Hi, I recently purchased an '06 FWC eagle. The heater had been disconnected for years because the owner used it in Mexico where someone stole the fridge so he capped off the gas line because he didn't need it anyway. Now that I'm using it in Colorado I need it to fire. I reconnected the propane, clenaned it and diagnosed a bad thermo after bypassing it. I put in a new Atwood thermostat and it only ran the fan for a few minutes and shut off. The error showed an air flow limit fault. I took one of the duct blanks on the top of the unit off and it fired right up and pushed heat until I turned it off. While this is a victory it also means that it blows hot air straight up into the cabinet where the fridge should be. I planned on using that for storage though. Any thoughts on how to remedy this?
Heater in '06 FWC eagle
- Thread starter Joel H
- Start date
CougarCouple
Senior Member
Hi Joel
First off hello and welcome to WtW, and congrats on the camper.
I believe the air flow safety is to prove the blower runs. You don't want fire w/o blower. That said I would look is there an obstruction somewhere. If not could the switch be weak(there are different types so I don't know what yours looks like). Is the blower operating properly, look to see if there are oil ports(use proper oil, do not over oil)
As you stated has not seen much use might just need to run a little. Try calling Atwood and speak to them ( I have found suburban does not want to help John Q. Public)
Look on their web site see if you can find owner operation instructions and installation manuals.
Have you looked at flame and checked color, yellow bad. Should be blue. Some manufacturers have a small viewing window, if combustion chamber is sealed.
Do search on this forum there might be info on same problem others had.
Russ
First off hello and welcome to WtW, and congrats on the camper.
I believe the air flow safety is to prove the blower runs. You don't want fire w/o blower. That said I would look is there an obstruction somewhere. If not could the switch be weak(there are different types so I don't know what yours looks like). Is the blower operating properly, look to see if there are oil ports(use proper oil, do not over oil)
As you stated has not seen much use might just need to run a little. Try calling Atwood and speak to them ( I have found suburban does not want to help John Q. Public)
Look on their web site see if you can find owner operation instructions and installation manuals.
Have you looked at flame and checked color, yellow bad. Should be blue. Some manufacturers have a small viewing window, if combustion chamber is sealed.
Do search on this forum there might be info on same problem others had.
Russ
Old Crow
Searching....
Hi, Joel H...
What happens when you put the duct-blank back in place and try to start the furnace? Does the air-flow/limit indication come back?
And what furnace model is it?
What happens when you put the duct-blank back in place and try to start the furnace? Does the air-flow/limit indication come back?
And what furnace model is it?
Yukon
Senior Member
Hi,
I had a similar problem. I found out a couple of things. If you put things in front of the furnace vents (like boots) it might impact flow and cause an issue. I also found that turning the outflow vent upside down (facing towards the flow) made a difference. What was happening is that air is sucked in from one of the vents and then blows out the other. If you suck too much hot air into the intake vent, it gets overheated and shuts off.
I don't know if this is your problem, nor do I claim to be an expert. If you do a search on my name on this site you will see that I had a LOT of problems with my heater. I bought a new one and things are going pretty well now. Chris
I had a similar problem. I found out a couple of things. If you put things in front of the furnace vents (like boots) it might impact flow and cause an issue. I also found that turning the outflow vent upside down (facing towards the flow) made a difference. What was happening is that air is sucked in from one of the vents and then blows out the other. If you suck too much hot air into the intake vent, it gets overheated and shuts off.
I don't know if this is your problem, nor do I claim to be an expert. If you do a search on my name on this site you will see that I had a LOT of problems with my heater. I bought a new one and things are going pretty well now. Chris
So here's where I'm at- I came home from work eager to answer these questions. I turned on the lp, flipped on the heater and nothing happened. Not even the fan turning on. So I bypassed the new thermostat by touching the two wires together and it fired right up. Then I put the duct blank back on and it shut off about 10 minutes later. I took the blank off and refired it the same way and it's been pushing heat for hours with no problem. Is the new thermostat bad? Seems like too much of a coincidence. The model is the Atwood 8516- ivdclp
CougarCouple
Senior Member
Hi Joel
If the stat is digital, did you get into the programming mode and set it up for your application.
Russ
If the stat is digital, did you get into the programming mode and set it up for your application.
Russ
Old Crow
Searching....
The failure-to-start of the fan seems very odd given the new thermostat but if you have a multimeter, it's easy enough to test its basic functionality. Set the meter to ohms, verify that touching the probes together gets a non-zero reading, then hold the probes to the wire-attachment screws while you operate the slider. If you get a non-zero reading when the contacts close, it's working. If the meter stays at zero when you operate the slider, check that those little contacts on the Off switch are closed. (Note-- there's a more detailed thermostat trouble-shooting guide on page 29 of the service manual below)
I've been looking through the service manual (the 2004 Atwood Furnace Service Manual) hoping to get a clue as to what would shut off the running furnace when you put that duct blank back in place. I'm not finding much. The manual's pretty good at providing a sequence of operations and describing the functions of the components. When it speaks of air flow, though, it more or less just says it's important to not have any obstructions in the vent-pipe, combustion chamber, heat exchanger area, duct-work, or return. I went out to look at my furnace (also an 8516-IV) and pulled the vent-pipe and removed the grille so I could look into the heat exchanger but there's not much opportunity to see.
I can't imagine what is shutting down the furnace when you put that duct-blank back in place. If a lack of air flow is causing the furnace to overheat, that could trip the high-temp limit switch but we still don't know why there's insufficient air flow.
Best use of your time may be call Atwood Tech Support for the most likely places to look for the problem. Before doing that you might test the thermostat so you have confidence in it, remove the vent-cap and look for evidence of mud-dauber constriction in the pipe, and get a look as best you can into the heat-exchanger area for evidence of some air-flow obstruction.
I've been looking through the service manual (the 2004 Atwood Furnace Service Manual) hoping to get a clue as to what would shut off the running furnace when you put that duct blank back in place. I'm not finding much. The manual's pretty good at providing a sequence of operations and describing the functions of the components. When it speaks of air flow, though, it more or less just says it's important to not have any obstructions in the vent-pipe, combustion chamber, heat exchanger area, duct-work, or return. I went out to look at my furnace (also an 8516-IV) and pulled the vent-pipe and removed the grille so I could look into the heat exchanger but there's not much opportunity to see.
I can't imagine what is shutting down the furnace when you put that duct-blank back in place. If a lack of air flow is causing the furnace to overheat, that could trip the high-temp limit switch but we still don't know why there's insufficient air flow.
Best use of your time may be call Atwood Tech Support for the most likely places to look for the problem. Before doing that you might test the thermostat so you have confidence in it, remove the vent-cap and look for evidence of mud-dauber constriction in the pipe, and get a look as best you can into the heat-exchanger area for evidence of some air-flow obstruction.
CougarCouple
Senior Member
Hi Joel
Intermittent problems are often the most difficult. I would suggest to keep notes. Jumping all over the place is bad néed to be systematic.
I did not see any one mention connections. Oxidation can cause problems and connections need to be tight. Some of the signals are very low voltageFind a sequence of operations for your unit mayb oldcrow has that and can post. As you go thru sequence of operations as they are proven then the heater moves on to the next. Sometimes the heater will light then fail in the middle of the sequence, the heater may or may not start back at square one. Also check the supplied voltage as this will often cause Circut boards to stumble when the voltage gets out of design specs. i.e. Blower is on but the drain is enough to drop out of CB needed applied voltage. Unit will stop there and won't move to next step.
The blocking and un blocking of this opening troubles me. As you state it operates when open but is problematic when closed Look to see did previous owner do something else which is causing the problem.
The thermostat should have a heat anticipating circuit this shuts heater off just before reaching set point. Remove cover look at for a bear coiled wire there should be a metal wiper, note position then move this blade up-down or back-forth to tru clean a little. A pencil eraser is good for cleaning thermostat contacts.
Russ
Intermittent problems are often the most difficult. I would suggest to keep notes. Jumping all over the place is bad néed to be systematic.
I did not see any one mention connections. Oxidation can cause problems and connections need to be tight. Some of the signals are very low voltageFind a sequence of operations for your unit mayb oldcrow has that and can post. As you go thru sequence of operations as they are proven then the heater moves on to the next. Sometimes the heater will light then fail in the middle of the sequence, the heater may or may not start back at square one. Also check the supplied voltage as this will often cause Circut boards to stumble when the voltage gets out of design specs. i.e. Blower is on but the drain is enough to drop out of CB needed applied voltage. Unit will stop there and won't move to next step.
The blocking and un blocking of this opening troubles me. As you state it operates when open but is problematic when closed Look to see did previous owner do something else which is causing the problem.
The thermostat should have a heat anticipating circuit this shuts heater off just before reaching set point. Remove cover look at for a bear coiled wire there should be a metal wiper, note position then move this blade up-down or back-forth to tru clean a little. A pencil eraser is good for cleaning thermostat contacts.
Russ
Old Crow
Searching....
Hi, Joel--
I just ran onto another troubleshooting manual for the Atwood furnace which may seem more readable than the other one I linked to. I'm going to call it the Gary Brinck troubleshooting manual. Both manuals have the sequence-of-operations info Russ mentioned above.
Other thoughts.....
- Several places in the manuals refer to the importance of adequate voltage (as others have mentioned). I'd check voltage at the switch or circuit breaker, hoping to see something in the 12s to the mid-13s. I believe the furnace will start up with very low voltage-- 10.5 or so-- but the motor may not turn fast enough for sustained operation (because of insufficient air flow). Brinck says in practice the furnace may not run below 11.5 v. If you've been testing only on batteries, you'll want to also test on shorepower.
- Both manuals mention high-limit cycling, i.e., low voltage causing the motor to run slow, resulting in overheating and the high-temperature limit switch tripping. The service manual tells us (in the trouble-shooting section) that in rare cases a limit switch can be overly sensitive.
- I'd be curious to know whether there's sooting in the exhaust pipe of your furnace (which Brinck says may indicate insufficient combustion air flow)
- You mention you had an air-flow/limit indication at least once. Did that happen more than once? If so, what were the circumstances?
- You noted that your furnace shut down (after running successfully for a while, I presume) about ten minutes after you put the duct-blank in place. You then removed the blank and the furnace ran successfully. Was there an indication on the control board LED when the furnace stopped (with the blank in place)? And are you sure the thermostat circuit was still calling for heat at that point? (and of course if you still had the thermostat wires twisted together you know it was).
- Any discussion of air flow typically gets into the role of the sail switch. It's role in the startup sequence is to close when the airflow past its vane indicates the motor is up to at least 75% speed. I can't think how it might be involved in the duct-blank situation but you did get at least one fault possibly involving the sail switch. That switch is located behind the motor enclosure half and is relatively easy to access and test (a few continuity tests while you manipulate it should work). You'd also be looking for a bent vane or any kind of fluff hanging off it. And of course you'd be getting a clearer look at the blower wheel while you have that cover off. You can see the sail switch at the 4:45 mark in this video of a similar model. Also, the photo of the 85xx-IV in the Brinck manual shows the sail switch is there.
Edited 9/25 to add:
- you might want to call around to local RV shops to see if they'll test your control board (if the need arises). My local RV shop keeps a tester at the parts counter and tests boards for free. But I'm sure policies vary. Before going in, you might want to research replacement board cost (I'm thinking Amazon and Dinosaur Electronics).
I just ran onto another troubleshooting manual for the Atwood furnace which may seem more readable than the other one I linked to. I'm going to call it the Gary Brinck troubleshooting manual. Both manuals have the sequence-of-operations info Russ mentioned above.
Other thoughts.....
- Several places in the manuals refer to the importance of adequate voltage (as others have mentioned). I'd check voltage at the switch or circuit breaker, hoping to see something in the 12s to the mid-13s. I believe the furnace will start up with very low voltage-- 10.5 or so-- but the motor may not turn fast enough for sustained operation (because of insufficient air flow). Brinck says in practice the furnace may not run below 11.5 v. If you've been testing only on batteries, you'll want to also test on shorepower.
- Both manuals mention high-limit cycling, i.e., low voltage causing the motor to run slow, resulting in overheating and the high-temperature limit switch tripping. The service manual tells us (in the trouble-shooting section) that in rare cases a limit switch can be overly sensitive.
- I'd be curious to know whether there's sooting in the exhaust pipe of your furnace (which Brinck says may indicate insufficient combustion air flow)
- You mention you had an air-flow/limit indication at least once. Did that happen more than once? If so, what were the circumstances?
- You noted that your furnace shut down (after running successfully for a while, I presume) about ten minutes after you put the duct-blank in place. You then removed the blank and the furnace ran successfully. Was there an indication on the control board LED when the furnace stopped (with the blank in place)? And are you sure the thermostat circuit was still calling for heat at that point? (and of course if you still had the thermostat wires twisted together you know it was).
- Any discussion of air flow typically gets into the role of the sail switch. It's role in the startup sequence is to close when the airflow past its vane indicates the motor is up to at least 75% speed. I can't think how it might be involved in the duct-blank situation but you did get at least one fault possibly involving the sail switch. That switch is located behind the motor enclosure half and is relatively easy to access and test (a few continuity tests while you manipulate it should work). You'd also be looking for a bent vane or any kind of fluff hanging off it. And of course you'd be getting a clearer look at the blower wheel while you have that cover off. You can see the sail switch at the 4:45 mark in this video of a similar model. Also, the photo of the 85xx-IV in the Brinck manual shows the sail switch is there.
Edited 9/25 to add:
- you might want to call around to local RV shops to see if they'll test your control board (if the need arises). My local RV shop keeps a tester at the parts counter and tests boards for free. But I'm sure policies vary. Before going in, you might want to research replacement board cost (I'm thinking Amazon and Dinosaur Electronics).
CougarCouple
Senior Member
Good video Old Crow.
Hi everyone, thank you so much for the information. This is a great group! I have done some fiddling with the furnace and thermo and have learned something interesting. When I flip the thermo off switch it confuses the unit and it will not turn back on without touching the thermostat wires together to effectively "jump" the system. After that it seems to work fine with the vent covered or uncovered. To turn the heat off, I turn the slider all the way to cold and it shuts off just fine, then back on when I need it to. When I'm not using the camper I turn off the power and gas so it can't turn on just in case. I've ordered another thermo to see it it really is just defective. Truly I don't know if the issue with the duct blank is solved because the one and only trip we took was a cold night and I didn't want it to shut off so I opened it for the night. Everything worked great which was nice because I really needed to convince my wife that this was a good purchase! I'll keep you posted when the new thermo comes in to see if it really was just faulty.
CougarCouple
Senior Member
Hi Joel H
Sounds like you are making progress. FYI when these Circut boards go into a trouble or fault cycling the power off resets the board.
Didn't you say that was a new stat? Let us know what you find with new stat. Good job on finding that problem, you eliminated several others.
Russ
Sounds like you are making progress. FYI when these Circut boards go into a trouble or fault cycling the power off resets the board.
Didn't you say that was a new stat? Let us know what you find with new stat. Good job on finding that problem, you eliminated several others.
Russ
Old Crow
Searching....
Hmmm. That mechanical thermostat is just two sets of contacts acting together to either complete or interrupt power to the furnace. So flipping the off switch to on (with the slider up above room temp) should be the same as touching the wires together.
If you continue to have inconsistency after the new theromstat, I'd get some electrical contact spray and clean up wire connections at the furnace, pull the control board and clean the contacts with a pencil eraser (and spray the socket side), and check that the ground wire connection is clean. If I remember correctly, ground connection is at the yellow wire at the case, upper right of furnace (if yours is vertically mounted like mine). If symptoms don't change, get the board tested.
Good luck!
If you continue to have inconsistency after the new theromstat, I'd get some electrical contact spray and clean up wire connections at the furnace, pull the control board and clean the contacts with a pencil eraser (and spray the socket side), and check that the ground wire connection is clean. If I remember correctly, ground connection is at the yellow wire at the case, upper right of furnace (if yours is vertically mounted like mine). If symptoms don't change, get the board tested.
Good luck!
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