Dometic heater

[Barry J]

I have a dometic heater strictly gas, DFLA40211.
When thermostat calls for heat, the fan starts, I hear clicking by no ignition. All breakers are on, all switches are on. All gas valves are turned on. The gas was purged by running the gas stove burner. I took out the sail switch and it was clean. All other components are clean of dust and hair. Could the sail switch be bad or could it be the gas valve that is bad. No gas smell is evident.

[Old-Biscuit]

Fan starts........
Sail Switch is closing otherwise you would not have attempts to ignite (Clicking of spark electrode)
When Sail Switch closes it completes the DC Circuit to Circuit Board
When that DC is applied to circuit board DC is then Sent to Gas Valve AND Spark electrode at same time

IF Furnace hasn't been used in a while it can take several attempts to lite off/prove flame....flow/pressure has to be established
It is only 0.39psi (11"WC ---actually 10.5"WC when gas valve opens)

Give it a few more tries

[Persistent]

Even a wispy spider web in the burner or burner tube can disrupt the gas flow enough to prevent ignition. This is more common in stove burners, but may prevent furnace ignition as well.

[Barry J]

In the past 48 hours I have attempted 10-15 times
Switched on the thermostat..calls for heat…fan turns on… blows cold air,…. No ignition….fan shuts off….
Like I said , system purged , used gas stove throughout weekend, all gas valves open
Still no heat

[Barry J]

Exhaust tube is clean as a whistle

[jl.kauai]

Not familiar with your brand but on the Atwood there is an orifice inside the gas tube that can be removed and cleaned. Soak in rubbing alcohol for 15-20 mins. Don’t put anything into opening just blow out. When you replace it do not over tighten. Good luck. Travato John

[Old-Biscuit]

Originally Posted by jl.kauai

Not familiar with your brand but on the Atwood there is an orifice inside the gas tube that can be removed and cleaned. Soak in rubbing alcohol for 15-20 mins. Don’t put anything into opening just blow out. When you replace it do not over tighten. Good luck. Travato John

Dometic is Atwood......Dometic acquired them many years ago then few years ago dropped Atwood Name and Branded their stuff as Dometic (DFLA40211----Dometic Furnace Large AC 40Kbtu. **120VAC power to 24VAC transformer

OP..check that gas valve is getting 24VDC from circuit board during trial for ignition sequence. ***ON/OFF Switch not tripped on red wire from circuit board to gas valve
No DC......bad circuit board
Got DC....clogged orifice or bad gas valve

Installation/Operation/Wiring (pg 23 Fig 3 & 4)
https://www.lancecamper.com/docs/man...-Series-IM.PDF