Hello.

99 C5 here. I have owned the car since 02. A/C has never been serviced. A/C started blowing warm last year. A few days ago I attempted to add refrigerant myself after reading a bunch of threads here, especially the "Ac 101" one. I rented a A/C manifold gauge set and picked up one can of r-134a. I added about 10 oz and the passenger side was cold but the center and drivers side was still warm. It was getting late so I decided to disconnect the manifold gauge set and ended up with a small leak from the low side schrader valve. I blipped it a few times but no improvement. Next day I had the evacuation done so I could replace the schrader and investigate further.

Yesterday I rented a vacuum pump in addition to the manifold gauge that I already had. I also picked up a new schrader valve, (3) 12 oz bottles of r-134a plus one bottle of dye with a quick charge adapter. I replaced the schrader and connected the vacuum pump to the charge line on the gauges. With the vacuum applied, I opened both the low and high side valves on the gauges. I let this run for about 45 mins or so. After this I closed the low and high valves on the gauges. I let this sit for about 45 mins or there was no noticeable of the vacuum on either side of the gauges.

I then proceeded to charge the system. I connected my first can of r-134a to the charge line and opened the valve on can to allow refrigerant to enter the service line. Since a vacuum was still present on the low and high sides there was no need to be concerned with air in those two lines. I did however bleed air from the service line by unscrewing the hose directly connected to the gauges for a second or so to remove air from that line. With the car still off, I opened the low side valve on the gauges. Once the flow started to slow down I went ahead and started the car. At this point the compressor turned on as there was enough refrigerant in the system to do so. Once the can was empty I turned off the car closed the low side on the gauges and then the valve on the low side service port.

I then proceeded to put in one charge of dye on the low side service port directly. With the car running, I put in "one shot" or 3 seconds of dye into the low side service port. My next step was to put in the second can of r-134a. With the car off, I connected the low side hose from the gauges back onto the port. Since I was worried about air in the line on the low side, I connected the vacuum pump back to the service line on the gauges. With a vacuum applied, I opened the low side valve on the gauges while leaving the low side valve on the service port closed. After a few seconds I closed the low side valve on the gauges and then disconnected the vacuum pump.

Now with air removed from the low side hose, I connected my second can of r-134a and proceeded to bleed the air from the yellow service line as I did before. Once this was complete, I started the car and proceeded to put in the whole second can of r-134a. The air from center was cold at this point. It was late and I decided to stop for the night.

This morning with the gauges still connected, there was a static pressure of about 75 psi on both the low and high sides with car engine at room temperature. The temperature today in Chicago is about 66 degrees with 90% humidity. I am working in a garage with both the side and service opened so maybe it is a few degrees warmer at most. I started the car and turned the A/C on to the lowest temperature setting, fan on high plus I had a thermometer in the center vent. Recirculation was on. After about 3 minutes I proceeded to check the pressures. At 1000 rpm, I read 28 psi and 235 psi on the low and high side respectively. I also checked at 2000 rpm and got about 26 psi and 265 psi on the low and high side respectively. The center vent temp was around 38 degrees or so.

I realize it is not an ideal day to check A/C performance but how do those pressures look?
Doesn't the high side seem excessive?

I am tempted to put in more refrigerant simply for the fact that there is no way I could have put 1.5 lbs or 24 ounces in especially after purging air from the yellow service for both of the cans. I would expect there to be about 2 - 4 oz lost during that step. The center temperature does seem cold though.

Any thoughts?

 

Static pressure sounds about right.High side pressure will be a little higher than normal due to the fact there is not much air moving over the condensor to lwer the pressure.I would drive it to see how it does before I put too much freon in the system.Not good on the compressor.

 

You should also check that the radiator is free if debris. Low flow through the condenser will result on high high-side pressure.

 

Will do. Thanks!

 

Also, for testing purposes, you can aim a garden hose at the condenser, this will bring the high side down and somewhat simulate highway driving.