Coil gets hot when key is on. Is this normal?

[71massbronco]

Still am struggling with timing, but noticed that the coil was getting warm when I would leave the key in the on position without the motor running. Is this normal or is the coil on the way out. BTW it ohm'd out OK when tested. Thanks.

 

[DirtDonk]

Yes. And it's why you're not supposed to actually do that when it can be avoided.
They even get too hot to touch sometimes when the engine is running, but at least then they have the benefit of some of the cooling air flowing over them.

Depending on the type of ignition, but especially with points, a coil (and the points too) can get super hot if the key is on just when the points are at just the right point in their cycle.

So keep the key ON time to a minimum when you can. Not that it'll kill a coil immediately of course, but why take the chance with an older coil or one that's not quite as robust as others.
Good luck with your timing.

Paul

 

[71massbronco]

Thanks Paul, appreciate it.

 

[blubuckaroo]

Like Paul said. I've replaced the coil three times. Each of my sons has tried to park and listen to the radio with the switch in the on position. When the coil fails like that, is's an easy diagnosis. The bellows at the base of the coil will push out from the heat expanded oil.

 

[SHX669]

My son did the same thing with his Bronco ; I reminded him that was what the ACC part of the ignition switch was for ; he reminded me that the previous owner had wired CD player to "run/on" side of switch and i forgot to help him rewire it. - touche - or Mexican stand off /
SHx

 

[Broncobowsher]

I have also had a set of point burn out from the key in the run position and the engine off.

I have also heard of one of the electronic ignitions that will also burn out if left in run.

 

[admin]

I think that's a lesson most classic Ford owners learn at one point or another. When I was 16 I learned it on my 68 Mustang. I left the key in the ACC position while I tried to track down some brake light issue or something.

And I didn't have the interweb back then to quickly diagnose the problem. Luckily my local parts store had employees who actually knew about cars!

 

[Spartan]

Not just fords, any classic car, truck, tractors etc that run points are going to burn the contacts on the points if the keys left in the "on" position.
Also, I had a 67 Plymouth GTX and mopars were notorious to expanding oil in the coil cutting off spark from the heat since they're mounted on the intake, years ago I got in the habit of removing the coil from the intake and mounting it as far from heat sources as possible.

 

[DonH]

If you are not using the resistance wire from the ignition switch to the coil it will get hot very quickly if the coil is not designed for 12 volts.