Control board sees power supply frequency not in range of 59 to 61 Hz.
1. Is power supply between 59 and 61 Hz?
Yes: -> 2
No: Provide frequency stabilized power supply rated at 60 hz +/- 2%
2. Is power supply circuit breaker loose or faulty?
Yes: Replace circuit breaker.
No: -> 3
3. Is field wiring loose of faulty?
Yes: Correct wiring
No: Replace control module.