Atwood Furnace Death and Resurection

[Boomer485]

Last year, and part of this year I was in Minnesota into February. My Sunny did a marvelous job of keeping me warm and cozy. Around the first of the year my furnace gave up the ghost. The motor died. Horribly. There were times I was afraid it was going to simply jump out into the snow.



What to do? I found a good temporary solution. A local box lumberyard store (Menards) had a very nice 1500 Watt space heater! Saved the day. Sunny remained quite comfortable and snug.



Before I headed south and put her away for winter storage I ordered the parts needed to rebuild the unit.



First thing this year after taking her out of storage was to rebuild the furnace. I replaced the motor with a new assembly that had both blowers on it. However, to really do this I had to remove the entire thing from the trailer. Lots of tiny little screws holding it in.



Once I had the box out it was pretty simple. I removed the 9 screws holding the motor in. There is like a small wall that has three screws on top, three on the back, and three on the bottom.



Since I had everything apart I replaced the igniter and flame parts. Also the "wind" switch and the sensor in the heat exchange.



The really fun part was trying to get all the tiny screws back in, aligning so the holes were aligned. I used an Ice Pick/Scribe and a magnetized socket and managed to get them all back in. There were about 5 that I had to replace with a slightly larger screw to do the job.



Then the wiring. It should have been simple, and after a while it was. I had to remove the cover as I forgot about the blue and white wire on the wind switch. Then I had this mysterious black ground wire from the motor. Once I figured out where to plug that in on the ground with two other wires it was easy peasy. I did neaten everything up with wire wraps. Then came the big moment. I turned it on. Worked perfectly! Dam I was surprised. Also pleased.

[j52wf]

That blue wire with the blue plastic fitting on it is the one I have to play with when my furnace doesn't turn on. What is it for?

[Boomer485]

The blue wire seems to either go to the sail switch (which must detect movement to work) or to the ignition control board (left side of furnace with wires in plug). If the sail switch is bad, then you will have to futz with the wire to try and fool it. The model number of the furnace will tell you the most. There is a wiring diagram on the web site that will show you which wire goes where by model number. Check your connections for corrosion or bad crimp, that may help as well. If you cant fiind the manual with the wiring diagrams in it, let me know and I will send you the PDF file. Good luck.

[JohnB]

Great job Boomer! You done good.

Now you know how your furnace works from the inside out. It comes in handy every now and then.

Thanks for sharing. Good pics too.

John

[JohnB]

Originally Posted by j52wf

That blue wire with the blue plastic fitting on it is the one I have to play with when my furnace doesn't turn on. What is it for?

Hi Jim,

If this is the blue wire connection in the pic below, the one at the circuit breaker you are wiggling to get the furnace to work, that sounds like corrosion on the terminal. Clean up the connection.



Atwood uses blue differently pending the vintage and model of the furnace. Your 2007 camper should have the newest model at the time. Need to know the model number to be sure, but that blue wire supplies power to the furnace T stat run signal up in the roof AC unit and it supplies power to the furnace PC board. Blue then returns from the T stat run signal in the AC unit and starts the power being supplied to the furnace safety circuit (the sail switch and the over temp switch). Once power comes out of the sail switch, the wire turns white goes to the hi temp limit switch and then to the PC board.

Basically, that blue wire in the pic is the 12 VDC power that starts the whole furnace running after power left the circuit breaker. If you are wiggling it and it starts to work, then power is not getting out of the circuit breaker. The red wire on the circuit breaker is 12 VDC power to the breaker from the local on/off switch at the furnace which is fed by the camper fuse panel. If you have corrosion on one of them, the red on the circuit breaker is suspect too. Check and clean up all of them.

Hope this helps

John