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daddyjohn's Avatar

Join Date: Aug 2007
Posts: 2,021

10-29-07, 12:58 PM   #5 (permalink)  
Great photos! Any chance you can post the wiring diagram?

That system uses a mercury flame sensing switch that has cold and hot positions. Basically, on a call for heat, the sparker starts and the pilot burner gets gas. The pilot flame warms up the mercury sensng switch which changes position from cold to hot and allows gas to go to the main burner. There is an internal pressure switch inside that gas valve which keeps the pilot on once the flame sensing switch goes to it's hot position. If the pressure switch goes South, you have to replace the gas valve. Some models also had a resistor in the flame sensing circuit. I'm not sure if those parts are still available. I'm thinking there is an upgrade to a more modern ignition system, but not 100% sure. it's been a while since i have serviced one of these systems. I sure would like to see that schematic if possible. Concerning the sparker ticking when the t-stat is not calling for heat. Did you install a digital thermostat? Many of them use triac switches which have a small current flow thru them even when not activated.

Last edited by daddyjohn; 10-29-07 at 01:06 PM. Reason: add txt