Dometic DF Series Furnace issues

[stinger608]

So, have a 2019 Jayco JayFeather 27RL with the Dometic DF Series LP gas furnace.

Took it out for the first time this season and it was pretty cool in the evening and nights.

Turned on the furnace and it worked perfect for the first night.

Woke up yesterday morning and it was only about 50 degrees in the trailer.

Furnace wouldn't lite or come on at all. Has this thermostat installed:
https://www.amazon.com/Dometic-Air-C...NsaWNrPXRydWU=

Turned the thermostat off and let it sit for a minute or so. Turned it back on and put to heat then set the temp to 70 degrees.

Few seconds later the fan started as normal. However it only ran for about a minute or so and just shut down.

Did this same process 3 or 4 times and now the furnace doesn't seem like it's even calling for heat. Just starts the fan, as normal, but I don't hear any type of ignition.

Not sure if it's the thermostat or possibly the sail switch.

If you see this Old-Biscuit, I'd appreciate your input man.

[Old-Biscuit]

DC to circuit board......

When fan comes up to speed the airflow closes the Sail Switch which allows DC to Limit Switch (which is always closed) then to Circuit Board
When circuit board receive that DC it then sends DC to Spark Electrode/Gas Valve for ignition

You have DC to furnace/DC to/from thermostat cause Fan starts

Furnace NOT lighting off could be Sail Switch/Limit Switch Circuit
OR
Could be 'BLW' circuit on the circuit board (not restarting unless you turn T-stat off back on)


On the Circuit Board is a 4 wire connector
Black.....DC grd from Fan Motor
Red.......DC + to gas valve
Blue......DC + from T-stat/to input side of Sail Switch/Circuit Board
Blue.....DC+ completed circuit thru sail switch/limit switch to circuit board
**That Blue wire (top position) is the one that signals circuit board for ignition (Must have DC+ when sail switch closes)

[Old-Biscuit]

Wiring Diagram

[stinger608]

Thanks so much for the info Old-Biscuit!!!!!!!!!

Do I have to pull the furnace to inspect/test the sail switch and limit switch?

Or can I take the outer panel (inside trailer, not exhaust port)?

I can remove to inside trim and get to the furnace but I am wondering about the 2 questions above.

Again, thank you so much bud.

[Old-Biscuit]

If you do not have the External Access Panel...just the intake/exhaust port then you will need to pull furnace from cabinet

See pgs 16, 17, 18 for the 3 installation options
https://www.dometic.com/assets/14/52...1_01_81452.pdf

[stinger608]

Yeah, looking at the Dometic design, the blower assembly is kind of by the exhaust port and I see why the furnace will need pulled.

Not a huge biggie as we have time before we are heading up in the mountains where the nights get down in the 30's and low 40's

Thanks so much Old-Biscuit for all the info sir.

[Old-Biscuit]

Never understood why ALL RV Furnaces do not have exterior access panels

So much easier to work on them!!!

[stinger608]

Originally Posted by Old-Biscuit

Never understood why ALL RV Furnaces do not have exterior access panels

So much easier to work on them!!!

Yeah, no kidding!!!!

[Skip426]

Originally Posted by Old-Biscuit

Never understood why ALL RV Furnaces do not have exterior access panels

So much easier to work on them!!!

It would be nice if the designer/engineers , had to repair their products for a year before they were released to the public .

Case in point ... is this the best place to mount a starter ?

[Old-Biscuit]

Navy Ships were just as bad......had to disassemble/remove perfectly fine operating equipment to gain access for removal of broken equipment

[stinger608]

So, at least all of the ducts are just the 1/4 turn to remove.

That helps.

So, how long does it usually take to remove a furnace Old-Biscuit?

I'm figuring about an hour?

Suppose to turn cold and rainy the next few days, so will probably wait until this next weekend to pull it.

[Old-Biscuit]

Depends on workable space

Remove Intake/Exhaust tube
Disconnect ducts
Disconnect propane line....double wrench
Disconnect wiring...should be harness connector you pull apart
Remove mounting screws
Pull furnace from cabinet

Connect 12VDC and propane sources .......bench test
ID problem
Get parts/replace/bench test/reinstall

Figure 2 hours.......plan on 4 LOL

[stinger608]

Originally Posted by Old-Biscuit

Depends on workable space

Remove Intake/Exhaust tube
Disconnect ducts
Disconnect propane line....double wrench
Disconnect wiring...should be harness connector you pull apart
Remove mounting screws
Pull furnace from cabinet

Connect 12VDC and propane sources .......bench test
ID problem
Get parts/replace/bench test/reinstall

Figure 2 hours.......plan on 4 LOL

Yeah, that's about what I figured was 4 hours to get it pulled and try to bench test it.

Not sure what I'm going to use for the bench test. I do have a hose that came for external propane tank to use on a Blackstone that has an AN fitting.

Hopefully it's the correct size. If not, I should be able to find one at one of the local hydraulic shops.

Do I need to loop the 12VDC through some kind of switch, and, will I need to purchase a plug to adapt to the wiring coming out of the furnace?

[Old-Biscuit]

12VDC POS to RED wire
12VDC NEG to BLACK wire

Tie the 2 BLUES wires together (this will start the furnace)