Hi all I have a problem with my '72 clubman temp gauge and oil light when I disconnect positive wire to coil, gauge and light work and when I reconnect coil wire gauge and oil light stop working also when I reconnect coil wire I notice that the volts drop from 12 volts to around 10 V. Could I have the wrong ignition coil installed? it is a Bosch unit with the letters and number SU 12 stamped on the bottom of it. Any ideas out there?

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toolman

Hi & welcome! Rather than the Bosch coil being the wrong one, more likely it has high internal resistance & may be on the way out. Have u got anuther coil you can try?
Also, check all your connections at the fuse block, fuses etc for dirty connections. If its not the coil, sounds like you have high resistance in the wiring somewhere, or faulty earthing at the chassis.

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1967 Cooper S - new front bearings to do.
1965 Cooper S shell - Slow progress. No time or money!
1966 Deluxe- next rustoration!
Mk 2 & XJ6 Jags. Less said the better.

Just checked my spare coils - Bosch SU12 should work OK. If you can check the primary resistance, it should be about 3 to 3.5 ohms.

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1967 Cooper S - new front bearings to do.
1965 Cooper S shell - Slow progress. No time or money!
1966 Deluxe- next rustoration!
Mk 2 & XJ6 Jags. Less said the better.

THe coil itself is brand new only a couple of weeks old .I read somewhere something about coils with ballasts and non ballasted coils does anyone know which one goes with which mini?

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toolman

You may also have a bad connection upstream from the coil causing voltage to drop across it once some current is drawn.

With the symptoms you describe, I would maybe check the voltage coming out of the ignition switch to the switched fuse, but also check the 12 volt feed coming into the ignition switch as well. Perhaps there is hot joint at the solenoid stud, or a worn out contact in the ignition switch. In a nut shell the idea is to trace the low voltage upstream until you find the joint where it goes from 13(ish) volts to 10 volts with the COIL CONNECTED AS USUAL. It needs current draw to cause a voltage drop you see.
Also check the connections at the fuse block as well, they need to be nice and tight and clean.

Don't concern yourself with the ballasted coils, they are where a resistor is switched into circuit once the car is started to reduce the current draw to the coil and hence the spark intensity.

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SooperDooperMiniCooperExpertEngineering

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