Monessen Stove Replacement Parts & Accessories

The switch likely needs to be replaced unless the millivoltage isn't adequate enough to consistently open the flow of gas once the circuit is closed. You could determine if the switch is the culprit by removing the switch wiring from the two outer terminals on the gas valve labeled TPTH and TH and then using a jumper wire across these two same terminals to see if the burner flame ignites and extinguishes without issue. If so, the switch requires replacement. If not, a service call is in order to see if routine maintenance and cleaning of the thermopile will increase the millivoltage to adequate levels.