Normal evaporator temperature?

[yurtesen]

I checked the evaporator temperature and when all the flaps are closed and fan speed is lowest, it goes down to 6C (outside temp 20C). If I put fan speed to full and open all the flaps, it goes up to 12C. (car is idling). The compressor clutch is all the time engaged.


Can you tell what you see in your MK4 for the following values?



What is the outside temp?:
What pressure does your G65 read when system is static? (before you start engine)
What pressure does your G65 read when A/C is ON?
What is your evaporator temperature when A/C is ON fan blowing lowest speed?
What is your evaporator temperature when A/C is ON fan blowing full blast?

 

[yurtesen]

Well today morning I went into the car and check the static system pressure. The coolant temp sensor said 15C, ambient temp 15.5C and I expect refrigerant was similar temperature.
- G65 read 3.9bar - that is exactly what it should be according to workshop manual.

Then I started the engine and evaporator G263 temperature went down to exactly 5C

But the outside temperature was obviously ~15C so it is not a real test of power. I have turned on heating to max and enabled recirculation on to increase cabin temp, also turned off the A/C.
The evaporator temp climbed up to 32C. Then I engaged A/C again (while in recirc mode and max heat). The evaporator temp went down slowly to 5C again.
The highest G65 pressure reading was 10.3bar.

So, it seems to be going to 5C consistently. Now the question is if this is what others see in their vehicles?

That said 5C seems quite reasonable value. But it would have been nice to get some random data input from other owners...

 

[ToxicDoc]

That's a pretty standard temperature of any AC system. You can't have it go too much lower (maybe down to 2 C) because that would create the risk of the evaporator freezing (humidity in the air freezing on it)

 

[yurtesen]

That's a pretty standard temperature of any AC system. You can't have it go too much lower (maybe down to 2 C) because that would create the risk of the evaporator freezing (humidity in the air freezing on it)

Thats what I thought, but I wanted to see what others get for evaporator temperature.

 

[oilhammer]

The COLDEST part of the system will be right after the pressure drop, be it at the expansion valve (like the car in question here) or the orifice tube (like a B5 Passat, the big Audis, etc.). And that will be calibrated to only get to "right above" freezing, usually with a few degrees of margin above freezing.

Otherwise, the condensate on the evaporator will freeze to a block of ice, blocking air flow.

Since no evaporator can exchange at 100% of the coldest parts, we try and look for a drop from ambient, not an actual value by itself. Usually a 30 to 40 F drop is normal, measured at the vents. Slower air speed allows a greater drop in temp, because the air is in contact with the evaporator for longer, which is why you see a lower vent temp at a lower blower speed, but not enough volume to cool the cabin quickly from a hot soak.

Even with a properly maintained cabin filter, eventually the evaporator slowly gets gunked up and will lose its ability to exchange the heat. When I did my one Golf's evap case a couple years ago, I had no "problem" with the A/C ability to cool the cabin, but the new one cools it MUCH better simply because it is CLEAN. My old one was really dirty, easily a third of the core's fins were blocked off.