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-   -   moncrief gas furnace ( 02-10-2007 09:02 PM

moncrief gas furnace
this furnace fails to light after three attempts. then after A reset of the board will usually ignite fine. saw a previous post about a possible flame sensor problem. any info about resistance specs or other information would be greatly appreciated. by the way this is supposed to be now a luxaire division. 02-11-2007 04:29 PM

More info on Moncrief
Let me try to give better info 1st this unit was built by Evcon Industries now owned by York who also has Luxaire and coleman and all of that is under johnson controls. Now what is important is that after reading alot of posts on this site it seems alot of these units work very similar. My natural gas furnace will see the thermostat demand, start the exhaust blower, and glow the ignitor. When the problem occurs the ignitor will try 3 times and go to one hour lockout-burner failed to light 3 tries. owners book says to check gas flow and pressure. Doubt I have tools for that. But flame seems even and blue when unit lights. Have had DVOM on gas valve and do not have 24 volts unless it does light. book also says check flame sensor. DVOM 1 lead to single wire of flame sensor other to case 92 V not burning 77 burning. Have never seen unit quit burning early once lit. seems to lean to board failure to me. once again any help much appreciated

rakes9720 02-12-2007 02:42 PM

Check wiring to gas valve. It sounds like a wire is loose preventing 24V therefore preventing flame.

Disconnect the flame sensor, and attach and attach an ammeter to the two separated termials. You should get current when there is flame. If you don't, clean the sensor.

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