HVAC troubleshooting- I've tried everything!
Going to do my best to explain this with my limited mechanical knowledge. I have a 2011 LX sedan. The AC had been acting a bit odd a few months ago in the summer in AZ. It would blow warm to hot air after awhile and the air compressor wouldn't always kick on. I did the test on Youtube where you unplug the sensor in one of the lines while the compressor is running- that tells you if the signal to kick the compressor on and off is broken. Well I unplugged whatever it was and the compressor did not stop, so I determined it was the control unit. The video on youtube explained that it was freezing over and no freon was moving.
A couple months later and I didn't need the AC anymore, but then the blower motor started acting up. I forget what problems were exactly occurring, but I determined it was either the blower motor itself or the resistor. I replaced the motor at first. It still would not blow or very intermittently. Fine, I replaced the resistor. It worked for awhile, but then only worked on high speeds. I found a cheaper motor and swapped it out, testing it before I replaced it. It worked on all speeds. A few days later, that now stopped working. I thought the resistor was bad, so put the original one back. It worked again for a few days and then the system stopped again.
FINALLY I thought I knew it had to be the HVAC control unit! So I went to the junk yard and pulled one out of a 2010 civic. Replaced it. STILL NOTHING. That is with the 2nd motor and the factory original resistor.
I did the self-diagnostic mode and it came up with 4 blinks which indicates problems with the mode control motor. At some point in all of this, I got it to show 6 blinks which indicates problem in the blower motor circuit.
What do I do next?? I am leaning towards a new resistor again in case the first was faulty but that doesn't explain why the fans don't kick on when the car is on accessory mode. It all seemed to point to the control unit!! What are the chances that one from the pick a part is bad? Any help is appreciated. Thank you!!