Hot coil - hugh
I seem to burning coils out. Can anyone help explain what is going on.

I have a 1275cc engine fitted in a morris minor. I am now on my thrid coil. The last coil and the new one run very very hot. The car develops a misfire and eventually stops. This is cured by a new coil. I have 2 connections to the +ve terminal and one to the negative. Someone suggested that some new coils are low voltage coils, that require a ballast resistor to remove 3 odd volts. However they tend to have a live wire linked to the starter circuit to aid starting. Could it be that I have this fitted, but no resistor?

If so how are coils rated, how do I ensure that I get one that will cope?
Is there a way to check what sort of coil is fitted now, and whether I have a ballast resistor fitted or not?

all help appreciated.

regards

hugh
Re: Hot coil - Andrew Bairsto
Without doubt you are overvolting
Re: Hot coil - hugh
Andrew,

what is the solution, get a high rated coil?
Or fit some sort of resistor in line?

thanks

hugh
Re: Hot coil - John Slaughter
Andrew's right - you almost certainly are using a coil designed for use in a car with a ballast resistor. Easiest answer is to go to a supplier and get a 'genuine' 12V coil - one designed for use directly on the system. Any MM parts supplier will help. Mail if you need contact numbers.

Cheers

john
Re: Hot coil - Andrew Bairsto
You need the choke to hang the handbag on
Re: Hot coil - John Slaughter
I think you're confusing this with heating up your Carmen rollers!

Cheers

john
Re: Hot coil - hugh
Thanks all for the advice, I fitted a 12V non-ballasted coil last night. Took the car for long thrash, and the coil was warm but not hot. Driving 50 miles this morning, no problem. Also checked the A+ 1275 used a ballasted coil, but I dont have all the electrics around it.

thanks again for the quick response.

hugh
Re: Hot coil - Andrew Moorey (Tune-Up Ltd.)
Coils for your car can be broken into two groups; Ballasted or non-ballasted. A coil for a ballast system will be rated at approx 1.5 ohms, non ballasted at around 3 ohms. Measure this across the LT terminals. With your voltmeter measure the voltage at the positive side of the coil with the points closed. If your car is fitted with a ballast resistor it will be 6-8-volts. If battery votage is present then you will need to fit a 3 ohm, non-ballast coil, sometimes called a "standard" coil. You say that you have two wires on the + side, this would indicate that a ballast-bypass wire from the starter solenoid is fitted. This "boosts" the voltage available at the coil during cranking to give a bigger spark. This is easily tested by disconnecting the wire from the ignition switch at the coil and having an attractive assistant crank the motor over whilst you check for a spark from the ignition coil. If the bypass is fitted and working then you should get a spark while the engine is cranking. This will tie in with a 1.5 ohm coil. Many modern coils are only rated at .5 ohm or less. These are for electronic ignition only.
Hope I haven't confused you,
Good luck
Andrew.
 

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