Still no working furnace in my brand new coach after 10 months!

[TimmyB]

Originally Posted by Fiesta48

I gave up on my heat pumps. We just use $20 space heaters now. Too expensive to maintain and replace heat pumps. 1 gave up but still works as A/C.

Ours has done a decent job so far, but I'm with you. I'll burn through a few portable $30 units before worrying about trying to fix something for four figures!

Thanks.

[Argosy]

You're welcome, I hope it helps you long term.

FWIW it was a BIG job to find this. As this will be the third time you've had it in and knowing what they might have to do to find the problem I'd try to talk a little sense to them and "encourage" them to save time and money by replacing the furnace. Dometic is going to cover the cost of a new furnace, maybe the labor to replace it. At this point it doesn't make sense to keep trying to repair a problem they didn't create and are having a very difficult time finding.

Good luck!!

[TimmyB]

Originally Posted by Argosy

You're welcome, I hope it helps you long term.

FWIW it was a BIG job to find this. As this will be the third time you've had it in and knowing what they might have to do to find the problem I'd try to talk a little sense to them and "encourage" them to save time and money by replacing the furnace. Dometic is going to cover the cost of a new furnace, maybe the labor to replace it. At this point it doesn't make sense to keep trying to repair a problem they didn't create and are having a very difficult time finding.

Good luck!!

Yeah, I plan on calling the service manager about this in the coming days and let him know of your experience. Thanks, again.

[Charlie 5320]

You need to know the sequence of operation. It was in one of the earlier posts. You need a volt meter to check this out yourself. All the system does is call for heat, makes a switch between the r and w circuit on the furnace control board. R is 12v power and the W is the heat circuit on the control board. There should be a schematic for the furnace on the door or some where. Anyways, when the stat calls for heat it switches power to the W terminal on the board. The blower will start, close the sail switch, then the ignition will cycle, probably be a spark, you may or may not be able to hear, then the gas valve will open. The furnace will light , and if the control board isn't grounded thru the flame in so many seconds, it will go thru a retrial. MAKE SURE THE BOARD IS GROUNDED. Turn the stat up should be 12v + on the meter if not have to find out why. If 12v + move to the next item, sail switch, should be 12v + on both sides of the switch. If you do this test right after the furnace shuts off you will find out what the problem is. If you have 12v + on the sail switch move to the limit switch, verify that switch is working.

[TimmyB]

Originally Posted by Charlie 5320

You need to know the sequence of operation. It was in one of the earlier posts. You need a volt meter to check this out yourself. All the system does is call for heat, makes a switch between the r and w circuit on the furnace control board. R is 12v power and the W is the heat circuit on the control board. There should be a schematic for the furnace on the door or some where. Anyways, when the stat calls for heat it switches power to the W terminal on the board. The blower will start, close the sail switch, then the ignition will cycle, probably be a spark, you may or may not be able to hear, then the gas valve will open. The furnace will light , and if the control board isn't grounded thru the flame in so many seconds, it will go thru a retrial. MAKE SURE THE BOARD IS GROUNDED. Turn the stat up should be 12v + on the meter if not have to find out why. If 12v + move to the next item, sail switch, should be 12v + on both sides of the switch. If you do this test right after the furnace shuts off you will find out what the problem is. If you have 12v + on the sail switch move to the limit switch, verify that switch is working.

Thanks. I appreciate the help.

[Dutch Star Don]

I would go about this differently. I would call Precision Circuits and let one of their techs go through the system with you on the phone. Don't be afraid to explain to them that you need them to speak in plain English, not techno speak.

They may know exactly what is wrong and send you what you need.

[TimmyB]

Originally Posted by Dutch Star Don

I would go about this differently. I would call Precision Circuits and let one of their techs go through the system with you on the phone. Don't be afraid to explain to them that you need them to speak in plain English, not techno speak.

They may know exactly what is wrong and send you what you need.

I've already tried that. After talking with their tech, he was convinced that it could not be their control, simply because of how little their system does in the process of turning the furnace on our off. I'm planning on calling the service manager for REV next week and discussing the plan of attack.

Thanks for helping!

[Charlie 5320]

Originally Posted by Dutch Star Don

I would go about this differently. I would call Precision Circuits and let one of their techs go through the system with you on the phone. Don't be afraid to explain to them that you need them to speak in plain English, not techno speak.

They may know exactly what is wrong and send you what you need.

And you would be wasting your time and their time. I've been in the HVAC field for 30 years and can't tell him where the problem is with out seeing the furnace. I would know where the problem is by watching the furnace one time most likely. The SYSTEM IS working, it IS telling the furnace to run. The problem IS in the furnace, period.

[TimmyB]

Originally Posted by Charlie 5320

And you would be wasting your time and their time. I've been in the HVAC field for 30 years and can't tell him where the problem is with out seeing the furnace. I would know where the problem is by watching the furnace one time most likely. The SYSTEM IS working, it IS telling the furnace to run. The problem IS in the furnace, period.

I understand your sentiment, Charlie, but I'm not convinced for one VERY strange reason. When the issue happens, it not only happens to the furnace, it causes the rooftop heat pump/AC unit to stop working. The sequence of events is exactly as it should be for the first 10-15 minutes. Then, not only does the burner stop (while the blower continues), but the rooftop heat pump/AC unit, which was running perfectly for the past 10 hours with constant fan on whether there was a call for heat or not, suddenly stops. No fan running.

You being in the business for all of that time, maybe you can help me. What is there that when the issue happens, it causes a malfunction with BOTH the furnace and the rooftop AC unit? I'm totally without even a guess.

Thanks for any wisdom you can share my way!

[Old Scout]

….haven't reviewed the whole thread but for most Dometic systems with a heat pump, there are three main components that must work in concert--the furnace, the heat pump and the thermostat. Somewhat beyond the obvious that all three have to be compatible and function properly, is that the dip switch config on the heat pump must be set correctly to support the furnace, eg, at low ambient temps [mid to low 30s] the heat pump locks out and the thermostat then starts the furnace automatically. Sorry if I missed it, have you already investigated and confirmed the dip switch settings?

[Charlie 5320]

Originally Posted by TimmyB

I understand your sentiment, Charlie, but I'm not convinced for one VERY strange reason. When the issue happens, it not only happens to the furnace, it causes the rooftop heat pump/AC unit to stop working. The sequence of events is exactly as it should be for the first 10-15 minutes. Then, not only does the burner stop (while the blower continues), but the rooftop heat pump/AC unit, which was running perfectly for the past 10 hours with constant fan on whether there was a call for heat or not, suddenly stops. No fan running.

You being in the business for all of that time, maybe you can help me. What is there that when the issue happens, it causes a malfunction with BOTH the furnace and the rooftop AC unit? I'm totally without even a guess.

Thanks for any wisdom you can share my way!

With out seeing the schematic for the system, it's just a guess, but. The heat pump is supposed to run first on most systems and IF it can't satisfy the call for heat in a length of time, the gas furnace will come on to satisfy the call and they BOTH shut down, when the call for heat is satisfied. Do you have the heat pump blower on auto or manual? Now your system most likely will have an outdoor stat the should keep the heat pump out of the circuit below a certain temp.

To test just the furnace, remove the wire from the R terminal on the furnace control board. Hook up a jumper wire from the R terminal to the W terminal, this will place a call for heat and the furnace SHOULD light and run till you remove the jumper wire. If it does NOT, the problem IS in the furnace. Then you have to trouble shoot the furnace. IF the furnace does work correctly, there may be a problem with the data cable on your system. I had that on my Dolphin a couple years ago, but I didn't have heat pumps to contend with.

[Charlie 5320]

Originally Posted by Old Scout

….haven't reviewed the whole thread but for most Dometic systems with a heat pump, there are three main components that must work in concert--the furnace, the heat pump and the thermostat. Somewhat beyond the obvious that all three have to be compatible and function properly, is that the dip switch config on the heat pump must be set correctly to support the furnace, eg, at low ambient temps [mid to low 30s] the heat pump locks out and the thermostat then starts the furnace automatically. Sorry if I missed it, have you already investigated and confirmed the dip switch settings?

Good comment, being this is a new coach, the setup could be where the problem is. Problem is, when he took the coach back for repair they just thru a new control board on it and let it go. Parts changers rarely have any idea how to repair.

[TimmyB]

Originally Posted by Charlie 5320

With out seeing the schematic for the system, it's just a guess, but. The heat pump is supposed to run first on most systems and IF it can't satisfy the call for heat in a length of time, the gas furnace will come on to satisfy the call and they BOTH shut down. Now your system most likely will have an outdoor stat the should keep the heat pump out of the circuit below a certain temp.

To test just the furnace, remove the wire from the R terminal on the furnace control board. Hook up a jumper wire from the R terminal to the W terminal, this will place a call for heat and the furnace SHOULD light and run till you remove the jumper wire. If it does NOT, the problem IS in the furnace. Then you have to trouble shoot the furnace. IF the furnace does work correctly, there may be a problem with the data cable on your system. I had that on my Dolphin a couple years ago, but I didn't have heat pumps to contend with.

In the PCI board, they are two separate systems with two separate sensors (heat pump sensor in bedroom, furnace sensor in living room). I can (and most often, do) have them on separately. Since we have no "reliable" heat from the furnace, on a cold night (55 or below), we'll just put the rooftop heat pump on at about 67 with fan on constant HIGH. She works like she's supposed to the entire night. Only if I get up in the morning and try to warm the living room up with the gas furnace do I get any issue with the rooftop heat pump unit, and it only happens when the furnace has the issue. It takes 15 to 20 minutes to manifest itself, but it almost always does.

[TimmyB]

Originally Posted by Old Scout

….haven't reviewed the whole thread but for most Dometic systems with a heat pump, there are three main components that must work in concert--the furnace, the heat pump and the thermostat. Somewhat beyond the obvious that all three have to be compatible and function properly, is that the dip switch config on the heat pump must be set correctly to support the furnace, eg, at low ambient temps [mid to low 30s] the heat pump locks out and the thermostat then starts the furnace automatically. Sorry if I missed it, have you already investigated and confirmed the dip switch settings?

No, I have no idea where to even look for these dip switches? Where might I find them?