Dometic Furnace Not Igniting

LDK · 11-12-2021, 02:07 AM

First issue with the furnace on my 2019 Aria 3901.

The fan turns on, tries to ignite, stops after less than 10 seconds. This cycle of trying to ignite occurs 3 times with no luck. Then the fans shuts down. The control board blinks 3 times. I see in the manual that is an Ignition Lockout Fault.

I see some posts talking about replacing the Sail Switch, but given mine "tries" to ignite, I question if it is the Sail Switch.

I did try resetting the furnace at the switch. No luck.

I do hear the "spark" as it tries to ignite.

My hot water heater is working fine so seems propane in general is good.

Have any of you had this issue, and if so how did you fix it? Thank you.

Chateau_Nomad · 11-12-2021, 02:38 AM

Did it just suddenly stop working? Did it work fine before? If you have an absorption fridge, does it light? Does your propane stove work okay? I know you said your hot water works, but check everything. This could be a propane pressure issue caused by a sticky regulator or valve.

I know... Lots of questions. But the idea is to isolate the problem to the furnace. Is your propane tank close to full... or contain at least a decent VERIFIED amount of propane? Have you tried completely closing your propane tank valve, then opening it again?

After answering all those questions, then focus on the furnace itself... possible the control PC board... which can be shorted by getting wet. But check everything else FIRST.

LDK · 11-12-2021, 04:05 AM

Quote:

Originally Posted by Chateau_Nomad

Did it just suddenly stop working? Did it work fine before? If you have an absorption fridge, does it light? Does your propane stove work okay? I know you said your hot water works, but check everything. This could be a propane pressure issue caused by a sticky regulator or valve.

I know... Lots of questions. But the idea is to isolate the problem to the furnace. Is your propane tank close to full... or contain at least a decent VERIFIED amount of propane? Have you tried completely closing your propane tank valve, then opening it again?

After answering all those questions, then focus on the furnace itself... possible the control PC board... which can be shorted by getting wet. But check everything else FIRST.

Thank you!

Yes suddenly stopped working. Worked for 2+ years with zero issues. Last time it worked was 3 days ago.

Only other propane usage in my rig is the on demand hot water heater, and it works fine.

My onboard propane tank is reading a little over 1/4 full. Not sure if that would be considered VERIFIED? I have not tried closing and opening the propane valve, but will try that tomorrow. I will also be filling the propane tank tomorrow.

Have been traveling the NorthWest coast and it pretty much rains every day, so the board getting wet would not be out of the question. Though when I opened the outside panel up today, I did not notice any water penetration.

LDK · 11-12-2021, 04:16 AM

Quote:

Originally Posted by LDK

First issue with the furnace on my 2019 Aria 3901.

The fan turns on, tries to ignite, stops after less than 10 seconds. This cycle of trying to ignite occurs 3 times with no luck. Then the fans shuts down. The control board blinks 3 times. I see in the manual that is an Ignition Lockout Fault.

I see some posts talking about replacing the Sail Switch, but given mine "tries" to ignite, I question if it is the Sail Switch.

I did try resetting the furnace at the switch. No luck.

I do hear the "spark" as it tries to ignite.

My hot water heater is working fine so seems propane in general is good.

Have any of you had this issue, and if so how did you fix it? Thank you.

Update that I tried again, and I am not hearing the ticking sound "spark". So, have a feeling that is at least one, if not the issue.

Jusjay · 11-12-2021, 04:49 AM

Pull the outside cover and check the circuit board. 9 times out of 10 it the issue. If it’s damp try using a hair drying to dry it off. Mind got so wet it had rust spots…

Chateau_Nomad · 11-12-2021, 04:54 AM

An example of "verify" is how a pilot "dips" the airplane's fuel tank - doesn't rely on a mechanical or electronic gauge. So, in your case, actually knowing how much propane is in the tank - realizing that "indicator lights" or the tank's gauge may be inaccurate. When my motorhome was BRAND NEW, the inside panel lights indicated the tank was empty, but the tank gauge read 3/4 full... which was a faulty wiring issue.

After you get your tank filled, check what your tank's gauge and the lights on your inside panel indicate. You KNOW your tank's full - just make sure they all agree.

Then - it's important to try lighting EVERY propane appliance - stove, water heater, furnace. If ONLY the furnace doesn't work, the problem is most likely related DIRECTLY with the furnace.

One last thing... make sure your house battery is charged up so you're getting good DC voltage to the furnace.

Good luck!

abjbrtd · 11-12-2021, 05:34 PM

Take the circuit board out, 2 screws and 1 connector on ours.
Turn it over.
If it looks like this... you'll need one of these.
https://www.dinosaurelectronics.com/
But try contact cleaner first, connector on the board and wire connector and the bottom of the board.

Keep us updated

bgpeters · 11-13-2021, 06:50 PM

A furnace that starts the fan but goes out right away may only have debris on the Sail Switch. Easy to remove, wipe it clean & put it back. That may do the trick for you.

https://www.youtube.com/watch?v=-g3_Y7MqChE

LDK · 11-14-2021, 05:59 AM

Furnace working now. I am not positive why it now works. I was not getting spark from the electrode. I fiddled with the connection on control board that fires the electrode, and it started working.

Reminder when your testing with the outside panel off that the exhaust tube MUST be in place, else the furnace will not stay ignited.

abjbrtd · 11-14-2021, 02:26 PM

Quote:

Originally Posted by LDK

Furnace working now. I am not positive why it now works. I was not getting spark from the electrode. I fiddled with the connection on control board that fires the electrode, and it started working.

Reminder when your testing with the outside panel off that the exhaust tube MUST be in place, else the furnace will not stay ignited.

Very good, thanks for the update

FYI" fiddling often clears/fixes the trouble, less often permanently clears/fixes the trouble

OldWEB · 11-14-2021, 03:21 PM

Quote:

Originally Posted by LDK

Furnace working now. I am not positive why it now works. I was not getting spark from the electrode. I fiddled with the connection on control board that fires the electrode, and it started working.

Reminder when your testing with the outside panel off that the exhaust tube MUST be in place, else the furnace will not stay ignited.

You mentioned you are in the NW coast w/rain so it could be a fair guess the moisture got to the board. What can be done is to remove the circuit board and with a small brush, 'wash' the circuit board with isopropyl alcohol, especially the soldered side. Iso displaces water so it will clean and 'dry' the board... then after some will spray lacquer or other sealants on it. You can also carefully wipe off the HV spark lead with iso. Even a Q-tip swab will work, but iso is the key.
My 2¢

LDK · 11-17-2021, 06:40 PM

Thank you all for the feedback and suggestions!

Hittntherooad · 11-17-2021, 07:53 PM

Quote:

Originally Posted by LDK

Furnace working now. I am not positive why it now works. I was not getting spark from the electrode. I fiddled with the connection on control board that fires the electrode, and it started working.

Reminder when your testing with the outside panel off that the exhaust tube MUST be in place, else the furnace will not stay ignited.

Glad you got it. I keep a spare board for this very reason. The Dinosaur boards are better than OEM.

waynetaylor55 · 11-17-2021, 08:03 PM

I had a similar problem after a particularly violent rainstorm on our drive to Washington state from San Diego. It dried out and worked normally.

I took it a step further by getting some window seal at Home Depot and putting it around the inside of the cover on the indentation in the foam to add a little more weather proofing.

Chateau_Nomad · 11-17-2021, 08:07 PM

Your issue was likely oxidized connections. When you unplugged/replugged connectors you scraped them enough to make contact. Get a tube of electrical grease, like Ox Gard or similar. Keep your connectors well coated with that and you'll never have those problems again. It's also great for battery connectors - just preventive maintenance.

Then, if your PC board is undamaged, seal it with "conformal coating". Any type of conformal electrical circuit board coating will work. Do a google search about it and how to use it. You seal the board and make it waterproof. Then you won't have to keep replacing PCBs that are exposed to weather.

waynetaylor55 · 11-17-2021, 09:10 PM

Quote:

Originally Posted by Chateau_Nomad

Your issue was likely oxidized connections. When you unplugged/replugged connectors you scraped them enough to make contact. Get a tube of electrical grease, like Ox Gard or similar. Keep your connectors well coated with that and you'll never have those problems again. It's also great for battery connectors - just preventive maintenance.

Then, if your PC board is undamaged, seal it with "conformal coating". Any type of conformal electrical circuit board coating will work. Do a google search about it and how to use it. You seal the board and make it waterproof. Then you won't have to keep replacing PCBs that are exposed to weather.

Would this "conformal coating" be useful on other PC boards that might get wet, like the genny, water heater, etc.?

Chateau_Nomad · 11-17-2021, 10:54 PM

Quote:

Originally Posted by waynetaylor55

Would this "conformal coating" be useful on other PC boards that might get wet, like the genny, water heater, etc.?

Absolutely. It's used to seal PCBs exposed to moisture. Some people call it "doping". Many electronics buffs have used several coats of clear fingernail polish for years for this purpose. After it dries, it's basically waterproof.

But coatings designed specific to this purpose likely have a chemical makeup that prevents them from cracking due to temperature changes. Probably an elastomer additive that keeps the coating somewhat soft that is likely not in fingernail polish.

https://en.wikipedia.org/wiki/Conformal_coating

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