bad....your numbers sound about right.

regards,
bob

Hello Bob sorry I didn't reply sooner. I went thru several coils checking readings. Mainly due to the issue I had with my M37. read lots of post.Did a lot of digging. OK I'll get to the point, On the primary side you should
have 6 Ohms, on the secondary side you should have 14.5--15k Ohms. That's the info I got thru a lot of research. As mentioned I went thru several coils I had checking readings. They all were extremely close. I picked the best to install in my M.

Hi Ed,

Yeah, the numbers you say are what I read was correct too....but it seems a number of guys on here, and now myself, are seeing 12 ohms on the primary....and the coils are good. Not sure what's going on. And from what I understand about inductive coils doubling the input resistance cuts the time constant in half (a good thing), but lowers the total energy stored in the primary inductance by a lot (E=1/2 LI^2)...so it's exponential in regards to current. So I'm at a loss here....as to why so many of us are finding good coils with a primary resistance twice what it should be. Unless both my coils and Vinny's are bad.

regards,
bob

Here's an interesting thing I found. AB Linn has new 24V coils for M37, M38, etc on eBay and here's what the listing says:

"late style ignition coil ballast is made in the bottom of the coil no external resistor needed".

I didn't know the M37 had an external resistor. But adding a resistor would raise the primary resistance........just saying......

bob