Auto Air Conditioning & Heater Repair: A/C in a 1997 Chevy S-10 Blazer, brake master cylinder, vacuum line

Question
I got a new AC compressor on my 1997 Chevy S-10 Blazer now I am having problems with the blower it works when it wants.  Sometimes when you turn the truck on and turn the AC on you can hear the AC compressor working but no fan not even on heat till you get on the freeway and get going then It will come back on slowly. Like the vents are stuck shut till air pushes them open. When it does starts blowing it comes out of the defroster at the windshield. I have to turn the switch to the floor then back to AC to get it to come out the front vents.  The faster I go (like getting on the freeway) it goes back to the defroster vents till I get up to speed then it slowly comes back to front vents but not all the way still some comes out the defroster vents.  Like I said before its like the door to the vents is stuck either closed or in the defrost position. Any clue what to do???

Answer
The main vacuum line from the engine that runs thru the firewall is broken or disconnected. Look HARD for this small black plastic vacuum line as it may be routed within the wiring harness and or located undetr the brake master cylinder.


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