Air-con pump always active

I've been monitoring the heating/cooling system of my diesel Golf Mk 7 and used VCDS to create a plot of the three pumps (see graph).

I was surprised to find the aircon pump (light blue line in the chart) is switching on and off at regular intervals even though I have the heating at max, blowers directed as my face and aircon switched off. Is this normal?

It is switching on every 35 seconds and staying on for 6 seconds. At about 16 mins it stays on longer and this pattern happened the following day on the same journey.

Here is the key:
Dark blue - Engine speed diving by 25
Orange - Vehicle speed
Grey - Heater support pump 1 bank 1 second.circuit: activat.
Yellow - Heater support pump 1 bank 1 primary circuit: activation
Light blue - Heater supp.pump 1 bank 1 charg.air cool.circuit: activat.

I'm wondering if this is why my heating is not as hot as it should be.

The chart is of a 25 minute drive, mostly on the motorway at 50mph (M3 roadworks!).

Any information much appreciated.

Do you have the air supply switched to windshield, or windshield plus feet? Since air-conditioned air is drier than outside air, some cars enforce using A/C when you are defrosting the windshield. (Not sure about the mk7.)

(Oh, I guess you said directed at your face.)

Yep, at my face so it shouldn't be trying to dry the air.

I hate that the ac pump is on so frequently. I just want it on when I actually use ac.

rick1024 said:

I hate that the ac pump is on so frequently. I just want it on when I actually use ac.

Click to expand...

Do you think this is normal and by design?

I don't know the reasoning behind it, but its been discussed here before, our AC unit never completely turns off.

Maybe to always keep it warmed up and ready? Not sure, but this is normal.

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Our compressors are variable displacement so they never actually shut off like the old school clutch system. Most likely, the HVAC system uses it for some type of temperature control and or system equalization.

That's a shame. Guess that's not my cool heating problem then!

Thanks for the replies.

What is the air temp at the center vent with the heater on full? The compressor being on for 6 seconds is not enough time to cool the system down to impact your air temp.

Currently the center vent is 60 degrees which is ok. But that's only happened the last couple of weeks. Prior to that I was getting more like 45 degrees. I posted another blog about it.
I don't know if it will stay at 60 when winter arrives or drop again. VW told me in January that another Golf was giving 73 degrees.