mvallyman
I wasn't aware it was on a separate system.
My impression was that it was hooked to the same battery.
Here is a little reading on setting up relays and switches.
http://www.kpsec.freeuk.com/components/relay.htm
Unless somewhere in your system you have a shared ground, I would then say your problem is at the contacts
of the switch.
When your contacts disconnect, they are causing an arc which in turn is being picked
up by your receiver.
In my shop when I turn on the fluorescents, the servos in my planes will twitch.
This is not due to the lights, but the switch in the wall.
I would first try the diode across hookup points on the switch. (diodes are cheap)
I would imagine you just have the positive wire going through the micro switch.
Put the banded end (cathode) towards the battery and the other end (anode) towards the glowplug.
Another option would be to acquire a better micro switch. As stated earlier, make sure it is large enough to handle
the current of the glow plug.
Keep us posted,
Don J