Have a 7 year old Minimax NT 200. Have a couple issues. First was no power on secondary side of transformer. replaced transformer. Second problem was ERR code on display. Replaced thermister. Now display shows water temp and other lights.

Last problem is the heater won't fire. Have a code E04. Replaced air pressure switch, and igniter. The igniter had an ohm reading of 11,125 ohms.

Blower runs, can hear a solenoid click, I assume this is the gas valve. I do not smell any gas

Any ideas?