Help me understand AS HVAC

[FilmGuy]

We just bought a 2018 International Serenity 23FB. Our previous Airstream was a 2000 Bambi. There’s been quite a lot of technology upgrades!

The 2018 has an issue with its HVAC system, and I’m trying to understand just how this new system is supposed to work.

The furnace was working when I inspected the trailer, but the thermostat showed an E1 error. When I got the rig home, the furnace wouldn’t come on at all. (I can’t tell if the AC works; I’m in Maine, and it’s much too cold for air to come on here at the moment.) It doesn’t show up on the thermostat’s mode selections. The MODE switch cycles through OFF, COOL, FAN and back to OFF. HP and FURN never show up.

Some reading on the forum, discussions with Dometic tech support, and work cleaning connections has me convinced that I need a new control board for the AC unit (which are pretty scarce, it seems), but I have two questions (I have more, but these are the big ones.)

1. Am I missing anything obvious?

2. Is there any way for the furnace to work if the AC control board is bad? Or is the system just that integrated now?

[TitusNW]

The Dometic thermostat manual I have says E-1 is loss of communication and also shows a reset procedure. See attached


These are notes I've saved from the forum:


Furnace Trouble Shooting

Inside:
Check furnace fuse
Reset trailer battery disconnect switch. (Off-wait-On)

Outside:
Remove 4 screws
Look at blinking light:

1: Airflow/Limit Switch
2: Flame Sense fault
3: Ignition lockout
Steady ON: Internal controller error

Reset breaker switch near control board

Fingers crossed it starts

https://www.airforums.com/forums/f42...er-232456.html

[Wazbro]

Have you reset the thermostat?

I believe you can't run the furnace without the AC control board, unless you can figure out a way to connect a separate thermostat directly to it.

[FilmGuy]

Originally Posted by Wazbro

Have you reset the thermostat?

I believe you can't run the furnace without the AC control board, unless you can figure out a way to connect a separate thermostat directly to it.

Yes. I’ve reset it and powered everything down and back up and reset it again. Same result. The Heat Pump and Furnace modes never show up.

Thanks for the confirmation on the AC board being essential. That’s what I thought, but wanted to be sure I wasn’t on a wild goose chase.

[FilmGuy]

Originally Posted by TitusNW

The Dometic thermostat manual I have says E-1 is loss of communication and also shows a reset procedure. See attached


These are notes I've saved from the forum:


Furnace Trouble Shooting

Inside:
Check furnace fuse
Reset trailer battery disconnect switch. (Off-wait-On)

Outside:
Remove 4 screws
Look at blinking light:

1: Airflow/Limit Switch
2: Flame Sense fault
3: Ignition lockout
Steady ON: Internal controller error

Reset breaker switch near control board

Fingers crossed it starts

https://www.airforums.com/forums/f42...er-232456.html

Thanks for this. I think (hope?) the furnace is actually OK. It was running and doing a great job when I picked the trailer up. But it’s great to have this check list for if it turns out not to be.

[Hermes]

Originally Posted by Wazbro

Have you reset the thermostat?

I believe you can't run the furnace without the AC control board, unless you can figure out a way to connect a separate thermostat directly to it.

Had (still have) a very similar E1 problem. Waiting for the control board. Since we camp/travel in Winter, I installed a good old fashion and reliable spring thermostat (White Rogers) to control the furnace, works just fine. Will be going to the dealer to fix the Dometic system for the AC in the Spring.

I have cleaned (contact cleaner) the contacts and applied a thin coating of dialectic grease with a Q tip (they run the cables in the AC ducts which can be very humid). I also re-crimpted the 11 RJ11 connectors (inappropriate for this kind of use in RVs bouncing down highways) and replaced the RJ11 connector that connected the thermostat since the wire was somewhat twisted, just to be safe. I also bought a new CCC2 thermostat to see if that was the problem. Things worked for a while but the E1 error came back. In fact the system can work fine in the morning and by the afternoon the error will reappear, without moving the trailer an inch.

They install the same Dometic system in Tiffins, Newmars and I have seen Prevosts with it (4 AC units... lots of flimsy RJ11 connectors!). At least we won't freeze now with the furnace's own reliable thermostat.

[jgomez888]

I had a new unit installed and the furnace option did not display in the thermostat and couldn’t be selected. This sounds the same. In the top unit, there are dip switches that have to be set on/off in a certain order to configure the AC, heat pump, furnace options. The dealer that installed the AC did not set them correctly initially, but did correct the dip switch order to correct it.

[FilmGuy]

Originally Posted by jgomez888

I had a new unit installed and the furnace option did not display in the thermostat and couldn’t be selected. This sounds the same. In the top unit, there are dip switches that have to be set on/off in a certain order to configure the AC, heat pump, furnace options. The dealer that installed the AC did not set them correctly initially, but did correct the dip switch order to correct it.

The dip switches are all in the proper place, but I don't know anything about the mechanics of dip switches, and it's worth considering whether they can just lose their connection? I might try flipping them back and forth a time or two and see if it shakes anything loose.

[FilmGuy]

Originally Posted by Hermes

Had (still have) a very similar E1 problem. Waiting for the control board. Since we camp/travel in Winter, I installed a good old fashion and reliable spring thermostat (White Rogers) to control the furnace, works just fine. Will be going to the dealer to fix the Dometic system for the AC in the Spring.

I have cleaned (contact cleaner) the contacts and applied a thin coating of dialectic grease with a Q tip (they run the cables in the AC ducts which can be very humid). I also re-crimpted the 11 RJ11 connectors (inappropriate for this kind of use in RVs bouncing down highways) and replaced the RJ11 connector that connected the thermostat since the wire was somewhat twisted, just to be safe. I also bought a new CCC2 thermostat to see if that was the problem. Things worked for a while but the E1 error came back. In fact the system can work fine in the morning and by the afternoon the error will reappear, without moving the trailer an inch.

They install the same Dometic system in Tiffins, Newmars and I have seen Prevosts with it (4 AC units... lots of flimsy RJ11 connectors!). At least we won't freeze now with the furnace's own reliable thermostat.

There's a lot to recommend the idea of a simpler thermostat for the heat. We live in Maine, so heat is a lot more important to us than Air. Where did you locate it?

How long are they telling you it will be before the board is available? They seem pretty scarce just now.

I'm kind of convinced that the location of the control board on the roof is just plain dumb. Especially for those of us who live where it snows. Or rains. Or near the ocean where you get that nice sea air. Or... pretty much any place but the desert. Put a delicate but important bit of electronics with a dozen connectors on the roof of an RV and drive it down the road in the rain. What could possibly go wrong?

[Hermes]

In the 28' RB model, the furnace is on the floor under the sink cabinet, so a short (5') pair of wires connect the furnace (with quick connect connectors which I can disconnect if I want) to the thermostat placed on the side of the sink counter cabinet. I already had my MPPT solar controller display screen there so they are side by side.

The two wires (blue) from the AC control board are no longer connected to the furnace, but they have the quick connectors, so I can reconnect them if need be in the future (but based on our use of the manual thermostat this winter, that seems unlikely).

Dometic has to understand that heating is not an option when you travel/camp in the winter months, even in the SW or California as we are seing this winter!!

You need to be able to trust your equipment, and simpler is better.

[Boxite]

Gotta wonder…why they call this new technology an “upgrade”….

[Wazbro]

Originally Posted by Boxite

Gotta wonder…why they call this new technology an “upgrade”….

Technology is great! When it works.

[starlite29]

Just making sure you’ve seen my troubleshooting guide on this issue:

https://www.airforums.com/forums/f42...de-224933.html

It’s probably the control board but going through the steps will help you confirm.

[FilmGuy]

Originally Posted by starlite29

Just making sure you’ve seen my troubleshooting guide on this issue:

https://www.airforums.com/forums/f42...de-224933.html

It’s probably the control board but going through the steps will help you confirm.

I have your guide printed out. Thank you so much for doing it. It was/is very helpful. I’ve found and cleaned all of the RJ11 contacts, but did not re-crimp them.

[FilmGuy]

I wanted to follow up and say that with this forum’s help—especially the excellent troubleshooting guide by starlite29—I’ve got this issue resolved. After cleaning all the RJ11 and sensor connections with no success, I was fairly sure the issue was a failed control board in the AC unit on the roof. I was able to source a replacement board, and swapping that out completely resolved the issues.

I have heat!! Too cold yet to test the AC, but it shows up on the thermostat as it should, and I’m optimistic. 🙂

Thanks to all who responded for your help.