Author Topic: Anyway to check an ignition coil with amulti meter?  (Read 306 times)

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Offline weimedog

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Anyway to check an ignition coil with amulti meter?
« on: January 22, 2014, 03:59:57 pm »
Title is the question.

Putting together a saw, two ignition's (used from the pile) and three spark plugs...no spark. Flywheel magnets still pull...

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Offline Cut4fun .

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Re: Anyway to check an ignition coil with amulti meter?
« Reply #1 on: January 22, 2014, 04:09:01 pm »
I know there was a thread on this here somewhere. Cant locate it to see if info you are wanting.

Jim showed me one time at my place testing coil. But I havent a clue what I am reading for good or bad. Just thinking I was seeing open closed ( I have no clue what I am talking about so take like grain of salt).

Some info toward middle bottom here.  http://www.madsens1.com/saw_ignition.htm

If I find the other coil thread I'll link it here.
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Offline 660magnum

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Re: Anyway to check an ignition coil with amulti meter?
« Reply #2 on: January 22, 2014, 07:13:30 pm »
The spark plug electrode to coil frame should have some resistance but it will read very high.

The points wire to ground, or the spade that goes to the switch and to ground should read a very low resistance.

The spark plug to the spade should have some resistance but should be almost irrelevant for it will be the some of the other two - the value of which will confuse you for it will be the sum of two fractions. 

The main thing to look for is that neither is shorted or open.

There are other ways to check a coil's integrity with a "high pot" but beyond the above observation, the important part is that the coil either works or doesn't particularly if it is a self contained coil that doesn't use points.

Coils with points, often the points do not conduct, the capacitor (condenser) is dried out, or there is a ground problem.

Also older coils and condensers prior to the early 60's have shellac and or bee's wax as insulators which could have too much moisture or the condenser dried out and cause them to not work properly. The epoxied or plastic covered coils most often get damaged by heat.

A capacitor (condenser) can be checked with a ohm meter also. It is a matter of having the capacitor isolated from the circuit. Short the two parts of the capacitor together to discharge it.
Then, hook to the circuit of the ohm meter which typically uses 9 VDC. At first, the capacitor will be charging and show almost a short but then as the capacitor becomes charged, the ohm meter will show a open circuit. If you have a digital ohm meter will be that the numbers change around a good bit before settling down. With a old needle type ohm meter, you will see the needle go high and then drop low. If you see no action at all on a previously discharged capacitor, it probably is not any good. 
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