g2005clk320

Can anyone please share any insight on this issue and how to fix? I have a 2005 Mercedes CLK 320 cab that won't blow heat on the passenger side. It seems to all go to the drivers side. AC is not an issue, as it works fine on both side. There is no air coming out at all on the passenger side when set to heat. It all comes out on the drivers side and is really hot on my feet.

Any help would be appreciated. Thanks.

Glyn M Ruck

Well the hot water is obviously getting to the heater radiator or you would have no heat so it can't be the secondary coolant pump or a stuck valve.

The most likely cause is a failed stepper motor on one of the distribution flaps or a broken stepper motor arm. Your car however has the new arms that are not supposed to break.

Do you hear any clicking noises from behind the dash when you first switch on which would be indicative of a broken arm.

g2005clk320

Glyn,

Thanks for the response. No, I don't hear any clicking sounds. I occassionally do hear a squeaking noise that adjusts with the hvac fan speed on heat or a/c and which is coming from behind the glove box.

I just went out to observe it again. If I have it off auto, max fan speed, lowest temps for driver and passenger, then I get air on both sides. If I then move the temperatures up, the air flow eventually cuts off on the passenger side as the temperature approaches max.

I'm wondering if it's the changeover valve (not sure what this does but apparantely a common problem) or if it's a motor controlling a flap that adjusts airflow to driver vs. passenger. Maybe this flap is stuck open to driver.

-Greg

Glyn M Ruck

OK - some research - I'm sorry I'm still getting used to the CLK differences from my previous Benz models.

Wierd steering of air to wrong vents or vents inoperative is frequently broken stepper motor arm or stepper motor failure. Resulting in a stuck or inoperative flap.

Cold air to front & hot air to rear. Is usually the hot water changeover valve or Duovalve as it is commonly known in MB speak. I don't think this applies to your year.

Now this is the classic - don't be fooled by an aircon that apparently works. Hot air one side cold the other to the floor can be a reaction to low refrigerant level & is designed this way for S Class & E Class.

Now the CLK is a bit of a hybrid. But on the 320 is a modified W203 unit - I have not checked newer models.

50 & 60 are the front floor air guides. Your problem is almost certainly a stuck flap or a misbehaving or failed coded stepper motor or something broken or damaged in the footwell operating linkage 180 group in the diagram.





Before you go diving into the dash try a system reset here:

https://mbworld.org/forums/c-class-w...nic+easter+egg

This will reset all the stepper motors & the system to default.

Good luck!

jhk777

Same problem with my 2007 C280. I tried the Climatronic reset technique by holding down "defrost" and "recirc" buttons together. During the alternating flashing lights I can feel a transient (2 seconds) amount of hot air blowing from the all the passenger side vents ( windshield, center, and floor vents) then no air flow again. The heat setting was on max. A/C works fine--plenty of cold air from all vents both sides and volume feels equal both right and left. I can see the passenger and driver side floor vent stepper linkages moving similarly when changing temperature setting from A/C to heat. Is there a separate, single air flap/stepper motor between the blower and all the passenger side vents?

Any help/advice appreciated.