230.6 (W114) A/C blower switch

[suiteR]

My 230.6 has air-cond, not sure if it's fitted at factory
The system brokedown. It started with this...
There are 4-notch to turn clockwise on the blower switch: 0-1-2-3 (max speed). The switch seemed not workin' on "2", therefore it had only slow or fast speed blowing. It worked fine for the past year. One day, when turning the knob, no cool air blowing out , but heard the A/C compressor clutch still engaged. I didn't use the system for a while, then the compressor clutch no long engaged.

So, my first attemp was to remove everything and try to reach the blower switch. The switch seems complicated (to me). I tried cleaning contact, plugs/sockets with WD40, won't work at all. The blower switch end seems not easy to be removed!?
I even loosened the centre console, just in case need to check the thermostat dial (but don't know what to do w/ it )

I tried to directly wire 12V to the compressor clutch, it works. Now, I have no clue where I should check further to make the system work again.

Please advise further diagnosis.

THANKS in advance!