Help Understanding Points ... Few ?'s

[dtnodya]

OK, I'm working with an old Mac 1-10 and I'm not getting a spark. So It seems to me that it has to be either the coil or the condenser. I've cleaned everything, set the point gap. I am not very familiar with points at all but I think I have a 'clue'.

My questions:

To test the coil with a multimeter, do I set to Oms and connect to the wire that leads to the condenser and also to the 'ground' on the coil? And then connect to the end of the plug wire and to the ground? Checking for resistance at each one? Use 200k for the lead to the condensor and 20k going to the plug wire? I've read through a couple threads and want to make sure I understand that ... so if anyone can help with this It'd be appreciated.

Second question is .. Will any condensor work? I mean, if I can find one that is the same size from another saw (any saw) will it work for this Mac? Why or why not? Points are frustrating!!

Thank you all.

 

[bama]

If it is the condensor, could you just use an Atom module to replace the points and condensor? I have done this on many of my old briggs motors. Never tried it on a saw, yet, but sure would be willing if I had one fail.

 

[dtnodya]

What is an atom module?

 

[HiOctane]

What is an atom module?

Its a small electronic module that replaces points and condensor made by Atom company and others.Very easy to install.You must choose the right one because there are modules for chain saws,4 stroke engines,etc,all of different colors to recognize them.

 

[Jacob J.]

Sounds like you have the resistance test procedures down for testing your condenser. There are a number of condensers that will work in place of your OEM condenser. They have to meet a fairly similar resistance range and that's pretty much it (other than physically fitting under the points cover). The Atom solid state module does work very well on McCulloch saws and reduces the future maintenance needs for the ignition system.

 

[lesorubcheek]

I usually disconnect the lead to the points/condensor to check a coil, just in case there's a short, but yes, you're right on with the connections. Ground is common to both the primary and secondary in the coil (its just a transformer) and you should see a relatively low resistance (1-4 ohms or so)between the wire going to the plug and ground and a fairly high resistance (k ohm range) between the lead going to the points/condensor and ground. As for the condensor, its just a capacitor. If you have a meter that measures capacitance (farads, well actually mf) you can test the condensor too. The condensor should look like an open circuit with NO resistance. If the condensor shows resistance, its shorted and it'll need replacement. Again, make sure to remove its connections so its isolated from other electrical parts when testing.

Dan

 

[Al Smith]

Most of the times the problems is that the points are not completely closing .Also if closing,not passing current,because of a tiny piece of grit or corrosion.Burnish the points,then use a piece of lens paper to make certain no grit is caught between the points .Set the points at .018" and the coil air gap at .010" to .012" and chances are it should provide a nice blue spark.

In all the McCullochs I've ever worked on,I've only seen one points type coil ever go bad.I have seen several bad condensers though.For that matter I've only seen two Mac solid state coils be defective.I certainly cannot say the same for Stihl.

Oh,an after thought.In the area the coil mounts,shine up the metal of the coil plus the area on the saw case,to insure a positive ground connection.This normally does not corrode but it is possible.

 

[Lakeside53]

Condensors really need to be tested under stress (voltage). Multimeter capacitance testers don't do that (they just apply a known frequency and measure the resultant current). A true points condensor tester applies a few hundred volts at the same time.

I replace condensors on old saws regularly -much easier than the electronic "upgrade" in many cases.

 

[dtnodya]

Thanks for all the info! Andy, yeah I'm not trying to test the condenser, just wanted to make sure I had the coil process down. I didn't know about Atom solid state upgrades for saws with points (that crap out) ... learned somethin' new.

Al, I've cleaned the points, set them at what you recommended, set the coil/air gap also, but I will try to shine up where the coil mounts. The saw did/does have some oxide working on it.

 

[scottr]

I usually disconnect the lead to the points/condensor to check a coil, just in case there's a short, but yes, you're right on with the connections. Ground is common to both the primary and secondary in the coil (its just a transformer) and you should see a relatively low resistance (1-4 ohms or so)between the wire going to the plug and ground and a fairly high resistance (k ohm range) between the lead going to the points/condensor and ground. As for the condensor, its just a capacitor. If you have a meter that measures capacitance (farads, well actually mf) you can test the condensor too. The condensor should look like an open circuit with NO resistance. If the condensor shows resistance, its shorted and it'll need replacement. Again, make sure to remove its connections so its isolated from other electrical parts when testing.

Dan

Dan , you have the primary and secondary resistance readings reversed . The primary (points) is the low resistance and the secondary (plug) is the high resistance . It's also necessary to assure that non of the windings are shorted to the iron core laminations .

 

[lesorubcheek]

Dan , you have the primary and secondary resistance readings reversed . The primary (points) is the low resistance and the secondary (plug) is the high resistance . It's also necessary to assure that non of the windings are shorted to the iron core laminations .

Oops,
You're right Scottr... thanks for straightening that out. Proof that I haven't been spending enough time working on my saws lately. My apologies if I confused anyone.

Dan

 

[dtnodya]

Oops,
You're right Scottr... thanks for straightening that out. Proof that I haven't been spending enough time working on my saws lately. My apologies if I confused anyone.

Dan

You didn't.

. It's also necessary to assure that non of the windings are shorted to the iron core laminations .

What do you mean by this?? I'm a points :newbie:

 

[scottr]

You didn't.



What do you mean by this?? I'm a points :newbie:

dtnodya , the windings (magnet wire) is solid copper wire that has a thin insulation . If the insulation fails and allows the copper to touch the laminated iron core the coil will not work correctly . If there is a high voltage carbon path from the copper winding to the laminated iron core the coil will not work correctly . It's important to check with your ohmmeter to assure that the winding is isolated from the iron core .

 

[dtnodya]

dtnodya , the windings (magnet wire) is solid copper wire that has a thin insulation . If the insulation fails and allows the copper to touch the laminated iron core the coil will not work correctly . If there is a high voltage carbon path from the copper winding to the laminated iron core the coil will not work correctly . It's important to check with your ohmmeter to assure that the winding is isolated from the iron core .

OK, hopefully I'm not getting redundant ... So how do you test to see if the winding is isolated? I assume you test certain points (magnet wire and ???) with the coil off of the saw?? Or am I just confusing myself?

Thanks for the info and help. I like learning the technical crap behind stuff.

 

[Al Smith]

Very ,very rarely do the windings break down by moisture trapped with in the coil.I've never seen this on a saw mag but I have on a Wico mag coil of a John Deere B.If this be the case,stick the coil in an oven on real low heat,200 to 250 degrees maybe for several hours.After it cools give it a coating of clear urathane or glyptol[electical insulating paint] .This may or may not cure the problem.

 

[scottr]

OK, hopefully I'm not getting redundant ... So how do you test to see if the winding is isolated? I assume you test certain points (magnet wire and ???) with the coil off of the saw?? Or am I just confusing myself?

Thanks for the info and help. I like learning the technical crap behind stuff.

You measure the resistance of the primary side of the coil to the iron core and the secondary side of the coil to the iron core . You are looking for a open circuit .

Very ,very rarely do the windings break down by moisture trapped with in the coil.I've never seen this on a saw mag but I have on a Wico mag coil of a John Deere B.If this be the case,stick the coil in an oven on real low heat,200 to 250 degrees maybe for several hours.After it cools give it a coating of clear urathane or glyptol[electical insulating paint] .This may or may not cure the problem.

Al , member Lewis Brander has had a few coils with the problem .

 

[Al Smith]

Al , member Lewis Brander has had a few coils with the problem .

Yes I do believe he in fact did.I think they were Mall coils if I recall correctly,rare as a hens tooth.Luckily McCulloch coils are not.Any 10 series points type coil will fit that saw.

As it is,a lot of people have trouble with points type ignition system.I don't but perhaps it just goes with my age or something.

 

[dtnodya]

You measure the resistance of the primary side of the coil to the iron core and the secondary side of the coil to the iron core . You are looking for a open circuit .

Al , member Lewis Brander has had a few coils with the problem .

Thx for clearing that up. I see what you are saying now.

Yes I do believe he in fact did.I think they were Mall coils if I recall correctly,rare as a hens tooth.Luckily McCulloch coils are not.Any 10 series points type coil will fit that saw.

As it is,a lot of people have trouble with points type ignition system.I don't but perhaps it just goes with my age or something.

I did not know that any 10 series points style coil would work!!! Good info! I guess it would/might be easier to understand the points system if I had a saw that worked and then quit. Since I've never messed with points before and this thing doesn't have spark to start with, it's been seriously confusing. But you all have helped me understand this simple yet complex config ..

 

[Al Smith]

Check out this link,it explains every thing,in a way better than I can.Two parts,good stuff. http://www.foxvalleykart.com/timing1.html

 

[dtnodya]

Check out this link,it explains every thing,in a way better than I can.Two parts,good stuff. http://www.foxvalleykart.com/timing1.html

Great link!!