Gas furnace: Ko-Z-Aire, Model 90 GV, Rated Input/Output per hour:
PilotStat: Honeywell, Type C418A1
Location: Baltimore, MD
Here is the problem: The furnace stopped turning on recently even when
we set the thermostat to very high. The thermostat has two wires (red
Jumpered the two wires at the thermostat, still didn't fire up.
The furnace has a magnetic gas valve. Jumpered the two wires at the
valve (disconnected the two wires at the thermostat since the manual
says not to do it because it is bad for the thermostat, why?), the
furnace DID fire up!
The two wires from thermostat: One goes directly to gas valve, one
through the PilotStat, so it seems the PilotStat is the problem. Only
two things are connected to the PilotStat: the electric wires (one
goes to thermostat wire, the other to gas valve) and a thermocouple.
Replaced the thermocouple with a brand new one from Home Depot to no
1. Did I diagnose the problem correctly, that it is the PilotStat that
is the problem?
2. How do I find a replacement for this PilotStat? Can I just get a
generic PilotStat instead of the original part? Where from and how do
I find the correct match? I have no idea how old it is. The house was
built around 1955.
3. Just a side question, what is the PilotStat doing anyway? Right
now, the pilot burner keeps burning (although now we have turned the
gas input off so it is completely dead). Is this PilotStat supposed to
control the gas input to the pilot burner? If the burner is always on,
and the electric on-off switch is controlled by the thermostat, why do
we need a PilotStat? Is it OK to just bypass the PilotStat altogether,
and connect the two wires from the thermostat directly to the magnetic
Thanks, folks, for any help!