Deepsea

Sorry for the delay, family issues and attention. It was mentioned in the string, "what was the number of times the red light flashed on the circuit board before I removed it." I was not able to see the light flash because I could not see the back of the furnace. During the troubleshooting phase all indications pointed to the circuit board which was replaced with a Dinosaur, and since I built a test bench for the furnace to easily trouble shoot and test the furnace. Now I wanted to answer the flashing red light question, I put the old circuit board in to see what the red light indicated. After installation of the old circuit board, the furnace fired right up and functioned as designed. Moving a head, we went camping last weekend, the first night I set the thermostat to heat and the A/C fan turned on then the furnace fired up. The A/C fan stated on and the furnace maintained the temperature through out the night. Second night same as above, but the furnace would not light. The trailer was hooked up to shore power with the electric water heater on. (Glad I had my back up oil heater.) Brought the trailer home, the following day on battery power, the furnace lit off with no A/C fan. A friend of mine strongly suggested I replace my dual propane regulator. This is so frustrating, I am ready to replace the furnace with a Espar Airtonic diesel heater. Of course I appreciate anyones input on this matter. Frank

Let me start off with saying THANK YOU for everyone's input on this frustrating issue. As everyone has thoroughly read my first post indicated my findings in detail and what I have tried or replace. However, Kirk did ask if my old board provided flash codes. I could not see the flash codes because the there is no access to the back of unit unless, I removed the whole unit. It was not until I figured out how to remove the unit to bench test it so I would have access to the back of the unit. At that time all indication pointed at the circuit board and replacing the OEM board with a Dinosaur. So getting back to Krik's question, I decided to install the original circuit board to see the flash codes and provide this information to Kirk. Upon installing the original circuit board and by passing the thermostat, the furnace fired up as normal and continued to function as designed. I removed the by-pass and try the thermostat controls. The unit continued to function. I fired up the furnace three more times prior to a full installation and totally button up, getting the same results. Again, this morning the furnace continues to function as designed. This leads me to believe the Dinosaur board has a malfunction but, I do not know what the cause of all this furnace issues was. I did make some improvements, such as the service bulletin that Kirk provided, installing a 7 sleeve also as I indicated in my original post, the circuit board was rubbing on the furnace housing, I secured the board with a couple of zip-ties to prevent any more chaffing. If all you guys saw this unit, and the parts removed and examined, this unit looks brand new, nothing worn out. I will report any other issues, good or bad and continue to hypothesize the possible issues of this simple furnace. Happy New Year's, Frank

The circuit board, as mentioned in my initial post is a new Dinosaur board that is visible in the video. I am not sure if the Dinosaur will flash the trouble codes like the OEM board. The probes are at factory specs, 1/8” apart and from the burner. I could bend the probes closer or father away from the burner to catch the flame....?

I published the video on YouTube https://youtu.be/6dTm5VV1nt8 Hopefully this may provide a more insight. Note that the board was re-located to prevent any rubbing as stated in my first post and now I am able to see the ignitor light turn off/on.

John and Vern, I appreciate your combined years of knowledge. I am curious what Kirk thoughts are. I will remove the board and check for clean connections. I attempted to post a video, but I could not get it down to the allowed file size.

I purchased a direct replacement High Limit Thermostat and installed the 7" sleeve as per service bulletin. However, I am still having the same problems as described in my first post. Please advise.

Wow! this is good information. I checked the high limit thermostat (HLT) with an Ohm meter, whited tested fine. However, like you stated, it may be shutting down at a lower temperature. I will replace the HLT and install a fiberglass sleeve as suggested in the service bulletin. Thank you for your help!

I have the following, Atwood AFMD30121 now (Dometic DFMD30121) Furnace Serial # 73299988, in an Eclipse Iconic 5th Wheel Model 2817CKG, two yeas old. The furnace will NOT stay lit. The furnace goes through the proving/ignition cycle. The Fan motor runs, the furnace fires up and I feel hot air through the vent for about 5 seconds, then the propane turns off. This process happens two more times, then goes through the purge cycle and locks out. I can turn (off and on) the reset to begin the above again with the same results. The two blue wires were twisted together to bypass the thermostat. The sail switch was checked, removed, cleaned (did not need cleaning) and checked with Ohm meter. The High Limit switched was Ohm, checked okay. Removed the original circuit board and noticed one of the "capacitor or resistors" had rubbed against the housing. I then replaced the circuit board with a NEW Dinosaur circuit board. A NEW Electrode was installed insuring 1/8” gap(s). The gas orifice was removed and cleaned; barley dirty. Gas valved was removed, energized and established an air flow. All exhaust, returns and air vents are clean and clear. The 5th Wheel is connected to shore power and batteries are at 13.5 volts. The hot water heater and stove work fine. The 5th Wheel is level. Both propane bottles are verified full. No pinched propane lines. Removed, inspected and clean “T” fitting in the propane line leading to furnace. I have Opened the propane bottles one at a time slowly, bled the propane lines to no avail. There is no access to the furnace from the outside. I remove the unit from inside of the trailer to gain access to the fan and control board side of the furnace. To remove unit, disconnect two power wires (- +) two blue wires from thermostat, disconnect four ducting, disconnect gas line and exhaust pipe. I brought the unit to the RV shop, they could not fix the unit. I called Dometic and they said it is out of warranty and they said cannot help. Can someone please help!