24 volt coil

Cacti_Ken · Post by **Cacti_Ken** » Sat Jul 10, 2010 8:58 pm

Wes, I have two used coils. On both, the primary resistance is 12.5 ohms.
The secondary resistance is 10.10K and 10.15K ohms.

Referencing to your photo of the coil on a previous post shows primary resistance of 5 to 6.2 ohms. And secondary 9k to 12k.

My coils secondary resistance are in the tolerance range of your test. But the primary is twice as high as yours.

Could I take it that these coils are bad? Its peculiar that both of the coils measure practically the same.

Ken

Post by **wesk** » Sat Jul 10, 2010 10:38 pm

Ken,
What do your primaries ohm at when hot?

Cacti_Ken · Post by **Cacti_Ken** » Sun Jul 11, 2010 12:34 pm

I don't know Wes. I got the coils during my restoration and kept them for spares.

Is it ok to apply 24 volts to them for a short period maybe 15 to 20 seconds and check the resistance? Or best to put them in the distributor and run them assuming they are good to run.

Post by **wesk** » Sun Jul 11, 2010 4:52 pm

You just heat the coils with a hair dryer or heat gun until they just start to get uncomfortable to touch or hold. Then measure their resistance.

maeserik · Post by **maeserik** » Tue Jul 13, 2010 4:49 am

I have a spare 24 volt coil, i will measure the resistance this evening, i let you know.

Erik

maeserik · Post by **maeserik** » Wed Jul 14, 2010 4:40 am

I checked the coil, i have two M151 coils also 24 volt and same dimensions.

primary 12,8 ohm

secondary 12k ohm

cold measured on a spare one ( same as in use on my38 )

as info :
i use a mutt m151 coil in my distributor together with the swiss solid state ignition all on 24 volt

Cacti_Ken · Post by **Cacti_Ken** » Wed Jul 14, 2010 4:34 pm

I heated up the coils and the restistance only changed 3/10ths of an ohm.
Maybe different manufactures had different turns ratios in their coils

Ken

Wiltshireboy · Post by **Wiltshireboy** » Fri Jul 16, 2010 1:09 am

Does anyone know what amount of change of resistance on the primary and secondary windings from cold to hot indicates that the coil is not good?