snajar

I replaced the original ignition coil on my 2000 Honda Civic (due to a no spark) with an after market part. The failed coil on my Ohm meter read:

Malfunctioning Coil on 2000 Honda Civic:
Primary Winding (A and B Terminals): 1.1 Ohms
Secondary Winding (A|B and Spring): 9.9K Ohms


New After-Market Coil on 2000 Honda Civic:
Primary Winding (A and B Terminals): 1.0 Ohms
Secondary Winding (A|B and Spring): 14.24K Ohms

Question: Why would a 4.34K Ohms difference cause a complete fail instead of a gradual/partial fail?

tony_2018

not the engineers who build the the civic to these specs.....best find them and ask them.

mk378

Ohm testing a coil is kind of a useless endeavor. Coils can ohm OK and not fire. On the other hand, if you have one that ohms out of spec, it's certainly bad.

This is because the high voltage side is made out of many turns of fine wire. One turn shorting to the next one will decrease ohms by an almost unmeasurable amount, but it is an AC short that will sap all the energy out of the coil instead of going to the plugs. You will only get weak sparks that usually don't make it past the rotor and cap.

The real test is to take the cap off, hold a grounded test wire about 1/2 inch from the coil output, and crank. You should get good strong blue-white sparks. If you have to move the wire closer and only see little yellow sparks, it's almost 100% certain that the coil is bad. If you don't get sparks at all there could be a different problem.

Never crank or run the engine with the coil facing an open circuit, this puts a lot of stress on the coil. Always have the system complete and hooked up with all 4 spark plug wires, or with a test wire for the sparks to jump to. When doing a compression test, unplug the low voltage wires to the distributor.