Atwood Furnace Problem. Help?
Have an Atwood Model 7920-ll in our 2000 Lance 1010. Other day we were in Northern NH and it got a little chilly in the evening. We turned on the furnace before bed and it was blowing nice hot air. ...
Forum Discussion
How the furnace works (Well steps in operation)
1: Thermostat calls for heat
2: Control board starts blower (This is happening)
3: Sail switch closes (It appears this is happening too, the sail switch is closed by the movement of air across a plastic paddle or "Sail" it is inside the furnace).
4: Control board opens gas valve and begins ignitiion sequience (Starts making sparks) you said you heard the sparks.. Did gas flow.. See note 1 below
5: Burner ignights (you said this did not happen)
6: Thermocouple heats up
7: Control board either senses .480 volt (480 mV) from thermocouple.. .or not
8a: If it does operation continues till T-Stat says "Hot enough"
8b: if it does not it tries agin, usually 3 times, then locks out.
9 Burner shuts off
10 Blower shuts off.
Note 1: for gas to flow you need gas to flow, the valve must be open, if your propane (Explosive gas) Detector operates an emergency cut off solenoid it must be on and functioning properly.. The solenoid on the furnace must be functioning properly and finally.. There is an insect that likes to nest in the burner orifice completly blocking it so gas can not flow (or other debris).
On my furnace the burner did light, i could hear it light, and the thermocouple made with the .480 (I tested it) but the control board.. Failed to detect it
This can be due to a bad connection but that was not my problem (I made sure of it)
It can also be due to a bad control board
OEM board, roughly 250 at the time
Dinosaur boards "Generic" repalcement, 108 INCLUDING S&H, And it's a better board. Very well built in the USA board. Better design too.
I do not, however, think the control board is your problem.
1: Thermostat calls for heat
2: Control board starts blower (This is happening)
3: Sail switch closes (It appears this is happening too, the sail switch is closed by the movement of air across a plastic paddle or "Sail" it is inside the furnace).
4: Control board opens gas valve and begins ignitiion sequience (Starts making sparks) you said you heard the sparks.. Did gas flow.. See note 1 below
5: Burner ignights (you said this did not happen)
6: Thermocouple heats up
7: Control board either senses .480 volt (480 mV) from thermocouple.. .or not
8a: If it does operation continues till T-Stat says "Hot enough"
8b: if it does not it tries agin, usually 3 times, then locks out.
9 Burner shuts off
10 Blower shuts off.
Note 1: for gas to flow you need gas to flow, the valve must be open, if your propane (Explosive gas) Detector operates an emergency cut off solenoid it must be on and functioning properly.. The solenoid on the furnace must be functioning properly and finally.. There is an insect that likes to nest in the burner orifice completly blocking it so gas can not flow (or other debris).
On my furnace the burner did light, i could hear it light, and the thermocouple made with the .480 (I tested it) but the control board.. Failed to detect it
This can be due to a bad connection but that was not my problem (I made sure of it)
It can also be due to a bad control board
OEM board, roughly 250 at the time
Dinosaur boards "Generic" repalcement, 108 INCLUDING S&H, And it's a better board. Very well built in the USA board. Better design too.
I do not, however, think the control board is your problem.
