A/C high pressure switch bad?

99GTP

MEMBER
1999 PONTIAC GRAND PRIX
3.8L
6 CYL
2WD
AUTOMATIC
177,000 MILES

Hello, I am the owner of the car listed above gtp. My A/C was working fine until today when I got in my car and turned my A/C on it blew hot and never got cooled until I started driving. But then I my check engine light came on and I read the code and it said my A/C high pressure switch is too low or too high voltage. I do know that this controls the amount of pressure to let in the compressor before shutting the clutch off. My question is, do I have to evacuate my Freon to replace the switch or does my model vehicle have a shut off when removed?

4 Replies

KEN L

MASTER CERTIFIED MECHANIC
47,643 POSTS

In most cases you will not need to discharge the system because there is a Schrader valve that control the refrigerant when the sensor is removed, but is this valve gets stuck or was forgotten in the manufacturing process it will leak out so chances are you will be okay. Here is the location of the sensor so you can change it out in the diagrams below. I have included both the high and low side sensors, so you don't get them mixed up. The high side is the second one. Check out the diagrams (below). Please let us know if you need anything else to get the problem fixed.

Images (Click to make bigger)