Mazda Repair: 1996 Mazda Protege AC works until engine is warmed up, vacuum test, startup period

Question
The AC on my 1996 Protege work will work normally for about 10 to 15 minutes.  At that point it will start blowing only warm air.  I have check the charge with a kit from Walmart and have added less than a can of R-134a.  This has only made the air colder during that startup period.  I have also clean the throttle body with some STP Throttle Body cleaner.  This has made the engine rpm respond more to when the AC is turned on.  After the engine is warmed up, the rpms will increase/decrease as I turn the AC on and off.  The rpms will then stablize at around 700.  So the engine is acting like the AC is on.  When starting up, the fat tube at the front of the engine will get cold until the engine warms up.  Then the AC starts blowing warm air and that tube gets, and stays, warm.The AC on my 1996 Protege work will work normally for about 10 to 15 minutes.  At that point it will start blowing only warm air.  I have check the charge with a kit from Walmart and have added less than a can of R-134a.  This has only made the air colder during that startup period.  I have also clean the throttle body with some STP Throttle Body cleaner.  This has made the engine rpm respond more to when the AC is turned on.  After the engine is warmed up, the rpms will increase/decrease as I turn the AC on and off.  The rpms will then stablize at around 700.  So the engine is acting like the AC is on.  When starting up, the fat tube at the front of the engine will get cold until the engine warms up.  Then the AC starts blowing warm air and that tube gets, and stays, warm.  If I let the car cool down and then restart it, the AC will work again until the engine has warmed up again.

Answer
Sounds like you need to see a certified AC shop. They will be able to pressure test and vacuum test the system to determine the exact reason why you cannot build the proper pressure in your system for more than 15 min at a time. Long distance diagnosis will not help in this case, but you can be sure that the wall mart kit will not do you any favors with this problem as it may require a new compressor and will defiantly require a full system recharge that the little cans cannot supply.

Good luck and keep me informed on any other details that arise.


Regards,


John