Quoted:
Quoted: Go up to the unit, Take off the main burner control panel. Have some one select "heat" and set the T-Stat to 100. watch the igniter...does it glow? or if its a spark ignition does it spark?
My bet is that it is NOT the T-stat, but lets take it 1 step at a time.
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Haven't got anyone to help with this right now but I hear what you're saying as I've replaced thermocouples on water heaters a few times. The owner's manual states
3. As the thermostat calls for heat, the system cycles as follows:
1. Combustion blower is energized 2. The Pressure switch is closed 3. The gas valve opens and the ignitor lights the burner
The IGN Diagnostic LED indicator manual mentions
System Lockout Pressure Switch Problem High Limit (TC)) Open Flame sensed with Gas Off Flame Rollout Switch (FL) Open
I can see how it could be a few things, ignitor most likely.
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Ok you do need to read that code flash. System lock out means just that...something was wrong so the system locked itself.
Pressure switch, is the small fan that pressurizes the vent. if the vent doesnt pressuize properly the system will lock out. the pressure switch is the round sensor with two tubes going into it. that is what tells the fau the vent is under pressure.
High limit is the internal senor that checks to make sure the heat exchanger isnt over heating.
flame sensor is sorta tricky, it will will trip if either the flame is sensed, (sensor shorted) when no flamne is there, or will trip if the gas valve is open but the sensor doesnt heat up.
Roll out sensor is a small disk like sensor in several places, if any of thoses get hot, it will lock out the system...think of them as small fire detectors.
My bet is on either a bad ignitor...a bad vent switch...or the flame switch doesnt sense the flame or the flame isnt carring over to the sensor.....but you really need to watch the system cycle.
1)call for heat....click at Tstat, heat light on at tstat.
2)click at gas valve...
3)3 seconds after GV click, small vent fan turns on.
4)2 seconds after fan turns on, pressure switch tells GV vent is ok.
5)Ignitor starts up..2 seconds after that gas flows.
6)Gas is lit, sensor tells GV flame is present.
7)after several seconds heat exchanger gets hot, Blower fan switch says go, fan turns on to circ hot air into house.
at any of these points the system will shut down if its a no go. The "clicks" are basicly relays closing telling you the signal was sent and received.