2000 blazer lt in trouble with hvac

[Serge PETIT]

My 2000 4x4 , 4,3l , 4 doors , Automatic Blazer has trouble with the automatic AC .
Even when AC is switched off the compressor keep engaged and continue to produce cool air .
It seems that the compressor clutch is always engaged ( not noise of the clutch engaging and disengaging .
The accumulator is icy and no leak on the passenger floor
I have controled the fuses and they look good .
What can it be ?
Not enough gas in the system ?
The relay which stay sticked ?
Thanks in advance for your ideas because it's not here in France that I will get some !

[Airjer_]

What happens if you unplug the compressor?

[Serge PETIT]

When I unplug the coil of the clutch it disengaged .
I am just back from my parking lot where I have made the tests .
Results are :
1) low pressure sensor disconnected ..........Clutch engaged and compressor running
2) high pressure sensor disconnected...........Clutch engaged and compressor running
3) HVAC relay in the engine compartement fuse case pulled out ........clutch disconnected and compressor off
4) Clutch coil disconnected ......................clutch not engaged and compressor off
5) Automatic Climate Control module on the dash:
- AC switch off (no light) clutch engaged and compressor on
- ACswitch on (light on) clutch engaged and compressor on
I think we may consider that the compressor clutch is fonctioning right .

All fuses for A/C are OK .
I have checked the automatic AC control module connector......nothing special or disconnected

I think that now I have to check the "freon" in the circuit because I am surprised by the fact that the dry/evaporator is covered with frost in one minute !
If "freon" is normal I think that I will have to change the HVAC control module because a componant may have failed (?) even if ventilation , defrost, air recycling and all contactors positions are fonctionning .........

At the moment it's not very hot in France (around 75 °F) and I have no long travel planed so I have disconnected the coil of the clutch and will reconnect if necessary .

Any new opinions/ suggestions ?

Thanks for for your help .

[Airjer_]

Manual or Automatic HVAC?

Before I spent anything I think I would at least look at some data with a scan tool. I would want to see if there is an a/c request in the PCM and if Automatic an a/c request from the HVAC control module.

[Serge PETIT]

Yes it is an automatic ACC .
The problem is to find somebody with a TECH2 for US Chevy trucks here in France ..................
After having checked all the points described above the guy in charge of maintaining my Blazer suggested to unplug the ACC module to see if the clutch stay engaged . He is considering that if it is the case the ACC controle module is giving a bad order to the clutch and is the faulty and otherwise that it's a case of wiring and short in it .
What is your opinion ?

[Airjer_]

You don't need a tech2. Any higher end scan tool will let you see the data you need to see. I'm sure OTC or Snap-on scanners are around?

[Serge PETIT]

Finaly I decid that I will drive the Blazer to a very competent automotive AC specialist in September (closed for vacation in August) .
So thanks for your good support and I will update you with what he will found and do with the hope it may help somebody else .