Stumper Atwood 2540 problem

[coastRVer]

I am having a really annoying problem with my older atwood 2540 2 stage furnace (8900-III). It is an older furnace so parts have become limited.

Every time the furnace shuts down, we get a propane odour. Sometimes weak, sometimes very strong. It also has melted 2 combustion wheels. There are also signs of incomplete combustion (lots of soot, etc) I have blown and sucked out the combustion chamber to clear any obstructions. Burner head also looks fine.

I can hear that propane valves are delayed in closing some of the time... I know it is supposed shut off the propane, and then the blower keep running to evacuate the exhaust, but it seems like the valves are being told to stay open until the fan shuts off and then they close afterwards - I have confirmed this by putting a multimeter on the solenoid valve connection and there is power to it until after the fan shuts off and then the valves lose power and you can hear them click shut.... so it doesn't seem like a mechanical jamming/failure in the solenoid valves itself. It seems to me like they should close immediately and then the fan should run for another 30 seconds (or whatever the time delay is) When you turn it off at the thermostat the fan runs for a while still so the fan is still on a time delay of some sort.

This leads me to conclude that the valves are being told to stay open by the logic board(s) until after the fan shuts off, which seems like the incorrect sequence of events? The odd time I can hear a poof after it shuts down as well... This make me think that it has propane in the combustion chamber and when the fan shuts down it is depleted of oxygen to the point that the flame is nearly extinguished and the odd time there is a small explosion due to the excess propane stuck in there.... which is causing the soot and melting the combustion wheel... also the propane smell.

I have tried replacing the ignition board... It didn't make any difference. I know it seems like a strange way for a logic board to fail but I'm not sure what else to conclude if it is being told to stay open. There are two boards in my unit, the "dual control" board and the "ignition board"... do you think it's worth changing the dual control board? I started with the ignition board because it is the one that the wires run to the propane valves.... but the control boards are tied together with a couple wires so perhaps this logic portion comes from the other board, and the ignition board is simply a relay for power to go to the solenoid valves.

The propane smell goes away completely after it has shut down for a while and airs out.

Anyone ever see or hear of this happening before?
any ideas?

thanks,

[Reverse_snowbird]

Originally Posted by coastRVer

when the fan shuts down it is depleted of oxygen to the point that the flame is nearly extinguished and the odd time there is a small explosion due to the excess propane stuck in there.... which is causing the soot and melting the combustion wheel... also the propane smell.

A small explosion! Unfortunately, I can't help you solve the problem, but you need to find someone who can or replace that furnace.

[SeaDog]

Welcome to the forum its a great place to get your questions answered. What rig do you have Make, Model, year. Sounds to me like a faulty gas valve. JMHO

[boondocking]

Originally Posted by SeaDog

Welcome to the forum its a great place to get your questions answered. What rig do you have Make, Model, year. Sounds to me like a faulty gas valve. JMHO

Atwood 2540

[bikendan]

Originally Posted by boondocking

Atwood 2540

I think he was asking for information on the OP's RV, not the furnace.

[boondocking]

Originally Posted by bikendan

I think he was asking for information on the OP's RV, not the furnace.

Are different models of the Atwood 2540 put into different models of Trailers?

[5picker]

Originally Posted by boondocking

Are different models of the Atwood 2540 put into different models of Trailers?

I'm not jumping into the middle of this particular query but... some folks believe so.

I had a fellow a few weeks ago tell me on another R/V forum that the Suburban SW10DEL water heater in his Jayco Pinnacle Luxury 5th wheel was NOT the same model they put in less expensive makes/models.

Back to your regularly scheduled programming...

[SeaDog]

The reason for asking was to so that someone on the forum with the same rig who may not know the furnace model might be able to provide an answer. I fully understand a model of furnace regardless of what it is installed in is the same furnace I didn't just fall of the turnip truck on the way to town.

[Mr. Dan]

Originally Posted by SeaDog

The reason for asking was to so that someone on the forum with the same rig who may not know the furnace model might be able to provide an answer. I fully understand a model of furnace regardless of what it is installed in is the same furnace I didn't just fall of the turnip truck on the way to town.

Speaking of "turnip truck", this one was mine!

[boondocking]

LOL

[SeaDog]

its an old time saying, good pic LOL

[boondocking]

Originally Posted by coastRVer

I have tried replacing the ignition board... It didn't make any difference. I know it seems like a strange way for a logic board to fail but I'm not sure what else to conclude if it is being told to stay open. There are two boards in my unit, the "dual control" board and the "ignition board"... do you think it's worth changing the dual control board? I started with the ignition board because it is the one that the wires run to the propane valves.... but the control boards are tied together with a couple wires so perhaps this logic portion comes from the other board, and the ignition board is simply a relay for power to go to the solenoid valves.

The propane smell goes away completely after it has shut down for a while and airs out.



thanks,

Is there any way to interrupt the connection between the two boards while this problem is happening. To see if the gas valve powers down.

[campers302]

Originally Posted by coastRVer

I am having a really annoying problem with my older atwood 2540 2 stage furnace (8900-III). It is an older furnace so parts have become limited.

Every time the furnace shuts down, we get a propane odour. Sometimes weak, sometimes very strong. It also has melted 2 combustion wheels. There are also signs of incomplete combustion (lots of soot, etc) I have blown and sucked out the combustion chamber to clear any obstructions. Burner head also looks fine.

I can hear that propane valves are delayed in closing some of the time... I know it is supposed shut off the propane, and then the blower keep running to evacuate the exhaust, but it seems like the valves are being told to stay open until the fan shuts off and then they close afterwards - I have confirmed this by putting a multimeter on the solenoid valve connection and there is power to it until after the fan shuts off and then the valves lose power and you can hear them click shut.... so it doesn't seem like a mechanical jamming/failure in the solenoid valves itself. It seems to me like they should close immediately and then the fan should run for another 30 seconds (or whatever the time delay is) When you turn it off at the thermostat the fan runs for a while still so the fan is still on a time delay of some sort.

This leads me to conclude that the valves are being told to stay open by the logic board(s) until after the fan shuts off, which seems like the incorrect sequence of events? The odd time I can hear a poof after it shuts down as well... This make me think that it has propane in the combustion chamber and when the fan shuts down it is depleted of oxygen to the point that the flame is nearly extinguished and the odd time there is a small explosion due to the excess propane stuck in there.... which is causing the soot and melting the combustion wheel... also the propane smell.

I have tried replacing the ignition board... It didn't make any difference. I know it seems like a strange way for a logic board to fail but I'm not sure what else to conclude if it is being told to stay open. There are two boards in my unit, the "dual control" board and the "ignition board"... do you think it's worth changing the dual control board? I started with the ignition board because it is the one that the wires run to the propane valves.... but the control boards are tied together with a couple wires so perhaps this logic portion comes from the other board, and the ignition board is simply a relay for power to go to the solenoid valves.

The propane smell goes away completely after it has shut down for a while and airs out.

Anyone ever see or hear of this happening before?
any ideas?

thanks,

You are talking about GAS AND FIRE!
GET A PROFESSIONAL BEFORE SOMETHING BAD HAPPENS!

[TheWolfPaq82]

Question: How do the burners go out if the valves are not closing right away ??