Hello, I have had 20 years of no troubles with the no-frills Flowmatic. DHW diaphram and a fan with noisy bearings are the only faults until now.
The burner will not fire up on a call for HW or CH. Both valve switches are actuating and electrically sound. The fan spins up as it should when a call for water or heating is made. The pressure switch for the fan is operating when the fan speeds up. 240v AC is switched to the gas valve solenoid for either service. I am not au fait with what voltages should be seen at the modulator coil but there is a change and that seems to be about 4VDC on what should be the burner start. Pilot is a clean solid flame. There is only one item I cannot test and do not know how it affects the gas valve. That item appears to be a bulb stat with two possibly capillaries (?) running to the gas valve. "High limit stat" (interrupter). It is in a pocket below the safety stat (which shows continuity) and is connected to the rear of the gas valve and also the top right directly under the pilot thermocouple.
Any input to save throwing money in the wrong place would be appreciated.
The burner will not fire up on a call for HW or CH. Both valve switches are actuating and electrically sound. The fan spins up as it should when a call for water or heating is made. The pressure switch for the fan is operating when the fan speeds up. 240v AC is switched to the gas valve solenoid for either service. I am not au fait with what voltages should be seen at the modulator coil but there is a change and that seems to be about 4VDC on what should be the burner start. Pilot is a clean solid flame. There is only one item I cannot test and do not know how it affects the gas valve. That item appears to be a bulb stat with two possibly capillaries (?) running to the gas valve. "High limit stat" (interrupter). It is in a pocket below the safety stat (which shows continuity) and is connected to the rear of the gas valve and also the top right directly under the pilot thermocouple.
Any input to save throwing money in the wrong place would be appreciated.