i have an 85 xj6 and the battery light stays on even though it has a good battery is this a short and where am i most likely to find this short?
i have also noticed the coil has a ballast resistor which is obviously getting hot and smoking, i went to advance they say my car should not have a ballast resistor the only coil they have for my year does not use an external resistor is it ok to replace the existing coil and resistor with this one?

It could be that your alternator has failed.

Or it could be as simple as as broken or loose alternator belt.

Also check the wiring at the alternator. The small "excitor" wire is known to come loose or break.



Some did, some didn't.



Yes, it should be no problem, so long as it is a 12v coil with about 1.0 hm primary resistance....which is an almost generic specification.

Cheers
DD

I suggest buying a pertronix coil off amazon. $30 free shipping and they are awesome! smoother idle just about guaranteed.

Is the battery being charged with the warning light on, or is it not actually charging?

Not being charged...or not fully charged.

Cheers
DD

As in my case, the battery light was on but the alternator was overcharging. Connect a volt meter to the battery and verify whether the alt is charging or not. This should be the first step. If it is charging you should get a reading of 14+ volts. With a good reading and the light on, check the single wire on the alternator that goes to the light.
if the voltage is just battery voltage, then start looking at the alternator. Remove and clean all connections, positive and negative. Ask me how i know this. Those old wires reek havoc on these cars.

Good point!

I should've allowed for that possibility in my answer


Cheers
DD