Whirlpool PACF212HP W portable air conditioner, upper fan only turns slowly.

[spleenharvester]

I just acquired this portable aircon, history unknown. Its behaviour is quite strange:

• When turned on and placed into cooling mode, the upper fan (cold air out) just spins slowly. The compressor and lower fan do not run.
• If the device is then placed into heating mode and then back into cooling mode, the lower fan and compressor kick in and start cooling, but the upper fan still only spins slowly.
• If the device is placed into fan-only mode, the upper fan does not respond to low/medium/high speed toggles - just keeps running slowly.
• Display and buttons all behave normally aside from the malfunction.

Here is what I've done so far:

• Replaced all the caps except the big filter cap (they were junk AiSHi caps). No change in behaviour.
• Checked +5V, +12V, +15V and +18V rails referenced to appropriate grounds - all within range
• Noted the middle opto is not activated. If injecting 1.2V into pin 1 of the opto the upper fan motor makes a revving noise but the fan doesn't actually increase in speed
• Measured the upper fan voltage outputs - VDC = 330V, 15V = 15V, FG ~ 10V, VSP ~ 3V - regardless of whether the speed toggle is set to low, medium or high

Drawing a blank with this to be honest, I have been tracing the whole board trying to find any readings that correlate with the low/medium/high speed toggle but can't seem to find one. I am starting to think the main control IC is hosed but I haven't had any luck tracing the pins just yet, partly because I am having trouble removing the conformal coating. Pics attached - note the iffy looking solder around the optos is just from me lifting the legs etc, I had a good up-close look at the board before I started working on it and did not see any abnormalities. The main components include two SAP2003SC transistor arrays (one seems to control the small vent cover motor and the other controls the relays), a 48 pin unknown control IC, and an INN2063K flyback switcher.

Thanks

[spleenharvester]

Update - I've since disconnected VSP from the upper fan and injected voltage into it from a bench supply - it does respond to voltage increments so it appears to be a fault in how VSP is generated

Update 2 - the lack of VSP appears to be a GPIO fault, I've ruled out everything downstream of it. I can activate the fan by pulling BC807's base to ground through a 10K but it still doesn't seem to respond to low/med/high inputs and I can't figure out what is supposed to be generating them? Another dead GPIO pin perhaps?

[spleenharvester]

Final update, gave up trying to restore speed control and just installed a permanent 10K to logic level side ground from the base of the BC807 to keep the fan at maximum all the time (in this VSP system 3V = low, 5V = med and 7V = high). Machine now works perfectly aside from not responding to low/medium/high toggle