The A/C on my 1996 Z28 appears to have plenty of pressure ~120 PSI (measured with a gauge that comes with the A/C Refill can). When I have someone turn the A/C on inside the car, the clutch doesn't or isn't engaging.

To start the A/C cycling, what is the leading factor that sets it off? What I mean is what power gets transferred to the A/C components? Is it just power from the A/C panel switch to activate the relay on the front driver fender and then send power to the connector on the compressor, or what else gets powered when you turn the **** on the switch to A/C max?

I need to find out if I can fix this otherwise some electrical shop is going to get the best of me.

Thanks!

 

First of all is the 120PSI on the Low side or the High side? If its the side where you plug into to put in R134(Low side) then you are WAY TO HIGH!!!!!!............If you overpressure your system then the clutch won't work because there is a pressure switch on the system that won't let it. The best thing to do is drain the low side down to about 45psi, and the high side should ready about 210 or so. Try that and see what happens. If you have air in your system then the best thing to do is drain the entire system and get someone to pull a vacuum on it so get all the air out and then refill it with R134.

 

The 120 is on the larger diameter AC line. This is the one that is most forward of the two. I checked the same line on a friend's 95 Z28 and it measured out ~110.

So is the starting point for all AC operations the green wire getting powered from the relay on the driver side upper fender?

From shoebox's link, it is where the black cap (next to the dipstick) is located:
http://shbox.com/1/refrigerant_sensor.jpg

 

unhook your battery for 15 min.resets everything .mine was doing the same till i reset it now all is fine

 

Going through the same thing right now, this is what I KNOW. If your low side is reading 120 without the clutch cycling that is normal. It is supposed to be somewhere between 32-45 depending on outside temp when the clutch is cycling. Your system primarily operates off of the sensor that threads into the high side line just above the passenger side strut tower under the hood. This sensor reads low and high pressure limits and sends them to the PCM. If it fails one time, whether the system pressure is low, high, or the sensor malfunctions, it will set a trouble code in the PCM and it will not cylce the compressor, even if the pressures return to normal. You first have to clear the codes out of the PCM before the compressor will even cycle at all. My advice would to be to put the car on a scanner and find out if there are codes set involving the A/C system. Keep in mind it will not light the check engine light and the only way you can tell if there are codes is with a scan tool. The code will then tell you if the system is low pressured or high. Start with this and let me know what you find.

 

When I first bought my car (with 59k miles) the AC quit working. I did all kinds of troubleshooting, and it turned out to be the connector on the clutch. Pull it off and check it with a voltmeter...see if you get 12v when the AC is on. I bent the prongs so they would make better contact, and it has worked great for the last 180k miles.