Dometic HVAC acting wonky

[Mark and Lorraine]

Update on furnace not working below 45 degrees.

Ended up being a faulty thermostat wire.

Originally, the thermostat had an error code of E1 when we turned on the furnace during our first cold morning this fall. I rebooted the system, the error code went away and the furnace then worked fine above 45 degrees, and below 45 would cycle with the burner only staying lit for 5 seconds. This would repeat a few times during a 20 minute period with the blower running the whole time, then turn off completely. There where no error codes on the furnace circuit board. Then it just stopped working completely until the temps warmed. Finally it just stopped responding completely.

Kudos to the service manager at the local rv dealer for an evaluation and repair. He talked with an Oliver tech who described the rather difficult process of running a new wire as the continuity was broken on 2 of the 3 wires running up to the AC. This apparently has infrequently occurred where the wire is pinched between the hulls during assembly. 

In this case, the wire was compromised and during cold weather the wire contracted enough to short. Then after more miles were driven the wire severed.

I’m very happy to have established a strong service relationship locally. It was interesting that the local dealer was skeptical of the brand as it was the first one they worked on, but very complimentary after completing the work and engaging Oliver’s service department with constructive dialog to resolve the problem.

Dometic HVAC system.

Mark
Hull 1111
Chelsea MI

[Rivernerd]

I note your post notes work on an Oliver with a Dometic furnace, and you list "Hull 1111" under your name.  But, your automatic signature block says "soon to be Elite II owners." 

Do you need to update your auto signature, or are you upgrading from an Elite I to an Elite II?

[Mark and Lorraine]

Update- thx

[Bill and Nancy]

2 hours ago, Mark and Lorraine said:

Update on furnace not working below 45 degrees.

Ended up being a faulty thermostat wire.

Originally, the thermostat had an error code of E1 when we turned on the furnace during our first cold morning this fall. I rebooted the system, the error code went away and the furnace then worked fine above 45 degrees, and below 45 would cycle with the burner only staying lit for 5 seconds. This would repeat a few times during a 20 minute period with the blower running the whole time, then turn off completely. There where no error codes on the furnace circuit board. Then it just stopped working completely until the temps warmed. Finally it just stopped responding completely.

Kudos to the service manager at the local rv dealer for an evaluation and repair. He talked with an Oliver tech who described the rather difficult process of running a new wire as the continuity was broken on 2 of the 3 wires running up to the AC. This apparently has infrequently occurred where the wire is pinched between the hulls during assembly. 

In this case, the wire was compromised and during cold weather the wire contracted enough to short. Then after more miles were driven the wire severed.

I’m very happy to have established a strong service relationship locally. It was interesting that the local dealer was skeptical of the brand as it was the first one they worked on, but very complimentary after completing the work and engaging Oliver’s service department with constructive dialog to resolve the problem.

Dometic HVAC system.

Mark
Hull 1111
Chelsea MI

Mark where does the error code show up?

[Mark and Lorraine]

On 12/5/2022 at 4:43 PM, Bill and Nancy said:

Mark where does the error code show up?

The error code was displayed on the thermostat. Sorry I didn't see this sooner.

[MHCamper]

Hello everyone,

I'm grateful for this community and especially for the helpful post from Mark and Lorraine. Their experience mirrored the issues we had with our intermittent furnace. I wanted to share our solution in case it helps others: it was a faulty thermostat-to-AC wire.

Symptoms:

• Below ~60°F:

  • Furnace blower would start, ignite briefly, and then shut off after a few minutes.
  • Blower would start, ignite, then immediately go out.
  • Blower would start with no ignition.
  • In each case, I heard a "click" from a relay in the AC, followed by another "click" as the system shut down. The blower would then enter shutdown mode.
  • Oddly, stepping on a specific spot near the pantry/seat seemed to trigger the on/off cycle.

• Above ~60°F:

  • Furnace worked perfectly with no issues.

The Fix:

Initially, I suspected temperature-related components and replaced the gas regulator switchover valve and upper-limit switch. This did not resolve the problem, so I changed the sail switch, control board, and thermostat, just to throw everything at it. (I now have spare parts on the ready)

After finding Mark and Lorraine’s post, I confirmed their diagnosis: a faulty thermostat-to-AC wire. Here’s how I fixed it:

1. Purchased an 18-3 wire from Home Depot.
2. Removed the interior AC cowling to locate the thermostat wire’s connection to the HVAC control unit.
3. Disconnected the thermostat and connected a new wire directly to the HVAC control box using compact splicing connectors.
4. I tested it with this jumper and it worked as expected, without issue.
5. Fished the new wire with a wire hanger from the HVAC towards the curb side (opposite of factory wire routing), back to the rear compartment, over to the street side, behind the radio and pantry, then down to the thermostat. It was actually really easy to fish the wire around.

Once completed, the furnace worked flawlessly, even in cold temperatures, regardless of where I stood inside or outside the trailer.

I hope this helps someone else!

[Mark and Lorraine]

It’s interesting to me that hull 1108 and hull 1111 both experienced the same issue. 
Having a source for owners to share their knowledge and experiences rocks!