I have a York Stellar 2000 combination A/C and gas furnace in one package. It sits on a concrete pad outside the house. Its about 12 years old. As a side comment, I would say these combo units are (or were then) definitely not designed for long term outdoor usage in the humid southeast... Either that or they were designed to conk out right at the end of the warranty period....
The unit will work for many hours cycling heat on and off as needed. Then at some really inconvenient time like 2:30AM, it gets into a state where all it will do is blow cold air. When it gets into this state, if I pull the fuse block and plug it back in to reset the unit, what I see is that the flue motor turns on, and then after about 15 seconds, I hear the relay click and the indoor blower fan turns on. It's like it skips past the rest of the ignition sequence. (Normal sequence is: flue motor on 15 sec, hot surface ignitor on 3 sec, gas valve on 3 sec, trial for ignition and flame sensed, then finally indoor blower on after 30 sec.)
According the the York installation instructions these are the diagnostic LED blink codes for the control PC board:
OFF - normal operation
ON - board failure
1 flash - ignition attempts or recycles
2 flashes - compressor low pressure switch open
3 flashes - compressor high pressure switch open
4 flashes - flue inducer cetrifugal switch open (fault) or closed (fault)
5 flashes - flame rollout switch open
6 flashes - furnace high limit switch open
7 flashes - (optional) heating mode 1 hour waiting period for auto reset from flame failure lockout
Now here's my problem. When the unit gets into this blowing only cold state, the LED is blinking 8 flashes. There is no 8 flashes on the list. Anyone have an idea what 8 means?
Then again, sometimes after reseting the unit with the fuse block it will start to work properly for another 4 - 6 - 10 hours. Sometimes a day or so.
The circuit board is a Robertshaw 100-825-04 which a Google search says is now obsolete so I can't find any documentation on it. Also it appears that Robertshaw is not even in the HVAC control board business any more.
Thanks and Happy Thanksgiving!