Climatronic issue

[kaneda]

When i turn the car on the temp reading on the climatronic reads low and then starts to drop (as low as -3 ;p ) and the issue I have is that when the temp gets lower than 4 deg the A/C turns off
From what I understand there is a temp sensor just under the cabin pollen filter that controls this . Any one know what its called and how i go about replacing it or if i can just replace it with a resistor to fix the temp at one reading ?
Its been playing up for a while now but with the onslaught of summer kinda a pain not being able to turn the A/C on because the car thinks its below freezing

[kaneda]

Well I pulled out every temp sensor in the car today to do some tests and still can not work out which one is the cause.
I did discover that they are all simple to remove/replace so might look at replacing all 3 n see how i go ..............

[whiteVR6]

it sounds like the control unit is playing up

[graeme86]

The temperature shown for the outside display comes from a sensor in the front left bumper grill (passenger side).

The temp sensor in the air inlet under the pollen filter is just used to re-adjust the inside temperature - it does not display on the control unit readout.

The temp sensor for the perceived overall inside temperature that the climatronic uses to adjust the airflow with is behind one of the little grills on the face of the unit.

The inside temperature on the display is just the temperature you dial in, but it shouldn't change by itself.

You can put the climatronic into diagnostic mode and it will hopefully tell you what the exact fault is - plenty of threads on internet on how to do this.

No need to spend any money just yet.

[kaneda]

I was under the impression that the sensor on the front bumper was for the temp reading on the MFD ?
I thought the climatronic used a combination of the temp of the incoming air with the cabin temp to operate the A/C which is why it has the sensor under the pollen filter and the sensor in the drivers side foot well.
Ive done the self test a few times with no errors displayed and same when i hook up the v-checker

Oo and befor i forget the colder i set the desired temp the quicker and crazy low the measured temp goes eg if I set the desired temp to 24 then the displayed temp on the left side will slowly drop to 11 where as if i set the temp to low then the displayed temp on the left drops quickly to 3 or below and at this point the a/c turns off :p (out side temp is a lovely 30pluss and 110% humidity )

[graeme86]

The outside temp also displays on the MFA from the same signal from the bumper sensor - does that also drop as well?

The sensor signal goes direct to the climatronic unit and then the signal gets sent from the climatronic unit to the MFA the way it is wired.

"I thought the climatronic used a combination of the temp of the incoming air with the cabin temp to operate the A/C which is why it has the sensor under the pollen filter and the sensor in the drivers side foot well."

That is correct - all the temp sensors are used to calculate the air blending required - I just meant the temp display readout in the unit is not generated by the pollen filter sensor.

[kaneda]

I have an older golf so it doesn't have the MFA
I did unplug each of the three sensors i know about (front bumper ,under pollen filter and drivers foot well ) one at a time and turned the system on to see if it made a difference and if it logged any errors and none made a diff to the figures on the display but only the in car sensors logged a fault when they were disconnected.

[kaneda]

Bit of an update...............
So i ordered 2 new sensors (Fresh air duct and footwell vent) and installed them with no change in issue!
Went over to Jays and got him to have a fiddle with VCDS and this is the info it gave us
I measured the ambient air temp not going off the cars readings and it was 33c .

Calculated air temp 5c (this is a problem)
Fresh air duct 45c (Car running with bonnet closed I guess this sounds about right )
Outside air temp 18c (I wish , but no)
Center vent (G191) -53c (sure buddy , is this the reading from the climatronic unit ?)
foot well (G192) 42c (maybe )
Dash panel (G56) 34c (another maybe)

So with those numbers I first had a fiddle with the outside air temp sensor by spraying it with hot air, cold spray and removing the sensor and replacing it with resistors of various values but couldnt get the temp to raise above 18c ? going to order a new one anyways.....
The more info i get on the climatronic the more confusing it gets as if one sensor fails it gets its reading from somewhere else or defaults to a set value..
I have disassembled the climatronic unit and cleaned out the years of dust and sprayed the inside with contact cleaner and checked that the little fan thingy still operates and that didnt get me anywhere either.
Should i try a new climatronic unit ?

[h100vw]

Whats the part number of that bit Steve? I have the gear from the A3, pretty sure that looked like the stuff in the last mk4 I was in.

Gavin

[kaneda]

vw part number is 3B2 907 044 B
Hella number is 5HB 007 617-11 (the dash 11 part changes between types)

[graeme86]

It would be good if you could just plug in another head unit to see if that fixes the problem.

You can also get the headunit into its own diagnostic mode and see what codes it displays itself.

I wonder if its just a simple wiring fault in the harness from the outside air temp sensor - incorrect resistance would give wrong temp display

[h100vw]

vw part number is 3B2 907 044 B
Hella number is 5HB 007 617-11 (the dash 11 part changes between types)

Will check it out in a few minutes when I have had my tea.

Gavin

[kaneda]

Ordered a replacement unit today for $83 delivered so will see how that goes............

[kaneda]

Well the unit arrived today and i was a bit concerned about its condition but a quick clean up and all looks fine.
5min install job and so far it seems to have solved the issues but I am yet to hook up VCDS to check what the sensors are reading

[kaneda]

Well not 100% new unit continues to log errors and flash crazy every time the unit is turned on . Unit dose display correct temp and dose operate the a/c but doesn't control fan speed correctly (all out or nothing ) doesn't see the light sensor on the dash and dose the flash thing on start up.
So emailed the supplier to see if i can get a replacement