Old coleman propane furnace blues..

spaz

On call for heat, my Coleman down flow DGAA070BDTA operates correctly until the main burner ignites, but then shuts down the valve after a few seconds.. IMO the flame sensor is not proving flame, so furnace performed a safety shut down but tried to light a few more times.. What's the chances the flame sensor S1-02535354000 only needs cleaning, and if the entire assembly falls apart in my hands as I remove it? The furnace actually did fire for a extended period when first tested..

Its windy today so Ill warm the house cooking, and try the furnace later, which might suggest a venting problem. How important is it to have combustion air drawn from outside through colemans proprietary concentric vent? I do have some experience and feel Im on the right track, but I just have this feeling because of all the events leading to this.. Like the river running through my ductwork etc etc.

And a unrelated question.. Retired now, Ive spent most of my career around the HVAC industry, universal certification and used to have connections when buying and installing my own. Regretfully Ive worked for the state for two decades and lost all the connections.. How would you go about buying a new coleman furnace if in my situation, because I know of four aging family systems that could use a change out, and that was my specialty decades ago. But things have changed.🙄

Thanks!

mattmia2

Does it have an intermittent pilot or does it light the main burner directly? Is it hsi or spark ignition?

spaz

https://forum.heatinghelp.com/discussion/comment/1814159#Comment_1814159

Hot surface ignition..

I also found the silicone grommet that air seals the wires leading to the burner assembly was missing. Just got back from town with a grommet from a bad burner assembly from my other houses water heater.. Will try to fit it because there was one heck of a draft coming through it this afternoon.

mattmia2

Is it intermittent pilot or does it ignite the main burner directly?

spaz

https://forum.heatinghelp.com/discussion/comment/1814196#Comment_1814196

It has a hot surface ignition which is operating correctly. I replaced the silicone grommet where the wires enter the chamber and the furnace stayed lit… But slowly the flame became very blue, wandered and blew out and then re-lit. Looked like no combustion air but it's running, which would mean a weak gas valve not staying open?

mattmia2

I'd check the gas pressure, probably something with the gas supply if the flame slowly dies then goes out.

I ask if it is intermittent pilot or if it is directly lit by the hsi to determine where in the cycle it needs to prove flame. It uses flame rectification to prove the flame so you have to make sure the wire to the flame sensor isn't chaffed or burned and shorted somewhere but the burner also needs to have a good bonding all the way back to the ground of the ignition control so a small current can flow through the flame.

spaz

https://forum.heatinghelp.com/discussion/comment/1814248#Comment_1814248

I dont have a lp gas gauge, but four burning stove top flames in the kitchen didn't change as the furnace started and ran, and actually continued to run and shut off by the thermostat this last time. No problems with the gas water heater either, but I dont trust the furnace to make it the one last winter I need it to like its running.

Im thinking the gas valve is either open or slam shut, meaning I still have a issue with incomplete combustion. Because the flame is more orange when it lites, and then blue and almost intermittent.

I'll work on getting a manometer.

Thanks again..

EBEBRATT-Ed

Could be a bad Heat exchanger flame lights ok then goes crazy when the indoor blower starts

SuperTech

Is this a mobile home furnace? From what you described I would check combustion air supply and gas pressure. With LP you could have a regulator that is only for the furnace that is failing. That would explain why the other appliances aren't affected. If it is a mobile home furnace then typically the hot surface igniter is also the flame sensor. Never liked those setups.

spaz

https://forum.heatinghelp.com/discussion/comment/1814320#Comment_1814320

Yes, it's a mobile home furnace and I have a manometer on the way.

Where would that regulator for the furnace be located?

The burner assembly looked pretty good and I cleaned the flame sensor and the furnace operated as designed. My flame sensor is separate from the hot surface igniter, but the flame doesn't look right to me so I'll try to inspect the inside exhaust pipe to see it it rusted through and is leaking exhaust into the combustion air.

mattmia2

I'd check the voltage at the gas valve too, it could be turning on and off because it is intermittently proving flame. if the voltage drops the control is probably losing the proof of flame and shutting the valve off