AirCon - not cold, but compressor working?

[more_fasterer]

I did some more tests on the aircon system today, to better understand where the fault lies (I hate not knowing these things!!). The behaviour now is consistently showing that it can't cool the car when revs are low (<1500rpm) or when it's asked to do a lot of cooling.

Here are the results, using INPA to get the relevant figures:

• Ambient temp 27c / 80f
• Interior temp 30c / 86f
• In the best-case scenario, i.e. 5min with revs held at 2000rpm and the interior fan at 20%, the evaporator temperature only got down to 21c / 70f
• If the car was left to idle, or I pressed the "MAX" button on the IHKA control panel, the evaporator rose to match the interior air temp.
• The pressure sensor voltage stayed very consistent throughout, 1.9V +/- 0.1V.
• The left heat exchanger sensor sat at 14c / 57f and only varied by a couple of degrees during the test.
• The right heat exchanger sensor ran at the same temperature as the evaporator throughout.
• Both solar sensors remained at 0V throughout the test, with bright sunshine the entire time.

So, a couple of questions from me:

• What do Ze Chermans mean when they use the term "left / right heat exchanger?" Are these the left & right heater cores?
• Are the solar sensors meant to be 0V? There are no errors logged

.

Given the pressure levels are in range, yet the pressure sensor barely budged throughout, I reckon this is leaning more and more towards the variable compressor being stuck in its minimum compression setting. I've got a professional turning up on Thursday, so I'll ultimately leave it up to him to sort unless he starts sounding fishy.