The Ac on in my 05 blows only hot air. My first thought was low R-134a. So I hooked a can and gauge up to my low Ac port. I have the car running and max Ac on but cannot get the R-134a to go into the low port. Is there a secret to doing it with mustangs? I have done this time and time again on other cars. Please help!

 

If it's hooked up right it should go right in. The only other thing I can think of is if there is too much pressure in there and preventing it from going in.. This could be a bad expansion or needle valve. Not sure what our cars come with in their AC system. Are you sure it's the low pressure port? How do you know it needs refrigerant? Did you put a set of gauges on her? They really can be a great tool for diagnosing HVAC issues.