Community Forums

Duster73 · 03-10-2022, 05:51 PM

So I picked up our new to us travel trailer today, when I get home I noticed the furnace blower was running. But no hot air was coming out.

I turned the thermostat to the off position just to verify and after 15 minutes the fan was still running. I tried different settings of auto, low and high. Nothing seemed to change, I then turn the thermostat heat all the way down to 40 and it still didn't shut off.

I reset the Dometic 3 button Thermostate and the fan still ran.

Once I pulled the furness fuse, the fan turned off. I waited a minute and reinstalled the fuse. The fan immediately came on.

Any ideas??

TandW · 03-10-2022, 07:53 PM

Stuck sail switch is all I can come up with. Bet the burner won't lite-off and produce heat.

Old-Biscuit · 03-10-2022, 08:07 PM

Only thing that will keep Furnace Fan Running is:
1) Failed TDR (Timed Delay Relay) used on older furnace controls
2) Failed BLW (Blower Circuit) on Circuit Board...replaced the TDR

12VDC+ from that Fused Source goes to TDR or Circuit Board.
When fail power to fan is ON continuously

Furnace Year/Brand/Model???

glwinger · 03-11-2022, 10:28 AM

Quote:

Originally Posted by TandW

Stuck sail switch is all I can come up with. Bet the burner won't lite-off and produce heat.

Sail switch does not control the fan. It tells the control board to fire the burner if sufficient air is flowing.

Likely a stuck fan relay or defective control board.

Old-Biscuit · 03-11-2022, 10:35 AM

Quote:

Originally Posted by glwinger

Sail switch does not control the fan. It tells the control board to fire the burner if sufficient air is flowing.

Likely a stuck fan relay or defective control board.

And if Sail Switch is stuck closed the circuit board senses that and will not allow any functions to occur

Bad TDR or Bad Circuit Board is only way for DC to get to Fan Motor and let it run continuously

Which one.....depends on Year/Brand/Model of Furnace

Duster73 · 03-11-2022, 11:10 AM

So I pulled the furnace cover and got the furnace #. Its afmd25111_a

After watching some Youtube videos, I decided to pull the circuit board this morning. This thing looks toast. I guess there is a known issue where the board lays in pooled water. The circuit board is rusted and has blue oxidation on it.

Dometic has a "relocation kit" that just keeps the board out of the water with a plastic spacer. I am on hold now to see what they can do.

I am assuming this is the issue. If I can figure out how to add photos I will!

Duster73 · 03-11-2022, 11:20 AM

Also, how in the world is water getting into these units. Its not just mine, but a semi common thing I guess. The foam seal looks to be in good condition.

Should I silicon the outside of the access door or something?? I dont want it to look goofy.

Old-Biscuit · 03-11-2022, 11:29 AM

afmd25111
Atwood Furnace Medium cabinet DC 25K Btu with door

YES.......laying in water, corroded, rusty........definitely needs replaced and 'relocated'
Plastic bracket that lifts one end up

Unfortunately they do not sell just the bracket but bracket/circuit board combo
*Dinosaur Electronics Circuit Board (FAN50 Plus) is a better quality board and make your own spacer

See Pg 5 for Installation Info
http://techsupport.pdxrvwholesale.co...m-Furnaces.pdf