The 2001 Jag S Type is a 4L, left hand drive. The exterior temp registered 74deg F and the air from the registers starting at the driver door and moving to the passenger door is 69, 72, 79, 80 deg F with the AC set to LO and on recirculate.
I have replaced the heater control valve. No Improvement. I checked the old heater control valve and it was good. Checked the AC system and the low pressure side reads 25 psi and the high pressure side reads 150 psi with an ambient of 70 deg F. On startup I hear a sound like one of the stepper motors…it sounds like it is coming from the center of the dash. Also with the AC on and the fan in low position I can hear a strange noise…hard to describe.
I would appreciate some help to solve this problem. Today was a cool day but it has been in the mid to high 80s and the forecast is for some high 80s later this week.
Thanks for any suggestions/help

 

Pressures at 70 deg should be 35-40 and 145-160 your low low side could indicate moisture in the system.

 

Norri, Thank you for your response. The AC system has never been opened up. Is it possible to get moisture into the system under this condition?

 

17 years on original charge is a very good run, but these systems are only 99.99% sealed and over long time that 0.01% leads to various issues.

You will likely be able to fix this with a new dryer and top-off. I also think changing compressor oil is warranted on a system of this age, but not certain if it is problematic spot for S-type.

 

SinF, Thank you for this info. Do you think I need to evacuate the system to add a new Dryer?

 

Dryer removes moisture and is in-line with the system, so yes you have to depressurize the system to swap it. However, doing so is not a risk-free. Main concern is that shop recycles refrigerant without notifying you. Common problems are overfilling compressor oil, using contaminated refrigerant, and over-pressurizing.

If you can live with your existing system I'd leave it be.

Also, consider doing radiator fin cleaning (there is a tool for that) on condenser, replacing cabin filter, and ensuring your aux fan is working before you open up the system. Your problems could be as trivial as bug residue reducing effectivness of your condenser (it is located in front of radiator). Don't attempt to use high pressure wash on it yourself, I heard of bad outcomes.

 

SinF and Norri. Thanks for you advice. Based on you suggestions, I decided to top off the system. Added enough R134a to bring the low side pressure up to 35 psi. It now blows cold air on an 80 deg F sunny day.

 

What was the high side pressure just for info?

 

I was mainly interested in bringing the low pressure side up to 35 psi. I did check the high pressure side to determine if it was within the specs for the chart I was using. As I recall the high pressure side was around 170 to 180 psi.