how to test a coil ??

[Mike mandry]

Ive got a points ignition & need to check the coil (off the saw)

Can anyone lead me in the right direction.

I installed an atom module & still have no spark.

I suspect the coil is bad, but dont know how to test it.

Thanks

 

[no longer collecting]

coil test

pretty simple......you need a ohm meter tester. the coil has 2 windings....a primary and a secondary. the windings are connected together on one side to the ground on the armature with a screw (common wire). connect one side of tester to common wire and other side to small coil wire which is going to the points....you should have some resistance then you do the same with secondary winding....connect one side of tester to common wire and the other side to spark plug wire...you should have resistance.if both windings shows resistance...the coil is good..if one shows an open loop condition, the coil is bad. usually the spark plug winding side is the one that goes bad since it is affected by vibration and moisture if the coil is cracked.....hope this help.

 

[Mike mandry]

Thank you for simplifying that for me.

It is open from the plug wire to ground & has some resistance from ground to the connection where the points connect.
I guess its a goner.

Mike

 

[ray benson]

Hi Mike,
I have run across several coils that read that way and it was the plug wire open\bad. Replaced the plug wire and they worked.

 

[scottr]

Mike , it's also important that the winding does not have a low resistance or a short to the laminated iron core , the reading should be open .

 

[Mike mandry]

Pulled the plug wire out. Plug wire is open.

Its also still open from the plug wire connection on coil to ground.

What are the odds of that....

 

[scottr]

Mike , is the magnet wire (coil winding) connected by a soldered joint or a crimp to a pin ? If so it could be cracked or burnt open .

 

[Big feller]

To give an idea of the Ohm meter readings you should expect from a good coil I did a check on a spare from an 045.

Primary (low tension) side read 1.6 ohms.
Secondary (HT) read 5600 ohms.

I hope this helps.

Big feller.