FAQ: Controller Display Shows NO or NO AC

Q: Why does my controller display show NO or NO AC?

A: The NO or NO AC display is a diagnostic message telling you that the controller has stopped receiving AC power. The controller is running on the power supplied by the back up battery.

Check the power source by plugging a lamp or radio into the wall outlet to verify there is power at the outlet. If your controller is not plugged into a wall outlet, the power source is hardwired. Controllers that are hardwired to the power source will need to be tested by a qualified electrician.

If you do not have power to the outlet, check all wall switches, timers, or power strips that may be connected to the outlet. Have an electrician check your GFI, circuit breaker, and electrical outlet if you do not have power to the outlet.

If you can verify that you have power to the outlet, disconnect the back up battery from the controller.

If the display goes blank after removing the battery, the transformer could be damaged and may need to be replaced. A transformer can be tested with a voltmeter. Normal voltage output is 24-26 Volts AC. Click on this link to see a list of replacement parts and to find a local distributor.

If the display stays live after removing the battery, the controller processor has received a voltage spike and will need to be reset. Select your controller model from the following list for reset instructions.

1. SRC
2. SRC Plus
3. EC
4. Pro-C
5. ICC
6. XC