What are these AC pressures telling me?

[HawkeyeScott]

This is the wife's 2007 Chrysler Pacifica 4.0 with original AC system components. Seemed to cool rather poorly just as the summer began. It blew some cool air but it was definitely under performing. But, just in the last week or so, it seems to have improved on its own. It's not the coldest it's ever been, but it's not bad.

I put gauges on it today. It was 85 degrees out. At idle, the low side read about 19 and the high side ranged from about 240 to 255. Then, at about 2500 rpm, the high side would surge to 325 with the low side pretty much staying put.

Based on what I see online, the low side is a little low at idle and the high side is normal. But at higher RPMs, the low side remains low while the high side is very high. Again, though, the system is putting out a fair amount of cool air.

Blockage? Dying component? Investigate more? Leave it alone? Thanks.

 

[spasm3]

Does the fan work? Condenser clean ? 19 on the low side may be a bit undercharged.

 

[HawkeyeScott]

Yep, both fans are running and the condenser is clean.

 

[Chris142]

Has anyone added refrigerant?

 

[DNVDMAX]

Debris possibly blocking orifice tube or expansion valve.

 

[spasm3]

Originally Posted By: DNVDMAX
Debris possibly blocking orifice tube or expansion valve.


Good suggestion, especially if any " stop leak " has been added.

 

[CT8]

Originally Posted By: Chris142
Has anyone added refrigerant?
Chris is a A/C pro !! this.

 

[mk378]

If the suction line from the evaporator to the compressor is not cold, you have a blockage. I think this will be a TXV system and those valves can get stuck. If stop leak has been added of course all bets are off.

If the line is cold, the air inside the car should be cold too, if it is not the heater may be reheating it.

 

[i_hate_autofraud]

As noted above, put you hand on the exposed pipes near the compressor, the large one ('return' from the evaporator under the dash)
has to be cold.

The small dia pipe off the compressor must be warm/hot.

CHECK your air blend doors & actuators in the dash, they tend to be weak or sticky and won't fully
open to the cold a/c position.

 

[mk378]

Originally Posted By: i_hate_autofraud


The small dia pipe off the compressor must be warm/hot.


The discharge pipe is normally hot enough to burn you, and it only gets hotter if the refrigerant charge is low, so touching it isn't advisable. It won't tell you much.

 

[HawkeyeScott]

Initial plan was to add refrigerant but figured that would automatically send the high side pressures higher. Is that an incorrect assumption?

 

[mk378]

The high side being that high, with the fans running and ambient of 85, suggests that there is plenty of refrigerant.