I think freon is alittle low. How much should high and low side pressures be? What conditions are required for testing? Should I add oil if I need to add freon? By the way I have a 2000FRC. Thanks for your help guys any info is appreciated.

 

The guy that charged mine recently said 50/250 - I believe most freon has oil already mixed in -

 

Unless it is really low, you can't tell the freon charge from the pressures. The best way to charge it is to discharge it completely and then add the specified amount. The whole thing is a bit tricky since you can overcharge it and it won't work properly then either. And you have to worry about the amount of oil in the system. Good luck

 

If you think you are low on freon, you can test that by taking the low side pressure with a gauge you can buy at any parts house for under $10. If the gauge shows less than 25 psi, you need a charge. A charged system should show between 25 and 45 psi on the guage. Over 45 psi and it is overcharged.

 

Your AC system is very complex and requires all the above mentioned statements to be used with caution. Though most are correct, you have to understand the theory on how the system operates. You can NOT measure the system pressure without the system being operated. Just because you have the AC switch "ON" does NOT mean that the compressor is operating.

Ther are many combinations of Ambient air temps, humidity and Eng RPM that effect the high and low side pressures

The hotter it is out and the more LOAD you have on the system will cause the HIGH and LOW side to vary in pressure. There is a page and a half chart that gives pressures that vary with all of the above variables.

It is safe to assume that an older C5 will loose some FREON due to normal leakage. I have a 98 Coupe and the AC system still operates like new. If you have a C5 out of warranty and the AC system is not operating properly, it is possible it is low on feron. There are a multitude of other things that could be wrong also.

Here is s good example of what you should read under one set of conditions. If you have an outside air temp of 80 deg, your eng RPM is 1000 and the humidity is 80%; your low side (suction pressure should be 25 psi. Your high side should be 155 and the center vent temp should be 40 deg F.

I hope this helps.

Bill

 

so if I evac and recharge I have to add a given amount of oil?

 

I would buy an oil charge which contains about 1 oz of oil. If you see no visable signs of oil / freon leakage, you probably haven't leaked much. You probably don't need to add oil if there is no leakage you can see. You can check the drain from the evap. to see if there is oil. If there is you would need a new evap, and oil to go with it. Now back to the freon. Most systems with the low pressure cycle switch will cut off below 28 psi. So I charge most systems up to about 30 psi on the suction side and I look for 230 to 250 PSI on the high side. (Granted this varies a small amount with outside air temp. I normally don't add freon under 80 F.) You really don't need to evacuate to add freon to make up for minor system leakage.

What is important is to purge all the air out of the lines to the gauge prior to sending freon through to the system. You do this by hooking up the gauges to a freon supply and allow a small amount to purge through the valve to the hose connection. Do this with both valves on the gauge set open. Then close both gauges and make the hook up.
Good luck.. 99 Nassau Blue