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co5j 01-11-2009 09:21 AM

RUUD gas furnace wont stay running
hey guys, i'll try and give as much info as possible, feel free to ask for more. we have a RUDD LP gas furnace, URMA-AD42JK10E, build date is 2002. about 2 winters ago the heat exchanger was bad, part (not labor) still under warranty. worked fine since. Friday we awoke to frost, on our noses. i went out friday afternoon and opened it up. the LED indicated rollout switch, which i reset, unit came on but only ran through 1 or 2 cycles then wouldnt come back on. the rollout wasnt tripped this time, i powered off and back on, watched the burners, there are 5. sometimes only the first burner would ignite and since the flame sensor wasnt getting a flame, it would shut the first burner off and after about 30 seconds try again, at which time all 5 burners would light. this worked for a while then it quit again. i reset power and watched again, this time 3 burners lit, went off for 30 seconds and re-lit all 5 and actually ran all Friday night but stopped early saturday morning. i shut everything down, took the burners, the igniter and flame sensor out and cleaned everything real good with wire brushes, bottle brush etc. put it all back together, started perfect first try so i buttoned everything back up and hoped for the best. it wasnt terribly cold yesterday or last night, i did hear it running overnight some, but this morning it isnt running. it's raining here so i havent opened it back up but it's going to get cold this week . any ideas i can try before i have to call someone in?

SKIP4661 01-11-2009 09:35 AM

How much propane do you have in your tank. Could be a fuel issue. Maybe a problematic regulator.

yuri 01-11-2009 09:40 AM

Carefully check the vent screen on both regulators (tank and house) for blockage. They can get frozen up and cause the regulator to malfunction. This is a VERY serious situation as it can overpressurize the line and furnace and cause an explosion. Build a rain cover over them for safety.

co5j 01-11-2009 09:41 AM

tank is at about 70%, shouldnt be an issue. also checked filters, they're not an issue either.

yuri 01-11-2009 09:43 AM

Blocked vent can cause low pressure also.

co5j 01-11-2009 09:58 AM

i'll go take a look when the rain moves off this afternoon. as for freezing up of screens, is that as in ice? cause i know up in winnipeg you're probably fed up with the cold, i'm in coastal NC so "cold" to us is 30-40, not much ice yet. sorry. but it is expected to get into the teens and 20's overnight this week. if you can think of anything else i need to look at when i open it back up i'll post what i find later. thanks for the help.

yuri 01-11-2009 10:02 AM

They can ice up or get blocked with debris. I grew up here so I am used to it. 10 months of hockey 2 months of bad sledding.

heaterbeater 01-11-2009 10:05 AM


co5j 01-11-2009 10:10 AM

not sure what overfired means. sorry.

heaterbeater 01-11-2009 11:14 AM

burner manifold pressure too high,possibly from day one. Have a pro check that spec. pressure.

co5j 01-11-2009 02:36 PM

from day one? it's been in operation for 5-6 years now with no problems, not sure i understand. i just went out and opened it backup, the rollout switch was open BUT the indicator light wasnt showing any faults, glowing steady.

co5j 01-12-2009 07:02 PM

rollout switch only holds about 5 minutes as of tonight. as stated before, the heat exchanger was replaced under warranty less than 2 years ago. in looking at the 5 burners with it dark outside, they are the burners that are connected to each other at the side flanges for cross-lighting. they look like little airplane wings, supposedly a newer improved design. but after igniting, in adition to the large flame shooting out of the center of each burner into the exchanger, there is a solid flame all the way across the front flange of all burners, closest to the exchanger, that looks to be possibly heating up the frame that the rollout switch is mounted to causing it to open. is this normal? i'm assuming it's not and if not, is it likely the burners themselves bad or could there be another cause?

Daltex 01-12-2009 07:16 PM

Did you check the flue for blockage?

co5j 01-12-2009 07:22 PM

by flue, are we talking the vent pipe on the outside of the unit that just vents from the blower up into the air? this entire unit is outside, vents right to the air. there is plenty of exhaust coming out but no, i havent actually taken the pipe off the side where the blower feeds into it.

yuri 01-12-2009 07:51 PM

I am wondering if that unit has chronic problems with the heat exchanger cracking? First one only lasted 4 yrs? It may also be partially plugged as propane if not setup properly can sootup the heat exchanger. Usually with a cracked heat exchanger it can take 5 minutes of running B4 the crack opens wide enough for the fan/blower pressure to get thru and force the flames out and trip the rollout switch. You may have a bad heat exchanger again/and or/one that is failing because of other reasons. Overfiring/overheating due to poor airflow etc. They usually don't fail that soon for no reason.

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