You say the meter is not showing any current. What about the plug itself? It could glow even if the meter is stuck. If the plug is not glowing, hold your plug wires directly to the battery momentarily. If the plug glows, you know the battery, plug and leads are OK. If you hold the lead to the battery for more than a moment, you may burn out the plug, so be careful. If there's no glow, touch your plug and leads to a C or D battery. If that glows, then plug and leads are OK and the cell is the issue. If no glow, then either the plug or the lead is bad.
To troubleshoot the rheostat you will need a voltmeter. Of course, if you have a voltmeter, you can use it for all the checks described above also. The rheostat has three terminals. The center one goes to the moving wiper, and the other two go to opposite ends of the winding. One will be connected and the other will not. Set your voltmeter to read DC ohms. From one end of the winding to the other, you should read 1 to 2 ohms. If you read no continuity, the winding has an open spot, which is no good. If you connect one test lead to the wiper terminal and the other test lead to either end of the winding, you should see the resistance go up and down as you move the control lever side to side. If you don't see any connection at all, make sure the wiper is touching the windings, and the contacting surfaces are clean. If you are unable to get continuity, then something about the rheostat is bad.
OR, send it to me and I will troubleshoot and repair it for no labor charge, cost of parts and shipping only.
Bill Bischoff