Need help with gas furnace problem

Gas furnace: Ko-Z-Aire, Model 90 GV, Rated Input/Output per hour: 90,000/72,000 BTU
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 and white).
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 avail.
So:
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 gas valve?
Thanks, folks, for any help!
David
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This is Turtle.
I can't just get a good picture of what type system you have. From what you say here i'm taking it you have Mill volt type system with a Pilot lite Millvolt generator. If this system is another type such as central air gas furnace with ductwork and blower to circulate air through out your house. I'm all wrong here. I'm will speak you as have a Gravity type system with maybe a small electric blower in it to circulate some air in the room it is in.
Other names of what I'm talking about Gravity heating systems Wall furnaces Wall mount inferay heaters Floor mount gravity heating system.
The pilotstat as you speak of is the power supply to open the gas valve and have from 250 millvolt to 750 millvolts to control with. this pilotstat you say will have a thermocouple attached to it and leads to the flame of the pilot lite and directly infront of flame of pilot lite. When a person has intermitte problem with the system working and and stops for no reason. It usely is 1 of two things.
1) The Millvolt generator is defective and needs to be replaces but you need the exact millvolt rating of the generator. 2) the pilot lite is just a little dirty and does not let enough flame hit the generator to generate enough millvolts to open the gas valve. Clean the polit jet out and get flame back on the millvolt thermocouple generator. It will look the same as a hot water tank pilot lite thermocouple but usely it will be fatter that a 24 volt thermocouple used on hot water tanks.
What i think you have a dirty pilot lite jet and not getting enough of flame to the thermocouple.
TURTLE
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