Normal climate control A/C operation

[nice1guv]

I have a 2004 update model diesel with climate control, and was just wondering what the normal operation is for the A/C.
Mines seems to vary the time it takes for the A/C to kick in.

You turn on the climate control with the fan on low (lets say 3 bars),
the temp is set at the minimum (16C for me, ~60F for US?),
the air is towards your face (although it doesn't matter where it goes),
set to re-circulate,
outside temp is 25C, 77F,
Press the A/C button.

How long does the A/C actually take to kick in?
Is it instantly when you press the button, or does it take a few minutes?

I've started the car from cold and it has kicked in instantly, but usually it takes a few mins of driving before it starts.
When the car is hot, it still generally takes a few mins of driving as well.
If you stopped the car for a short while and then restarted, the A/C starts straight away.

Once it is going, it is freezing cold and will run continuously for however long it is on for.

Is this normal A/C operation?

[TerminatorX5]

from WDS

A/C Compressor Activation



Function

The A/C compressor is controlled as follows:
•Operation of the air conditioning button

•Transmission of the request via the Central Gateway Module (ZGM) to the digital engine module DME/DDE

•Setting of the operating mode ”Air conditioning on” by the DME/DDE

•Transmission of the status from the DME/DDE via the powertrain CAN to the ZGM

•Transmission of the request from the ZGM via the K-CAN to the air conditioning control unit

•Activation of the air conditioning compressor


The A/C compressor is switched off in precisely the same way.

This procedure ensures that at the time the air conditioning compressor is switched on, the engine has sufficient power reserves. Activation of the A/C compressor does not bring about a dip in engine speed.

Diagnosis

In the event of a fault, the entire signal path must be checked.


here is more, i think this applies to diesel:

A/C power output DDE 5.0

The A/C compressor is switched on and off by the DDE control unit via the A/C comporessor relay. The DDE control unit receives a request via the CAN bus from the heating and air conditioning control unit to switch on the air conditioning compressor.

If a request to switch on the air conditioning compressor is received, the DDE control unit checks whether there are conditions prevailing that do not allow the compressor to be switched on. The DDE control unit then switches the air conditioning compressor relay on or off accordingly. Switch-on of the A/C compressor is inhibited by the DDE control unit under following conditions:
•Start-off status:
Road speed < 9 km/h AND
Accelerator pedal > 31 % AND
Engine speed < 1750 rpm

•Coolant temperature > 118°C

•Throttle dip:
Engine speed < 660 rpm

•while starting

•one of the following faults stored on the DDE:
◦3F10, 3F20, Pedal position sensor

◦3F60, Road speed signal

◦4670, Supply voltage 1

◦4690, Supply voltage 3




Troubleshooting

Control of the air conditioning compressor relay is monitored. The following faults are monitored:
•4100, Activation short circuit to B+

•4101, Activation short circuit to B-

•4102, Activation circuit break

•4103, Excess temperature output stage

[nice1guv]

Thanks, very good info!

Hmmm, I take it this isn't normal operation then.
So when you press the A/C button it should instantly start.

I'll have to hook up DIS again, but last time I did it, I'm sure there were no codes stored for the relay (but I may have cleared them without looking into them fully ).

[Qsilver7]

If you have the auto IHKA (digital) control unit...is there a reason you're not using the AUTO fan feature, too? The auto feature will select fan speed as well as TEMP. To select auto fan speed...press the AUTO button until you see the word "auto" appear in the fan speed display. If "auto" is not illuminated in the fan speed display...then you're operating under manual fan speed selection.


Both the temp and fan speed can be taken out of "auto" mode...and the system may not respond as quickly with your manual settings.

Also make sure that the stratified air dial (the one in the middle of the dash's center vent) isn't turned to the RED area (warmed air will flow from the dash vents):

There's also the MAX cooling pre-programmed button that you can use on very hot days:

e39/e53 auto IHKA control panel (with neither auto temp nor auto fan speed selected)

[nice1guv]

Thanks Qsilver7.

I do have the air temp dials set to the 3 blue marks.

I also have the auto climate control as pictured.
I generally don't use the auto setting though, as it puts the fan speed up too high for my liking.

Even when I run the max A/C setting, it doesn't kick in any quicker (I tried it yesterday).

I haven't had a chance to connect DIS yet and see if there are any faults logged,
but there is something that holds the A/C back until it decides to kick in.

I'm not sure what the trigger is yet, but when it starts there is a strange sort of whoosh sound it makes and the air instantly then becomes freezing cold.
On a warm day, the air coming out the vents can be so cold that it looks like fog, like when you open the freezer on a hot day and the cold air escapes.

[four.8is]

Don't know if it was mentioned, but MAX AC button will activate the previous temp setting for 15min? while the car is off.
I love that option as it keeps the car warm if you have to run in the house /store on a cold winter day but don't want to keep the engine running-> (for thieves)

[nice1guv]

I've quickly run DIS now, but no faults were logged with the IHKA module or anything else that would affect the A/C.

I activated the electric fan through DIS and it came on immediately.

I displayed all the A/C control values and couldn't see any odd ones.
Temps were all good, and as soon as I hit the A/C button, it showed up as active and the compressor began spinning at 600/700 rpm.

Hmmm, will have to interogate the displayed values a bit more I think.
Only had a quick look, so maybe there is more to see there - I hope!

Any ideas more than welcome.

[Qsilver7]

Originally Posted by four.8is

Don't know if it was mentioned, but MAX AC button will activate the previous temp setting for 15min? while the car is off.
I love that option as it keeps the car warm if you have to run in the house /store on a cold winter day but don't want to keep the engine running-> (for thieves)

Yes...that is a great feature for those that live where temps can get cool...but the residual heat feature can only be initiated when ambient temps are below 59° F / 15° C.