Auto Air Conditioning & Heater Repair: AC overcharged but not running, fuse box, puley

Question
Hello,
I recently tried to recharge the freon in my car, because it was only blowing hot air but as soon as I hooked the hose to the low side port the reading was sky high (150psi and over) I ran the ac on high for 15 minutes but the pressure didn't change. I tried this both in the day time when the outside temp was about 90 which is when my reading was about 175psi and in the dead of night when it was much cooler and the psi was 150. do you know what my problem might be or what I should check next?

thank you for your time
-John

Answer
John,
Was your compressor clutch engaged when you had the reading of 150psig? I don't believe it was. If it was not... this is normal, while the compressor is off the pressure in the lines equalize between the high and low sides. This is so the compressor doesn't have to fight against the high side head pressure when it is starting up. (kind of like starting a manual tranny car while it is in neutral rather than while it is in gear)
If it was engaged... then the valves inside your compressor are bleeding back through to each other terribly. That would require a compressor replacement. But again, I do not believe this to be the case. With your car on and your a/c running, if you look at your front plate on the compressor pulley, if it was engaged, it will be turning with the puley, if it is not engaed it will be stationary as the pulley turns.
As for why it would not be engaging...
being that I do not know what type of car we are talking about I cannot look up the wiring diagram for it, but the standard first checks are 1. Your fuses. You should have two fuses, one inside the cab fuse box that usually control the head unit, and one in the underhood box where your relays are that feeds power to your clutch itself. Check these first. If they are both good the next thing I would look at is your compressor clutch relay (underhood box) If your fuses are good, ths is usually the next step for power to get sent to your clutch. Check it for continuity across the appropriate terminals (again, I can't be more specific because I do not know the car) I believe that you will find one of these two components to be at fault. If not, send me more information and I will walk you through the wiring diagram as best I can.
 Thank you for the question, I hope I was of some assistance. If so, please remember to rate this answer. If I can do anything further during this process or in the future, do not hesitate to ask. Thank you again and good luck in everything.