>9/95 climate control cabin air HEAT problem. - Mercedes-Benz Forum

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Old 02-10-2010, 05:49 PM   #1 (permalink)
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Date registered: Jul 2006
Vehicle: Y2K SL500 Silver
Location: So. California
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>9/95 climate control cabin air HEAT problem.

I took about 110 mile drive today and the outside temp was reading 66 degrees F so I closed off all of the upper vents so everything was directed to the floor to warm my feet to about 74 F with the fan on #2. This normally works but later today I found that in order to get any heat I had to up the temp to a 83-84 F and a fan setting of #5-6 in order to get the same comfort that I normally get at 74 F.

The R107's have what is known as a Monovalve that needs replacing whenever you expierence my kind of situation. Do you think that my car could use a new Monovalve (Y19) or Heater core temp sensor (B10/2) or Interior air temp sensor (B10/4)?
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Old 02-10-2010, 06:24 PM   #2 (permalink)
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Originally Posted by lynns View Post
FWIW, I decided to take some baseline readings by following the above Climate Control, etc. procedure for data collection. Here are the values I received on 8/5/07.

Sensor# - Description - Unit Value

01 Inside temperature °F = 74
02 Outside temperature °F = 79 (sitting still, engine running)
03 Heater core exchanger temp. °F = 58
05 Evaporator temperature °F = 47
06 Engine coolant temperature °F = 192
07 Refrigerant pressure Bar = 14
08 Refrigerant temperature °F = 127
10 Blower control voltage = 12.5
20 Auxiliary fan control current mA = 00
21 Engine Speed x10 RPM = 0600
22 Vehicle Speed MPH = 000
23 Circuit 58d (% of batt. Voltage) % = 000
24 Battery Voltage = 13.9
40 A/C Controller Software Version = 03
41 A/C Controller Hardware Version = 03
42 Variant Code 1 = 11
43 Variant Code 2 = 6-C
60 Roof OPE/CLO = open
61 Left side air outlet(open), knurled wheel potentiometer Volts = 4.0
62 Vacuum actuator 46, feedback potentiometer Volts = 3.5
63 Center outlet(open), knurled wheel potentiometer Volts = 4.1
64 Vacuum actuator 47, feedback potentiometer Volts = 3.5
65 Right side air outlet(closed), knurled wheel potentiometer Volts = 0.8
66 Vacuum actuator 48, feedback potentiometer Volts = 0.9
I decided to take some more readings by following the same Climate Control procedure for data collection. Here are the values I received today, 2/10/10.

Sensor# - Description - Unit Value

01 Inside temperature °F = 75
02 Outside temperature °F = 72 (sitting still, engine running)
Note: the outside thermometer read 59 (sitting still) and the climate Control dropped from 72 to 59 after taking a short drive.
03 Heater core exchanger temp. °F = 74
05 Evaporator temperature °F = 39
06 Engine coolant temperature °F = 195
07 Refrigerant pressure Bar = 13
08 Refrigerant temperature °F = 109
10 Blower control voltage = 8.0
20 Auxiliary fan control current mA = 00
21 Engine Speed x10 RPM = 0600
22 Vehicle Speed MPH = 000
23 Circuit 58d (% of batt. Voltage) % = 000
24 Battery Voltage = 13.9
40 A/C Controller Software Version = 03
41 A/C Controller Hardware Version = 03
42 Variant Code 1 = 11
43 Variant Code 2 = 6-C
60 Roof OPE/CLO = closed
61 Left side air outlet(open), knurled wheel potentiometer Volts = 4.0
62 Vacuum actuator 46, feedback potentiometer Volts = 3.8
63 Center outlet(open), knurled wheel potentiometer Volts = 4.1
64 Vacuum actuator 47, feedback potentiometer Volts = 3.8
65 Right side air outlet(opened), knurled wheel potentiometer Volts = 4.0
66 Vacuum actuator 48, feedback potentiometer Volts = 3.8

Last edited by lynns; 02-15-2010 at 12:19 AM.
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Old 02-11-2010, 10:51 PM   #3 (permalink)
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Please help with cabin air heat problem.

Just like a woman my cabin air heater was working just fine today.
It may be a temporary thing with nothing more to worry about. Just like a woman.
Since she is my Garage Queen and she isn't driven every day.

I think it could have something to do with the (see attached PDF's for >9/95 cars)
1) Monovalve
"The heater core heats up the air flowing through the air ducts into the vehicle passenger compartment. The heat given up by the heater core is regulated by the monovalve controlling the quantity of heated coolant flowing through. The monovalve is controlled by the pushbutton control module."
MB p/n 0008307284 and Bosch p/n 1147412037 @ $105.51

2) Heater core temp sensor
"The heater core temperature sensor is a temperature-dependent resistor. The measured resistance is transferred to the pushbutton control module. Here the reading (actual value) is compared with the temperature set on the pushbutton control module. Each temperature setting is associated with a resistance (nominal value). The pushbutton control module determines the opening time for the monovalve by comparing the actual value and settings."
MB p/n 1268301772 @ $22.92
Attached Images
   
Attached Files
File Type: pdf Monovalve location.pdf (32.7 KB, 307 views)
File Type: pdf Heater core temp sensor location.pdf (28.5 KB, 323 views)

Last edited by lynns; 02-15-2010 at 12:21 AM.
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Old 02-13-2010, 07:24 AM   #4 (permalink)
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Quote:
Originally Posted by lynns View Post
...I found that in order to get any heat I had to up the temp to a 83-84 F...
If everything seemed to work fine with the exception that you had to dial a higher temperature to get heated air, then in this instance the first thing I would look at through diagnostics is the in-car temperature, 01 on the menu. Possibly the controller is being signaled that it is warmer in the car than it actually is.

All of the sensor readings you posted look reasonable to me, Lynn.
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Old 02-13-2010, 03:50 PM   #5 (permalink)
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Originally Posted by bobterry99 View Post
If everything seemed to work fine with the exception that you had to dial a higher temperature to get heated air, then in this instance the first thing I would look at through diagnostics is the in-car temperature, 01 on the menu. Possibly the controller is being signaled that it is warmer in the car than it actually is.

All of the sensor readings you posted look reasonable to me, Lynn.
Bob, do you know if a SDS can tell if my my Interior air temp sensor (B10/4) is functioning or not??

Please see the attached PDF.
Attached Files
File Type: pdf R&R interior air temp sensor.pdf (62.9 KB, 303 views)
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Old 02-13-2010, 04:06 PM   #6 (permalink)
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Interior air temp sensor

Or it could need a new Interior air temp sensor. It's connected to an aspirator blower that's located in the cabin light rear view mirror assembly (it shows as B10/4 in the attached PDF).

The R129 DVD says, "The interior air temp sensor is equipped with an aspirator blower which continuously sucks air out of the vehicle passenger compartment for measurement of the temperature. It is connected to the pushbutton control module by a separate electric lead. The aspirator blower provides continuous circulation of the interior air around the interior air temp sensor to ensure a high degree of control accuracy."

After reading several forums it was suggested that I should take a piece of tissue paper, with the heater on, and see if the tissue paper would get sucked onto the grill when I held it close to it. Somewhere in the dash there is a small vacumn pump that links to the sensor that sucks air. It then uses that air to check how hot the cabin air is. If the sensor is broken or the grill is blocked the heat in the cabin will be effected no matter where you have the setting set to. On my car the tissue test appeared to failed for the Interior air temp sensor (B10/4).

Last edited by lynns; 02-16-2010 at 10:52 PM.
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Old 02-14-2010, 04:51 AM   #7 (permalink)
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Has anyone ever taken a piece of tissue paper, with the heater on, to see if the tissue paper would get sucked onto the grill located in the cabin light rear view mirror assembly?

Does anyone know the p/n for the Interior air temp sensor (B10/4)??
Attached Thumbnails
>9/95 climate control cabin air HEAT problem.-grill-lg.jpg  
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Old 02-14-2010, 05:36 AM   #8 (permalink)
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Bob, do you know if a SDS can tell if my my Interior air temp sensor (B10/4) is functioning or not??
I know for a fact that all it can do is read a fault code in this regard. You can do that without SDS as shown on page 91 of this code manual: http://www.benzworld.org/forums/r129...l?#post2342164.
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Old 02-14-2010, 10:23 AM   #9 (permalink)
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I know for a fact that all it can do is read a fault code in this regard. You can do that without SDS as shown on page 91 of this code manual: http://www.benzworld.org/forums/r129...l?#post2342164.
Thanks for reminding me that there are other diagnosics available within that document. It looks like I will be able to determine if my so called problem exists by using the following info. from page 91-92.

A/C Self Diagnostic Systems

Fault Diagnosis
1. IGNITION : Position 1
2. Temperature selector wheel : "LO"
3. Within 20 seconds press the REST and DEFROST buttons simultaneously for more than 5 seconds.
4. The LED in the RECIRCULATE button flashes and "dI A" appears on the display.
5. Press the AUTO button until all DTC's are displayed and recorded.
6. The current faults are displayed first, then the intermittent faults. "END'" is displayed when all codes have been displayed.
7. To erase codes press AUTO again, "DEL" will be displayed. Press v and ^ simultaneously for more than 5 seconds. The display will then show "---". Press AUTO to cancel the erase.
8. IGNITION : OFF to end the test program.

FAULT CODES - 129 Chassis from 9/95 DTC Readout Description

026 CAN Bus Communication
226 In-Car Air Temperature Sensor (B10/4)
227 Outside Air Temperature Sensor (B14)
228 Heater Core Temperature Sensor (B10/2)
230 Evaporator Temperature Sensor (B10/6)
231 Engine Coolant Temperature Sensor (B11/4)
232 Refrigerant Pressure Sensor (B12)
233 Refrigerant Temperature Sensor (B12/1)
241 Refrigerant Level
416 Coolant Circulation Pump (A31m1)
417 Automatic A/C Monovalve (Y19)
419 A/C Compressor Electromagnetic Clutch (A9k1)
420 Closed (Idle) Throttle Speed Increase
421 Auxiliary Fan Control Module (N65/1)
422 Serial Interface Connection (K1) to Instrument Cluster (IC)
423 Switchover Valve Block (15 connection multiplex) (Y11)
459 Serial Interface Connection (K2) to Instrument Cluster (IC)
Attached Files
File Type: pdf Climate Control DTC's from 9-95.pdf (19.7 KB, 497 views)

Last edited by lynns; 02-22-2011 at 02:50 AM.
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Old 02-14-2010, 05:04 PM   #10 (permalink)
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Date registered: Jul 2006
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Quote:
Originally Posted by lynns View Post
Thanks for reminding me that there are other diagnosics available within that document. It looks like I will be able to determine if my so called problem exists by using the following info. from page 91-92.

A/C Self Diagnostic Systems

Fault Diagnosis
1. IGNITION : Position 1
2. Temperature selector wheel : "LO"
3. Within 20 seconds press the REST and DEFROST buttons simultaneously for more than 5 seconds.
4. The LED in the RECIRCULATE button flashes and "dI A" appears on the display.
5. Press the AUTO button until all DTC's are displayed and recorded.
6. The current faults are displayed first, then the intermittent faults. "END'" is displayed when all codes have been displayed.
7. To erase codes press AUTO again, "dEL" will be displayed. Press v and ^ simultaneously for more than 5 seconds. The display will then show "---". Press AUTO to cancel the erase.
8. IGNITION : OFF to end the test program.

FAULT CODES - 129 Chassis from 9/95 DTC Readout Description

026 CAN Bus Communication
226 In-Car Air Temperature Sensor (B10/4)
227 Outside Air Temperature Sensor (B14)
228 Heater Core Temperature Sensor (B10/2)
230 Evaporator Temperature Sensor (B10/6)
231 Engine Coolant Temperature Sensor (B11/4)
232 Refrigerant Pressure Sensor (B12)
233 Refrigerant Temperature Sensor (B12/1)
241 Refrigerant Level
416 Coolant Circulation Pump (A31m1)
417 Automatic A/C Monovalve (Y19)
419 A/C Compressor Electromagnetic Clutch (A9k1)
420 Closed (Idle) Throttle Speed Increase
421 Auxiliary Fan Control Module (N65/1)
422 Serial Interface Connection (K1) to Instrument Cluster (IC)
423 Switchover Valve Block (15 connection multiplex) (Y11)
459 Serial Interface Connection (K2) to Instrument Cluster (IC)
The above information worked great. I did have DTC's stored.

They were:
416 Coolant Circulation Pump (A31m1)
417 Automatic A/C Monovalve (Y19)
419 A/C Compressor Electromagnetic Clutch (A9k1)

So I erased them. Drove the car up and down the freeway changing the Climate Control from 82 to 68 degrees F with and outside temp of 79 F in Southern California. I then ran the above A/C Self Diagnostic and found NO Diagnostic Trouble Codes. So I can only assume that what I noticed the other day was a fluke or I need to keep my eye on the A/C Monovalve (Y19).

Monovalve's are known to stick and sometimes a gentle tap with a hammer can free them up. On the R107 chassis you can rebuild them but it looks like the R129 requires a whole unit to be R&R'd. See the above picture.

Last edited by lynns; 03-12-2010 at 12:39 AM.
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