Electric clutch fan running high all the time , Car overheating with A/C on

I have a 2002 Chevy trailblazer . My car was idling
with A/C on for about 5 minutes on a hot day ( 15
yr old son was in the car) .When I came back to the
car I could see steam coming from the front .
Turned off the engine , pooped the hood and the
top plastic piece of radiator was cracked !!   
Coolant was leaking out of crack along with steam.
Funny thing is I had only had this car about 2
weeks before that happened . In the two weeks
driving it  No SES lights came on ,  and  temp had
always ran steady at 210. The only thing that
happened was right after I bought the car  the A /C
ran a little warm one morning . I turned it off gave it
a break and then like magic the cool air was back  .

Fastforward to present time. I have replaced the
busted radiator , water pump , electric fan clutch , &
thermostat . Now after all that the code P0526 is
popping up.  The radiator fan ( or electric fan
clutch )  runs at high speed all the time even when
the car is idling . The temp gauge stays steady at
210 UNLESS the A/C is on and I hit stop and go
traffic.  When this occurs I have to pull over and
turn off the car . Its hot were I live and I have little
ones . I REALLY need my air conditioner.

Also, I noticed this morning on the highway It feels
like Im pulling a boat or something.  I can hear the
electri fan and its really loud like an airplane sound
.  I dont know what else to do to fix this problem .
Any ideas ?  Is there a temp sensor that needs to
be replaced ? Or should I try a new coolant fan
harness ? Help please !