View Full Version : High pressure a/c sensor

08-15-2011, 11:53 PM
i got a 1998 firebird and just wondering how i can test the high pressure a/c sensor with out removing it from the line.

Also, can i bypass the sensor signal wire to the 5v or sensor ground to make the high speed fans engage?


08-17-2011, 02:15 AM
The high pressure switch turns applies the A/C compressor clutch when the pressure rises up to a certain point. To test it I would just turn your A/C on and see if the compressor clutch activates, you should easily hear the clutch kick on and off.

You can bypass the sensor by, I believe, just connecting the two wires. I'll have to look at the schematic again to make sure. However, I don't believe that this will give you the reaction you're looking for. Your fans go to high speed when your A/C kicks on, not when it turns off.

If you want I can look up the schematics and tell you how to wire a switch that will kick your fans on high manually. I believe you ground a wire but, like I said before, I'd have to look at the schematics again.

08-17-2011, 10:44 AM
Ok. I tried messing with the breakers and they work fine. I also hooked up a ground wire to the 87 and 30 (or something like that) parts of the breaker and it triggered the left/right fan to kick on "high" But it only runs on high until i unplug it, even when the car is off.. Maybe do I have bad wiring? Because, I bought the car a year ago with a used compressor that leaked. Im not sure if the guy that replaced the old one knew what he was doing. So I bought a new compressor and replaced it my self but, I dont know if the wirng is messed up.

Also the clutch "clicks" but compressor but they still wont kick on high..

08-17-2011, 04:43 PM
Maybe the fans don't go on high when the A/C is on, maybe they just click on. Either way, it sounds like they are working fine. Unless, you're engine is getting hot, your A/C is on and your fans are still on low.

Your description of grounding the relay and still having your fans on when your car is off is how it would run. The relay is hot at all times and the PCM grounds the relay to activate it.

If you want you can hook up a switch to ground and then connect the other terminal of the switch to the wire that you grounded to activate the fans at high speed. That way you just flip the switch from your driver's seat and your fans kick on high.

08-17-2011, 09:16 PM
Ok so I hooked up a switch to it and it works that way. But I did a lil more digging around and I found out that im not getting power to my relays for some reason. What do u think it could be

08-18-2011, 05:40 PM
Well, if you hooked up a switch like I said and it's working then your relays are getting power just fine.

08-22-2011, 11:32 PM
Its a transducer.........the pcm uses its output to control the ac compressor and fans and fuel mixture.....its not what you think. The ac conpressors on these cars DO NOT CYCLE! The compressor should run all the time, the compressor itself unloads. The transducer takes the pressure reading and sends it back to the pcm as a signal. Be careful what you mess with ubnless you like replacing the PCM and other expensive electronics. Go buy a factory manual before you really screw things up.