Furnace and Heat Pump Failures in Cold Weather: Troubleshooting a 2021 3121RL

[jjwhite368]

Not a good time for heat to quit. We run a 2021 3121RL with Legacy SO we also have iNCommand. First our furnace failed to fire. It would run fan, open gas valve and attempt to light. No fire. I spent the day diagnosing, part replacement. No progress (igniter checked out, sail switch OK, control board ok, plenty of propane) we also have and still have screen over furnace chimney.

NOW problem#2, the rear A/C (heat pump) is no longer responding to iNCommand communications. So with real cold weather around, we are left with the ‘fire place’ and 2 ceramic heaters.

Any suggestions are welcome.

 

[MandK]

You say it opens the gas valve and attempts to light.
Can you smell propane and hear the igniter clicking when the gas valve opens when standing near the exhaust?
If yes, probably the igniter electrode.
I had to put 3 of them on my ‘21 3121.

I don’t know anything about in command, sorry.

 

[jjwhite368]

Yes, you can smell gas and it is clicking. The electrode is new.

 

[ChuckS]

In Command and Zone 2 AC... I would do a HARD RESET... turn display off.. remove battery power AND shore power ( converter supplies 12 vdc all the time to AC gateways)... wait a minute or two then aply 12 vdc and shore power ... bring up the in command display and see Zone 2 now responds... doing a hard reset will often clear a "latched relay" on the gateway box....

Furnace --- you stated you replaced ignitor... did you set gap at 1/8 inch? also what was the condition of the burner assy when you removed it to replace ingnitor? ... if it is rusted up, etc you can try to clean the perforation holes out, etc or replace burner section.... If burner is good, gas valve opens and ignitor fires then the furnace board is not seeing the flame .. replace board

 

[jjwhite368]

Will do the hard reset. We replaced the igniter through the outside. Heater was not physically removed in order to replace it. Old igniter looked identical (no rust or soot on electrodes).

 

[MandK]

I agree with ChuckS. Just in case there is some confusion, you have to remove the burner to replace the electrode. You mentioned above that the board is good but you could remove the burner again, check the 1/8” gap and then before reinstalling the burner assembly, ground it to the chassis of the furnace and try to start the furnace. Watch for the ignition sparks in the gap. If there is no spark, I would suspect the board. I had to replace mine at one point. I used a Dinosaur board, available at Amazon and others.

 

[jjwhite368]

Hard reset as described above completed. No change. Little button in center of main iNCommand board pressed. It reset, no change in getting rear a/c (heat pump) to come on.

Igniter was tested prior to installation yesterday and arc was noted between electrodes.

 

[MandK]

OK. Well, everything mentioned is the extent of my experience to get mine running, hopefully others can help. Good luck and let us know what the gremlin was.

 

[jjwhite368]

Thanks, will do. Ticket submitted to ASA (iNCommand). Hopefully they can use Global Connect to check comms to the zone 2 a/c.

Plan is to pull the furnace Monday after it warms up here and check the burn chamber or take it to be bench tested.

 

[ChuckS]

Since you did a hard reset and zone 2 still not responding does it...
Indicate an actual temperature plus your set point ( two readings )?
** If you are seeing a ( -F ) on the display then the gateway or control module has no 12 vdc due to a loose connection at gateway or AC control board or has failed

If there is an actual temp reading from zone 2 then try just that AC using fan only and see if AC responds

If yes then you know the BCM , Display, gateway, and AC control module are all talking to each other

I'd also check the AC 120 circuit breaker ( turn it off and back on ) and see if any change..

** Usually if there is a CANBUS Comm error, etc the In Command would should an error code... but you didn't indicate any..

 

[jjwhite368]

OK news flash, you must have the furnace outside switch on (reset) for 12v power to get to the zone 2

 

[ChuckS]

OK news flash, you must have the furnace outside switch on (reset) for 12v power to get to the zone 2

I cannot imagine why in the world they would wire the Zone 2 AC control box and gateway 12 vdc thru the furnace reset switch on the furnace case... I would be rewiring that myself down the road to another 12 vdc circuit in the power center panel... Very nice troubleshooting,.

Gather all is well now

 

[jjwhite368]

friends of mine were with me at the 25 rally and were working on another Montana and found the same thing.

 

[jsb5717]

So did you get the furnace running? On one occasion with symptoms like yours, I found that our burner was rusted out. The center was no longer solid with evenly spaced holes...it was just one big hole. Propane was present and it tried to ignite, but it couldn't. A new burner solved it in that situation.

On another occasion the symptoms were similar except the furnace would fire then immediately go out. That one turned out to be the main propane regulator. There is a certain flow required by the furnace for it to function correctly. A faulty regulator can reduce that flow so that the furnace can't sustain a burn even though the other gas appliances might still work just fine.

These furnaces can be finicky. I've replace several parts on ours over the years and I now carry virtually every replaceable component so I can troubleshoot and repair rather than just be stuck.

 

[twindman]

I had trouble with the furnace, I think (maybe the stove) one time. A burner would light on stove but not two (or else the furnace didn't work). Anyway, it was the crossover regulator on the passenger side. Had pressure but not enough for everything to work. So I guess either regulator would mess up the furnace......

 

[jjwhite368]

UPDATE - 1. We have HEAT. 2. We removed the gas valve module even though we heard it open and smelled the propane odorant. There was a significant accumulation of rust inside the fire box and the burner. We replaced the burner and the valve (why not, we already replaced everything else. Re-assmbled, checked gas line for leaks, it fired right up.

FYI- Dometic has discontinued the part which is the mounting bracket for the propane valve, igniter and burner assembly. It is no longer in the parts catalogue. Mine was rusted on the burner side. I cleaned it with an Emory cloth and painted it with high-heat resistant rustoleum prior to re-assembly.

BONUS - in examining how to remove the entire unit, I exposed the back by removing the panels of the storage bay and the bottom panel of the pantry. I found one of the flex-ducts not completely connected to the back of the furnace. That is now fixed as well.

Thanks everyone for your ideas and encouragement. You continue to be THE go-to source for D-I-Y assistance. FYI#2 - even Grok recommends referring to the MOC forum for answers!

 

[jjwhite368]

Last post - I had submitted a ticket to ASA Electronics (iNCommand) when we were investigating the connection between the heat pump (zone 2 a/c) and the furnace. This morning my in box was full of .pdf s with exact documentation of the comms box on the heat pump including wiring and the CAN network. Very helpful and now in my library.

 

[Carl n Susan]

How about loading those PDFs in to the Files section here so we can all see them? Click on RESOURCES in the blue bar above and then one of the file CATEGORIES in the left pane.

 

[Daryles]

When you take down your basement wall, you will find a heater duct laying on the floor back there. Take this duct and route it down the hole where your plumbing goes to the holding tanks. Point it down and aft as far as you can. This will put heat into your underbelly towards your dump valves to help prevent freezing valves, tanks and plumbing.
Take Gorilla tape and seal up any holes around your frame. This will stop Drafts and help keep you warmer.

 

[Jfm49]

Not a good time for heat to quit. We run a 2021 3121RL with Legacy SO we also have iNCommand. First our furnace failed to fire. It would run fan, open gas valve and attempt to light. No fire. I spent the day diagnosing, part replacement. No progress (igniter checked out, sail switch OK, control board ok, plenty of propane) we also have and still have screen over furnace chimney.

NOW problem#2, the rear A/C (heat pump) is no longer responding to iNCommand communications. So with real cold weather around, we are left with the ‘fire place’ and 2 ceramic wheaters.

Any suggestions are welcome.

Not a good time for heat to quit. We run a 2021 3121RL with Legacy SO we also have iNCommand. First our furnace failed to fire. It would run fan, open gas valve and attempt to light. No fire. I spent the day diagnosing, part replacement. No progress (igniter checked out, sail switch OK, control board ok, plenty of propane) we also have and still have screen over furnace chimney.

NOW problem#2, the rear A/C (heat pump) is no longer responding to iNCommand communications. So with real cold weather around, we are left with the ‘fire place’ and 2 ceramic heaters.

Any suggestions are welcome.

We had same issue with our furnace, tried everything. We were camping at 8,300 feet. Turn gas regulator counter clockwise 5 turns. Furnace fired just fine. When we got back down to 3,000 feet turned regulator clockwise 5 turns, furnace worked fine.