I installed an aftermarket trailer brake on my hunting rig. I mounted it a little too high for the double-sided key ring I carry and when the keys are in the ignition and brush against the controller, I get sparks. The simple solution is, a separate my keychain; problem solved, BUT.......

I assume either the ignition or trailer brake isn't properly grounded? It was a simple installation and nothing was bubba'd. The cord from the brake controller plugged into the factory wire harness.

Thoughts?

If you're getting sparks, it's not the ground. You have a hot wire in contact with the controller that needs to be fixed or you have a defective controller. Look behind the screws on the mounting bracket to start with. You might have run a screw into a wire back there.
Use a test light or multimeter to check for a hot controller housing. Try it with your foot both on and off the brake pedal.

As a starting point, find out if there's current from the controller casing to a ground with the key turned off and on. If there is, either way, remove the mounting screws 1 at a time and recheck. If you get all the screws out and still have a short to the case, look at your wire connections to see if there's a short there. If not, you might have a bad controller.

Shouldn't have a hot controller housing. I think it's plastic, BUT I will verify and check as you've instructed.

Thanks!

If it's sparking, your keys are hitting something metal and hot. Maybe the mounting bracket? That's why I think you might have run a screw into a hot wire behind it.

Defective controller.

I pulled the controller out of the plastic mounting bracket to remove the screws as instructed above. Long story short; I brushed the face of the controller against a bolt which anchors the drivers seat. The sparks flew.

Thanks Rock Chuck.

I'm glad you found it before it fried something expensive. It doesn't take much to cook some of the electronics in newer cars.

More good news: I contacted Hayes, told them what the problem is and they said mail it to us and we'll mail you a new one. Great customer service from an American company and what is touted to be an American-made brake controller (Hayes G2 Brake Boss).

Thanks again.