Climate control 1997 SL320 working or not

[r129MAN]

Hi
Hope someone can help, I am unsure whether my climate contol is working correctly or not. Switching it on to auto initially and at a temp of 24 deg C all seems fine & hot air blows around the car and the cabin warms up, then after a while even though there are 2/3 bars indicating that the blower is on no air appears to be flowing anywhere, increasing temp still does not make a change, is it that the interior temp has reached its set point & therefore the air is directed elsewhere until a large temp drop is sensed by the system. If I switch it all off and wait a while ( 20-30 mins) then switch it on again then you can feel the warm air blowing again at the footwell or windscreen demister, when no air flows even if I turn on the windscreen demister and the fan indicates full flow no air comes out of the vents. Am I concerned about nothing and this is the way climate control works or could I have fault. If yes to a fault any ideas what the problem could be.

 

[television]

I have a feeling that my 129 went like that, what happens if you increase the temp

 

[whitenemesis]

Sounds like normal "Auto" function up to the point where you turn on the demist. That should always blow onto the screen, at max flow, no matter what other settings are.

 

[r129MAN]

When it seems to go wrong, increasing the temp does nothing.

 

[r129MAN]

I have a feeling that my 129 went like that, what happens if you increase the temp

Hi Television
What did you do with your system?

 

[jfdi]

Climate control not working - any updates?

Hi - Does anyone know if this problem was resolved? I've just become the proud owner of a 99 SL500 with exactly this issue, very cold inside on a 4 hour drive and 3Celsius outside!
Rgds
Jim

 

[television]

Hi - Does anyone know if this problem was resolved? I've just become the proud owner of a 99 SL500 with exactly this issue, very cold inside on a 4 hour drive and 3Celsius outside!
Rgds
Jim

Mine was a 99,,, if there is no air coming from the flaps,,could it be a vacuum problem

http://www.detali.ru/cat/oem_mb2.as...GA=722.607&CT=F&cat=44F&SID=80&SGR=120&SGN=05

Most of the flaps are vacuum controlled

 

[television]

I am thinking ,,is there an ambient sensor that could fail ,,this could be more probable, I never solved the one that I had,,but it always started off fine, and I got colder and colder the further I drove. I will do some looking into this

 

[jfdi]

Further exploration of the forum turned up this post which describes a very similar problem and the resolution:
http://forums.mercedesclub.org.uk/showthread.php?t=18949&highlight=climate+control+SL

I had a similar fault on an old Jeep Cherokee - that ended up breaking the A/C compressor so I hope that hasn't happened...

I'm off to see if running in Eco mode helps...

Rgds
Jim

 

[television]

Further exploration of the forum turned up this post which describes a very similar problem and the resolution:
http://forums.mercedesclub.org.uk/showthread.php?t=18949&highlight=climate+control+SL

I had a similar fault on an old Jeep Cherokee - that ended up breaking the A/C compressor so I hope that hasn't happened...

I'm off to see if running in Eco mode helps...

Rgds
Jim

Got to find that sensor Jim

 

[malcolmm]

R129 Climate problem

Hi all,

My turn to give something back to the forum, for a change. Hopefully this might solve your air-con problem as it did mine.

For a year, I battled with an air conditioning problem. Air stopped venting into the vehicle after 30 minutes or thereabouts, even though the fan was running and I could feel hot or cold behind the vents when I changed the temperature.

To cut a long story short, I got the following advice. Turned out to be a sensor. My local garage were a bit reluctant when I told them exactly what I wanted doing, but below is the advice I was given - it saved me changing the heater control panel (garage advice) and it has worked fine ever since:

---------------------------------------------
Service operation: 83 8054 01 "Temperature sensor on evaporator replace"
Part number: A 210 830 07 72 "Temperature sensor"

Sounds like your evaporator temperature sensor has failed. This causes the evaporator to ice up. You can check it on the pushbutton control module. There is also a technical bulletin about this problem.

It is a very cheap and easy repair. New sensor is about US$50 and can be fitted in the blink of an eye.





You can test the evap temp sensor using the diagnostic feature on the a/c push button control unit.

Come to your car in the morning or when it has been standing for a few hours (so the engine and heater are cold). Turn the ignition on, without firing the engine. Run the self-diagnostic routine on the air con pushbutton control panel and check the evaporator temperature reading. If the sensor is faulty, you will have a logically impossible value:

1. Turn ignition on (without firing engine)

2. Set the air con temp to 72 deg F or 22 deg C

3. Press "REST" for more than 6 seconds

4. The left side of the display will alternately display "01" (which is the test number) and the cabin interior temperature (eg 72 deg F or whatever the temp in the car happens to be).

5. Press the fan speed "+" button to advance to the next test (eg "02").

6. The evaporator temperature is test number "05". The working temperature of the evaporator is between 2 deg C and 12 deg C. Obviously, if your car has been left overnight and has not been started, the value returned should be consistent with the ambient exterior temperature. So if it is about 12 deg C outside, the sensor should return about 12 deg C also. If the evaporator temperature sensor is broken it will return a logically inconsistent value, eg 40 deg C.

7. Now turn on the car and run the a/c for a few minutes. Repeat the procedure above. Test "05" which is the evap temp sensor, should return a value of 2 to 12 deg C if it is working. If it is broken, it will return an impossible value, such as 40 deg C.

The other tests on the push button control unit are great:

01: in car temp sensor
02: outside temp sensor
03: heater core temp sensor
05: evap temp sensor
06: ECT temp sensor
07: refrigerant pressure meassured in BAR
08: refrigerant temp sensor

21: engine speed
22: vehicle speed

There are loads more.

Part No. 2108300572….or 1298300072

Heating and ventilation …heater case


Service operation: 83 8054 01 "Temperature sensor on evaporator replace"
Part number: A 210 830 07 72 "Temperature sensor"







Nr. Description Unit

01 In-car temperature sensor °C
02 Outside temperature sensor °C
03 Left heat exchanger temp. sensor °C
05 Evaporator temperature sensor °C
06 Coolant temperature sensor °C
07 Refrigerant pressure bar
08 Refrigerant temperature sensor °C
09 Not assigned --
10 Blower control voltage Volt
20 Auxiliary fan control current mA
21 Engine Speed x100 RPM
22 Vehicle Speed km/h
23 Circuit 58d (% of batt. Voltage) %
24 Battery Voltage Volt
40 Software staus
41 Software staus
42 Variant Code 1st numerical value
43 Variant Code 2nd numerical value
50 Not assigned
51 Not assigned
52 Not assignd
60 Roof OPE/CLO
61 Left side air outlet, knurled wheel
potentiometer Volts
62 Vacuum actuator 46, feedback
potentiometer Volts
63 Center outlet, knurled wheel
potentiometer Volts
64 Vacuum actuator 47, feedback
potentiometer Volts
65 Right side air outlet, knurled wheel
potentiometer Volts
66 Vacuum actuator 48, feedback
potentiometer Volts

Item 63 is the input signal from the thumbwheel control for the center vent, and 64 is the feedback signal to the controller giving it the position of the vent flap. As you move the thumbwheel these values should continously vary from a minimum of roughly .7 to 4.5.

The original part number was A1298300072 - it has been superceded by A2108300572 which is £28. It is located under the dash on the drivers side by the centre console housing - you just need to drop the trim panel for access.

 

[television]

Thank you very much for the above information

 

[Dale Minton]

Hi all, I'm new to this forum but not to Mercs - and it would seem a lot of you know your stuff.
I've enjoyed 2 1993 W124 500E's (brilliant), 1 1993 500SL and a 2002 SL500 -not all all the same time mind you. Times are a little hard right now so I sold the SL500 and bought an 1998 SL320 and I've a niggle with the Climate Control which I hope someone may help me with. The LCD screen on the dashboard control unit had a small fracture so I tracked down a used control unit with the same part no, so there's no problem there (I hope)
Essentially there are 3 issues that are bothering me.
Issue 1:-
The climate seems to be working fine but the centre vents do not open when the thumbwheel is turned to do so, and the outer vents are always on, they will not close when the their outer thumbwheels are closed.
Issue 2:-
This revolves around the red and blue buttons between the centre vents. When I had my '93 500SL the lights within these switches never illuminated unless they were pressed. On this current SL they are lit all the time, the only time the Red one goes out is if you crank up the temp on the climate and once the car gets somewhat warmer. The only time the Blue one goes out is when you crank the cold really low. The buttons don't seem to do anything (they don't switch them on when there off or visa versa).
Issue 3:-
This may not be a problem at all, but I wanted to ask. When the climate is on Auto the fan always seems to settle at mark 3 up the scale, is this correct, or should it go down further once a certain temp has been reached.

Can someone enlighten me and a Happy Christmas to you all.
Dale

 

[television]

Welcome Dale to the forum,,, its too late tonight to think about this, bring it to the light earlier tomorrow night as the post may get lost

 

[jfdi]

Thanks to all...

Just a quick note to confirm the problem of "no air form the vents" was indeed the result of a faulty evaporator sensor, as suggested in earlier posts.

Two ways of confirming the diagnosis:
1 Run the Climate Control in Eco mode turns off the air con and thus prevents the heat exchanger freezing over.

2 Put the Climate Control into diagnostic mode and look at entry number 5, the evaporator sensor. Mine was reading a constant 44, clearly wrong.

I eventually convinced my local dealership that the sensor was the problem and they replaced it a couple of days ago.

Climate Control now working perfectly, and evaporator sensor reading between 2C and 8C.

Thanks to everyone for their help.

Best regards and happy new year to all
Jim

 

[television]

The same to you and thanks for posting back Jim