Seemingly poor A/C efficiency in Chrysler Town & Country

Question

I feel like the A/C in my 2012 Chrysler Town & Country is under-performing. So, I measured the A/C temperature output on it and my 2003 Toyota Corolla, and I'm having trouble reconciling the results.

Here are the experimental results, based on this setup:

Vehicle        | Outside Condition | Temp Setting   | Fan Setting    | Measured Output Temp
===============|===================|================|================|=====================
Town & Country | 85°F / 55% rh     | Coldest - "LO" | Min ("1" bar)  | 42°F
                                   | Coldest - "LO" | Max ("6" bar)  | 60°F
---------------|-------------------|----------------|----------------|---------------------
Corolla        | 94°F / 35% rh     | Coldest        | Min ("1")      | 45°F
                                   | Coldest        | Max ("4")      | 49°F

(These results show that as the blower speed increases so does the output temperature. This Q&A explains why in lay terms, or see also this technical summary. For a general guide on auto A/C implementation, see this article.)

But why does the Toyota increase 4°F, while the Town & Country increases 18°F? I'd expect a significantly newer vehicle to have the same or better A/C output performance. But no: in the Toyota, one tick more on the blower is one degree up in temperature. In the Chrysler, one blower tick up is four degrees up.

That doesn't make sense to me. Is the A/C on the Chrysler under-performing, and I should spend the cash to have a pro look at it: or is this all just about perception, and I should be happy with it?

---

Update: Indeed, the A/C was under-performing. The low pressure side was at 20 psi, where nominally it should be around 30 psi. I took it to a pro, who found a failed thermal exhaust valve. Replaced the valve and recharge recycled the refrigerant. Now it blows 48°F at coldest with the blower on maximum. This is inline with the performance from the Corolla.

Answer 1

I already commented on an answer to your other question: https://mechanics.stackexchange.com/a/31965/6794

The bottomline is: There's no sense in trying to compare A/C systems in different vehicle types.

If a workshop is out for a quick buck, they will happily evacuate and refill your A/C refrigerant, whether it's needed or not. (I regularly hear the sales persons bluntly lying to customers stating that "the manufacturer recommends this procedure once every two years", while I know that (most?) manufacturers explicitly claim their systems are "maintenance-free".)

Most manufacturers define the A/C as fully functional as long as it maintains low temperatures (<10°C) at the vents on low fan and something like 1500-2000rpm. And it also makes sense this way: A/Cs are controlled via a kind of thermostat which maintains about 0-5°C at the evaporator. If small amounts of refrigerant are lost the thermostat will compensate for that. Only when the refrigerant level is so low that the thermostat cannot maintain those temperatures action is needed; and that's exactly when the air at the vent does not reach those low temperatures mentioned above anymore.

Have an A/C service done as @vini_i suggested for your peace of mind if you want. You may or may not notice an increase in cooling-power afterwards. Judging from your measurements, service is not necessary yet though.

Maybe also note that the A/C system is automatically turned off if a dangerously low level (pressure) of refrigerant is sensed, so that no permanent damage will occur. If that ever happens, you will have no cooling effect anymore and should definitely have the A/C serviced soon.