Quote:
Originally Posted by ATCguy
Ok guys, help me out here...
Am back in NC, living in my rig while continuing to recover from my spinal surgery. With this latest cold front, temps are now routinely falling below freezing at night.
The issue is the furnace is not coming on when the inside temp dips below the thermostat setting. The 20amp fuse is good. I can go outside, remove the cover, and I see the fault code light blinking once every 3 seconds. No apparent mechanical issues. I can manipulate the blower fan fins with my fingers... bang the side of the blower motor with my hand, cylcle the "reset button" off-on... and the blower motor starts up, the igniter lights, and it runs normally. The temps rise inside the rig, and all is ok... until the temp falls below the thermostat setting again, and the furnace fails to operate again until I go back outside again and go thru the same thing.
This has happened 2 nights in a row... and I'd like for it to not be 3 or 4. Any suggestions?
I know I've seen something similar to this discussed before... but after searching 6 pages thru this forum, can't find it.
I'd like to try rectifying this myself, but I'm limited by what I can do. I still don't have a working use of my right arm, so I'm not sure tearing the unit apart is an option. That said, I can get some help, if needed.
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FURNACE OPERATION OVERVIEW
This is generic description of RV furnace operation and applies to most DSI type furnaces.
1. The Thermostat calls for heat, sending DC current to the furnace.
2. A Time Delay Relay is energized and passes battery DC power to the blower motor.
3. The blower motor and fans spin, pulling air from the Air Return and generating a stream
of air through the Heat Exchanger and out the Ducts. At the same time another fan pulls
air from the Combustion Air Intake into the Combustion Chamber and out the Exhaust.
4. The fan air stream causes the Sail switch to close as the blower gets near full speed.
5. Power flows to the High Limit Switch and onward to the Control Circuit Board.
6. The Control Circuit Board opens the gas valve and generates a spark at the DSI Igniter.
7. The Burner ignites, building heat in the Combustion Chamber.
8. Heat passes through the Heat Exchanger, warming the air circulating through the Ducts.
9. The Thermostat reaches the Set Temperature and opens.
10. Power is removed from the Control Board and the Burner shuts down.
11. The fan continues to run to cool the furnace, until the Time Delay Relay opens again.
Pay particular attention to item #2. Your furnace operates as it should AFTER the the blower motor starts, in your case the second method of operation isn't happening, therefore rendering the thing inoperable.
Perhaps with the banging on the furnace the relay makes contact and the operation continues. I'd start with the relay.