Plumbing Questions? Ask a Plumbing Expert.
How old is the heater? Have you ever had it descaled? This unit should be descaled every year or two. It is also possible that there is a problem with the wire to the controller. You can easily open the panel and check the wire harness and / or connection. This could be an issue with a bad connection. I would recommend a descale with cleaning the intake and exhaust vents. Also, have the plumber check the burner area for debris and clean the ignitor. Good Luck!