Coleman Presidential furnace 4324-729 disassembly

Well, after some distractions, and a knuckle scrape or two, the unit was removed and the thermocouple replaced.

Much to my dismay, still, the pilot light will not stay lit.
The flame is strong, with proper color, when the button is held down.

Even after minutes with the button held, no standing pilot when released.

My next step will be to remove the flame end of the thermocouple, and set over an alternate flame, such as a candle. This may remove the possible issue of improper pilot positioning, and can be done without fully removing the unit again.

After that, I'm thinking gas control valve replacement (with proper LP orifice).

I know that there are two sensors related to preventing an over run/heat condition on this unit. A disc-like sensor mounted along the heat exchanger up & behind the valve, and a rectangular one mounted directly on the front of the unit just left is the pilot burner connection. There is also a fan 'flag' sensor.

It is my understanding that these come into play during operation, and are not a factor until the control valve is moved into the 'On' position. Regardless of their condition/fault, the pilot should still stand in the 'Pilot' setting.

Am I correct in this assumption?
(in correlation to other units/types I have repaired)

Any further help would be appreciated.

Any recommended supplier of this valve?
(which of course, I did not, happen to record the brand/model of while disassembled)

Thanks again

I usually pull the exterior assembly first, but it might be easier to simply pull the whole assembly from the inside first- you can wiggle it back and forth to loosen the slip fit vent.

These were good units- the heat chamber is good and heavy- I have yet to see one rusted through., something I cannot say about Suburban or DuoTherm units.

I'll look again for that 'other' screw, but I think I have all of them removed.

Thanks for the information, it looks just like what I'm working with. (figure 1)

I'm wondering if the exhaust port of the heat exchanger isn't rusted onto the exhaust tube that extends to the exterior. I'm assuming it's simply flared to slip over the exhaust port of the heat exchanger. (I've even looked from the exterior vent to see if there was some phantom screw there because it feels that way)

I've soaked the inside of the exterior vent tube with penetrating oil in efforts to free it.
(I KNOW, I know... I'll be sure to be VERY careful when I get this thing to fire up, with a buddy, who's versed in extinguisher use.)

I'll be back at it tomorrow or Saturday; let you know how it goes...
Thanks again.

I threw this together- http://bryantrv.com/docs2/docs/coleman4300.pdf- it should help. I should have a real manual, but all of my Coleman manuals are for older models (!).