The air conditioning in my DII is not performing well this summer. I checked the low-side pressure using the little gauge included with the A/C recharge kit I bought nearly six years ago. I was surprised that it showed the system overcharged, at about 54 psi instead of the 15-45 psi that’s apparently the target range.

I was really surprised to find that the system was overcharged. It has performed pretty well the last six years since I last recharged it and I gotta believe that when I did recharge it I kept it within spec.

I used a darkroom stem thermometer to check the temperature of the air coming out of the vents. The lowest temperature I observed was about 50 degrees, compared to temps in the mid-30s I get with my other car.

So what should I do next? Would too much refrigerant in the system cause it to underperform? Should I try just venting some of the refrigerant to the atmosphere to get the pressure down? (Egad!!!) Or, after 16 years does the receiver/drier need to be replaced even though the system has never been opened? What do y’all think? Thanks.

 

Over charge can kill a A/C system. If it were mine, i would lower the pressure to it proper range and see it that makes a difference. If it doesn't. you should use a 2 gauge set of gauges and see exactly what is going on or find shop that specializes in a/c systems to test it properly.
Let us know what you find.

 

It's hard to tell what's going on without being able to see the high side pressure too. It could be a weak compressor, especially on the suction side causing higher than normal low side pressures. You'd probably be able to see this as lower than normal high side pressures. An expansion valves this is just SLIGHTLY stuck open might also cause pressures to not suck down on the low side. When the system is off and sitting for a while, pressure equalize on both sides, and you could end up with over 80 or 100 on both sides. So seeing a high number on the lower side doesn't always mean there is too much refrigerant.

 

are you sure the compressor was engaged when you checked the preasure, it not it will read high.

 

Keep in mind also, that the heater core is next to the airconditioning evaporator, and if there is a failed air diverter/gate/handler, one will fight the other with unexplainable underperforming behavior and pressure readings.

The selection of recirculation or not also changes performance.

 

+1 on this. Be sure the a/c system is on and set to the coldest setting with engine running of course. And make sure the a/c compressor clutch is engaged.

 

It the clutch is not engaged the system equalizes so you would get a wrong reading

 

Overcharge - the compressor will shut down from over pressure.
You will not get max cooling.

If there is air or moisture in the system - you'll also get bad performance.

You would need to pull a 25 BAR vacuum and get everything out of the system.
Then add freon and oil to it to make it perfect.

I would just bleed off some freon and put a thermometer on the vent.

With the fan on low and the A/C max = thinking 50 degrees would be reasonable.

When humid you should get icing on the low side out of the compressor.

 

I believe jfall ment to say 28 psi, 25 bar would be about 350psi.