1. Check voltage across the top center tap and either of the two top taps.
2. If there is power look for a bad connection between the power connection block and the transformer.
3. With the power to the kiln off, open the control box carefully and make sure that nothing is touching any of the exposed wires.
4. Turn the power back on.
5. Locate the transformer. Most have 3 wires on the bottom of them- the center wire is actually a jumper wire connecting the two center terminals, and three wires on the top of it- all wires are on one side of the transformer.
6. Use a digital multimeter to check transformer operation.
7. Set your digital multi-meter to AC volts, the next setting higher than 240 volts AC (on a lot of meters this is 600).
8. Check voltage across the top center tap and either of the two top taps.
9. With the meter you should be able to read 240 or 208 volts AC on the outer two wires at the bottom of the transformer. (These power wires come from the toggle switch and the power block). If there is 240 or 208 volts there everything is good up to the transformer.
10. Set the meter to read 24 volts AC and look for this on the outer two wires of the 3 wires at the top of the transformer. If there is no voltage there then the transformer itself is faulty and you need to replace the transformer.
11. If there is no power go further back on the line and measure the voltage. Keep going until you find voltage.
12. Look for the problem between the point with the voltage and the last point checked that had no voltage.
13. Replace transformer if you are not getting proper voltage.
14. If there is proper voltage there then the control is getting the correct incoming voltage and that the board itself is probably faulty. Replace the control.

CAUTION: This test should only be done by an experienced person familiar with electricity.

See this tutorial on how to use a multimeter.

See this video: