W219/211 DUO HEATER VALVE REPLACEMENT

[MartiniNight]

Hello does anyone changed the Duo Heater Valve on a w219?
Uk RHD?
How hard it is?
I've read RHD cars the duo valve is unaccesible because is buried under the master cylinder or something?
My symptoms are:
My passenger side vents blows ice cold and driver side vents blows warm air.
All vents set on cold..
Same with the rear vents..left vent blows ice cold right vent blows warm
(W219 2010 cdi)

 

[Teego]

I recently had a problem with the duo valve on my W219. Only gave cold air. It sits on the driver side bulkhead under the brake master cylinder. It's tight.
So I started with the simple things first and assumed I got cold air because the valve was stuck shut. A combination of tapping the valve body and toggling the heater from min to max eventually restored flow through the system. I had to be patient and do the job slowly and carefully until I got a result.
The system has worked well since.

 

[Smiley]

Correct access is difficult on rhd cars. IIRC the MB instructions are to remove the brake booster assy which makes it a big job. It can be done without removing the booster but unlikely if you are doing the job for the first time. I'm not sure that you'd get your symptoms from a failed duo valve - I got no hot air at all when mine failed.

 

[MartiniNight]

Correct access is difficult on rhd cars. IIRC the MB instructions are to remove the brake booster assy which makes it a big job. It can be done without removing the booster but unlikely if you are doing the job for the first time. I'm not sure that you'd get your symptoms from a failed duo valve - I got no hot air at all when mine failed.

Hi thanks for reply.
My symptoms are;
- left side vents are blowing ice cold and right side blow warm air.
All vents settings on cold.
-also vents also blow hot if i want to,means something is still allow hot air to pass..but the ones on the right side just don't blow as cold as it should when i select cold.
You think this is the duo valve or just needs ac regass?

 

[Teego]

If all vents blow hot your duo valve is opening. Maybe one valve is not closing properly

 

[MartiniNight]

If all vents blow hot your duo valve is opening. Maybe one valve is not closing properly

Which valve may not closing properly? Duo valve?

 

[Teego]

Which valve may not closing properly? Duo valve?

Duo

 

[andy27168]

Hi,
Just for complete info, the duo valve, without any input from external sources eg. control unit or being jammed by sludge and dirt in the coolant, the valve will be open so default blows hot air.

 

[Smiley]

Hi,
Just for complete info, the duo valve, without any input from external sources eg. control unit or being jammed by sludge and dirt in the coolant, the valve will be open so default blows hot air.

That was not my experience. When mine failed I got only cold air in the cabin. After it was replaced I cut the old one apart just out of interest - expecting to find the operating valve covered in rust and jammed up - but in fact it was all clean and there was no visible reason why it should have failed......except for the fact that it is obviously built down to a cost and is a tiny flimsy little motor driving a very simple valve mechanism all in a sealed plastic "box". I bet the cost from the far east manufacturer is no more than a couple of pounds. Surprising that they last as long as they do.
If the OP has hot and cold air in the car I would be checking the other components and how much gas is in the system before replacing the duo valve.

 

[MartiniNight]

I recently had a problem with the duo valve on my W219. Only gave cold air. It sits on the driver side bulkhead under the brake master cylinder. It's tight.
So I started with the simple things first and assumed I got cold air because the valve was stuck shut. A combination of tapping the valve body and toggling the heater from min to max eventually restored flow through the system. I had to be patient and do the job slowly and carefully until I got a result.
The system has worked well since.

Hello Teego, im about to try and tap the valve to see if it moves. How did you tapped it ? Slow tapping or hard tapping? Cheers

I recently had a problem with the duo valve on my W219. Only gave cold air. It sits on the driver side bulkhead under the brake master cylinder. It's tight.
So I started with the simple things first and assumed I got cold air because the valve was stuck shut. A combination of tapping the valve body and toggling the heater from min to max eventually restored flow through the system. I had to be patient and do the job slowly and carefully until I got a result.
The system has worked well since.

How did you tapped it? Slow or hard tapping? Cheers