A/C not blowing cold + electric fan always on (when car on) - UV dye shows nothing
Thread Starter
Member
Joined: Oct 2009
Posts: 214
Likes: 38
From: East Idaho
2014 GL450, 2006 S500, 2003 ML350, 1996 C280 (Prev 1995 C220, 2002 CLK320, 1980 300SD Turbo)
A/C not blowing cold + electric fan always on (when car on) - UV dye shows nothing
After I bought my C280, I evacuated the A/C system:
Left the vacuum on for 30 minutes, turned it off. Let it sit for 30 minutes longer to ensure no leaks in the system and gauges looked good holding vacuum. Charged it with 25 or so oz. of refrigerant and enjoyed super cold A/C for about a week and now it blows hot air.
So I repeated the process, this time with UV dye added, drove for a couple days, a couple hours each day and inspected the hoses, valves and compressor with a black light and only see dye around the low pressure shrader valve (where I just think it went in.)
Either related or not, my electric fan is always on when you start the car.
I'm going to change the A/C temperature sensor that is by the gas pedal but I think there is another temperature sensor near the front of the engine.
Any thoughts on either condition and whether they may be related?
Thanks!
Left the vacuum on for 30 minutes, turned it off. Let it sit for 30 minutes longer to ensure no leaks in the system and gauges looked good holding vacuum. Charged it with 25 or so oz. of refrigerant and enjoyed super cold A/C for about a week and now it blows hot air.
So I repeated the process, this time with UV dye added, drove for a couple days, a couple hours each day and inspected the hoses, valves and compressor with a black light and only see dye around the low pressure shrader valve (where I just think it went in.)
Either related or not, my electric fan is always on when you start the car.
I'm going to change the A/C temperature sensor that is by the gas pedal but I think there is another temperature sensor near the front of the engine.
Any thoughts on either condition and whether they may be related?
Thanks!
Thread Starter
Member
Joined: Oct 2009
Posts: 214
Likes: 38
From: East Idaho
2014 GL450, 2006 S500, 2003 ML350, 1996 C280 (Prev 1995 C220, 2002 CLK320, 1980 300SD Turbo)
Any help with readout interpretations would be appreciated:
01 In-Car Temperature Sensor with Aspirator Blower (B10/4) - "OPE"
02 Outside Temperature Sensor (B14) - "77 degrees" (accurate)
03 Heater Core Temperature Sensor (B10/1) - "OPE"
05 Evaporator Temperature Sensor (B10/6) - "CLO"
06 Engine Coolant Temperature Sensor (ECT) (B11/4) - "212" (wtf?)
07 Refrigerant Pressure in Bar : "CLO"
08 Refrigerant Temperature Sensor (B12/1) - "HI"
09 Not Used - "129" (if it not used why am I getting a value)
10 Blower Control Voltage - "175"
20 Control Current for Auxiliary Fan exp. : 7 = 7 mA = 04 degrees 0 (??)
21 Engine RPM. example 00..99 (x100) = 9900 - 240
22 Vehicle Speed - 050 (vehicle was stationary)
23 PIN 58D exp. 99.0 = 99% of Battery Voltage- 050
24 Battery Voltage : 12.8 = 12,8 Volt
40 A/C Controller Software Version Coding - NOT DISPLAYED
41 A/C Controller Hardware Version - NOT DISPLAYED
42 Variant code 1 - NOT DISPLAYED
43 Variant code 2 - NOT DISPLAYED
50 Not Used - 77
51 Not Used - 72
52 Not Used - 50 F degrees
54 ON/OFF A/C Compressor emergency off signal from engine control module. - OFF
DTCs were
226 In-Car Air Temperature Sensor (B10/4)
228 Heater Core Temperature Sensor (B10/1)
230 Evaporator Temperature Sensor (B10/6)
232 Refrigerant Pressure Sensor (B12)
233 Refrigerant Temperature Sensor (B12/1)
422 Serial Interface Connection (K1) to Instrument Cluster (IC)
My obvious questions are as follows:
1) What does open and closed mean on reading values?
2) How am I getting values for things that are not used ?
3) Is it actualyl possible that all five of those sensors are bad? Is there a central place they all go that could be the problem?
Any insight would be highly appreciated.
01 In-Car Temperature Sensor with Aspirator Blower (B10/4) - "OPE"
02 Outside Temperature Sensor (B14) - "77 degrees" (accurate)
03 Heater Core Temperature Sensor (B10/1) - "OPE"
05 Evaporator Temperature Sensor (B10/6) - "CLO"
06 Engine Coolant Temperature Sensor (ECT) (B11/4) - "212" (wtf?)
07 Refrigerant Pressure in Bar : "CLO"
08 Refrigerant Temperature Sensor (B12/1) - "HI"
09 Not Used - "129" (if it not used why am I getting a value)
10 Blower Control Voltage - "175"
20 Control Current for Auxiliary Fan exp. : 7 = 7 mA = 04 degrees 0 (??)
21 Engine RPM. example 00..99 (x100) = 9900 - 240
22 Vehicle Speed - 050 (vehicle was stationary)
23 PIN 58D exp. 99.0 = 99% of Battery Voltage- 050
24 Battery Voltage : 12.8 = 12,8 Volt
40 A/C Controller Software Version Coding - NOT DISPLAYED
41 A/C Controller Hardware Version - NOT DISPLAYED
42 Variant code 1 - NOT DISPLAYED
43 Variant code 2 - NOT DISPLAYED
50 Not Used - 77
51 Not Used - 72
52 Not Used - 50 F degrees
54 ON/OFF A/C Compressor emergency off signal from engine control module. - OFF
DTCs were
226 In-Car Air Temperature Sensor (B10/4)
228 Heater Core Temperature Sensor (B10/1)
230 Evaporator Temperature Sensor (B10/6)
232 Refrigerant Pressure Sensor (B12)
233 Refrigerant Temperature Sensor (B12/1)
422 Serial Interface Connection (K1) to Instrument Cluster (IC)
My obvious questions are as follows:
1) What does open and closed mean on reading values?
2) How am I getting values for things that are not used ?
3) Is it actualyl possible that all five of those sensors are bad? Is there a central place they all go that could be the problem?
Any insight would be highly appreciated.
Thread Starter
Member
Joined: Oct 2009
Posts: 214
Likes: 38
From: East Idaho
2014 GL450, 2006 S500, 2003 ML350, 1996 C280 (Prev 1995 C220, 2002 CLK320, 1980 300SD Turbo)
Loads of fun! That's part of why I enjoy these cars, the intellectual exercise of diagnosis and learning more about what's going on - of course I say that when I can figure it out eventually, other times when I want it to go away I forget all about that 
I changed the Evap temp sensor under the dash and the electric fan stoppped going constantly! So there is half my problem(I think.)
I didn't take sensor measurements yet, but after clearing codes and driving for 2 hours, the only pending code is 421 - which I think is the pulse module.
When I turn on the car sometimes a loud THWAP comes from behind the glove box, always has since I owned the car. I've always assumed it was some port on the A/C (it makes that sound when you turn off the A/C unit too sometimes) but since initially didn't make the air not-blow-cold I ignored it.
I'll post my findings and thanks again!
I changed the Evap temp sensor under the dash and the electric fan stoppped going constantly! So there is half my problem(I think.)
I didn't take sensor measurements yet, but after clearing codes and driving for 2 hours, the only pending code is 421 - which I think is the pulse module.
When I turn on the car sometimes a loud THWAP comes from behind the glove box, always has since I owned the car. I've always assumed it was some port on the A/C (it makes that sound when you turn off the A/C unit too sometimes) but since initially didn't make the air not-blow-cold I ignored it.
I'll post my findings and thanks again!
Last edited by RollTideW163; Aug 7, 2017 at 12:01 PM.
MBWorld Fanatic!
Joined: Dec 2004
Posts: 4,268
Likes: 253
an 11 year old s600 is a toy? no. it is a blah, outdated, one (right) rwd, uncool method of transportation for elderly folks. yes, it is not hard to fix and maintain, but there will be a constant stream of repairs which will sap the last few bits of fun of owning it... if you wanted an old toy you should have gotten a well cared for 2005-2007 sl65 amg. now that is a toy... 
good luck with your new car though. if you like it that is all that matters...
good luck with your new car though. if you like it that is all that matters...
Newbie
Joined: Apr 2021
Posts: 4
Likes: 0
S211
Can someone enlighten me how I do a self diagnostics on the AC system. I have a c180 Kompressor 2008 estate. Is there an evap temp sensor under the dash? I also have the AC not working and the engine cooling fan on all the time.
