No Heat Designation on Dometico Heater

[rspecialk]

I have a 2016 Classic Airstream. I was experimenting this weekend with the heater. It is sunny at 45 degrees here. The AS is winterized and in the driveway. I thought I would try out the heater. I plugged the AS into a 15 amp service and lights in AS work. I know the heater runs of LPG but thought there may need a bit of charge for the Dometico display and maybe a starter. The Dometic display worked and I then went through the modes to identify HEAT. It didn't show up. I got, COOL, AUTO, HP and FAN but no heat. I know I have seen HEAT before when I scrolled through but had never tried it because it was never that cold. It as if the HEAT designation evaporated. I tried AUTO and it would cycle on for about 30 seconds and then off. I waited for about 5 minutes and then shut the whole unit off for fear of blowing something. I pulled out the owners manual but they simply listed the modes and there was no discussion of HEAT mode being removed. Any advice or things to try?

[fran&frank]

If you have two airconditioners then your thermostat has two zones, and the furnance only shows up on one of them. So try changing zones then cycling throught the modes again and I'll bet you'll finf FURN.-- Frank

[rspecialk]

Thank you Frank. I learned something new. Unfortunately, even once located, the heater cycled on and off. I had my mechanically inclined brother-in-law stop over and he tried all his tricks. He thought maybe there was air in the LP lines so he bleed the lines and that didn't work. Still cycled on and off. He thought maybe the thermocoupler is bad. Will add to list of things that need to be fixed unless you have another suggestion.

[Al and Missy]

If the furnace doesn’t light it will try three times and then fault. To clear the fault you have to reset the furnace either by turning it off and back on at its master switch behind the outside panels or turn the 12 volt power off and back on with the USE/STORE switch.

When the furnace tries to light, it does the following:
1. Turns on fan
2. Runs fan for a while to clear any unburned propane from the combustion chamber
3. Turns on the propane. You should hear a click and you might be able to smell propane in the outside exhaust
4. Sparks to light the propane
5. Senses the propane burning and continues running until the thermostat says to turn off or,
6. If not sensing burning shuts off and retries the process two more times.

Where in the process it stops is a clue as to what is wrong.

Al

[rspecialk]

Al:

Your post is spot on. It went exactly as you said. I heard it try and light and then go off and then it went through the process two more times and then shut off. Since it goes through all the cycles, would you guess the thermocoupler? Maybe there isn't a thermocoupler. It just doesn't light and heat. I have a shower I am taking to to get fixed as well as the awning so I can add to the list.

Thanks for troubleshooting. Your run down was very helpful and easy to follow.

[azflycaster]

I had the same issue with my 02 hydro flame furnace. A new circuit card did not fix it, but a new igniter did.

[Hardman]

Try changing zones then cycling throught the modes again.

[Sid Arthur]

We had the same problem when we ran out of LPG. Refilled the tanks: nothing. Re-started, recycled over and over: nothing. Ultimately we removed the cover OUTSIDE and found a RESET switch. That switch reset the igniter system. Once turned off, then back on, the FURN (in ours it only exists in Zone 2) finally ignited and we got heat, not just blowing (cold) air. If THAT doesn't work, you may need to replace the igniter.

[Al and Missy]

Originally Posted by rspecialk

Al:

Your post is spot on. It went exactly as you said. I heard it try and light and then go off and then it went through the process two more times and then shut off. Since it goes through all the cycles, would you guess the thermocoupler? Maybe there isn't a thermocoupler. It just doesn't light and heat. I have a shower I am taking to to get fixed as well as the awning so I can add to the list.

Thanks for troubleshooting. Your run down was very helpful and easy to follow.

In my case I changed the board and it didn't help. My furnace does not have a thermocouple. Somehow the igniter senses the heat. In my case it was the igniter. If you haven't already solved the problem, try to determine if it is sparking. Pull the wire from the igniter off of the coil on the control board and hold another wire connected to ground near the terminal while it is going through the sequence. If it is not sparking you have a bad control board. If it is sparking you have two possibilities - bad igniter or no propane. Run it through the sequence again and see if you can smell propane in the furnace exhaust. If you can, it is definitely the igniter. If not it could be the gas valve or for some reason you are not getting gas to the valve.

Al

[OTRA15]

Originally Posted by rspecialk

. . .
Any advice or things to try?

Did you get this 11/23/19 problem sorted out? Maybe try a hard re-boot of the stat, per the Dometic manual.

https://www.google.com/search?q=Dome...=airforums.com

Any error codes on the stat, like a bad sail switch maybe?

Good luck,


Peter