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Discussion Starter #1
We here got a cold spell and I turned the dial for heat.
Now, it continues to blow hot air even though it set to the blue side. Is there a valve that is stuck and what do I need to fix it.
Please help.
Thanks
 

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There is an electric motor that controls the blend air. It may have a problem, which occasionally happens. Is there any strange noises coming from the dash? If there is a problem with the stepper motor, it will throw a trouble code in the climate control unit. But I don't believe a generic OBDII scan tool can retrieve that code. You might have to find someone with a professional scan tool to get that code.
 

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Discussion Starter #3
Regarding the climate control

There is no noise coming from the dash.
Last week, we had a cold spell here in San Antonio and
I turned up the heat and then when I switched it back
cold side, it continued to blow from hot to warm air, this is the outside air. The outside temperature was cool around 67F. This started all of a sudden.
Also, when I turned on the A/C, air got just a bit cooler
but not cold. Yes, you were right, I could not get any fault code with the OBDII scanner.
When I talked to the parts guy, he told me that the climate control on the console is a special order but
they stock two motors.
Also, when I turn the temperature knob to cool side and it clicks, I hear something switching through the center vent.
any ideas? and also how to replace this motor and which one? pl let me know.
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I need to make sure I'm telling you the correct information. What year is your truck? Because from 2001 on, they have a totally different climate control system than the older ones.
 

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Discussion Starter #6
Problem resolved with ML55

It was the motor that controls the hot and col air mixture
and it require taking out the dash.
The motor is visible if one takes out the instrument cluster, steering, combination switch and also small
panels on either side of the steering.
I also replaced the other motor that controls the vent flaps. Also, replaced all the bulbs in the cluster from autohausaz.com.
I did buy the motors from the MB dealer, want to use only factory, cost was like $108 and $41.
took me like 6 hours.
Barry
 
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