Rear Aircon Hot Hot Hot!

[Vilus]

Hey Guys, Took the E55 for a 100 mile blast in the heat yesterday. When I arrived I panicked to find a trail of wet patches down the road where I stopped and water dribbling out from the gearbox/bulkhead area. Thought initially it was gearbox radiator, but was clean pure water. Thought maybe as it was humid it was hopefully condensation and later in the day made the return trip. Driving down the M2 I became aware of a very warm left arm. The dash was blasting icy cool air, but the rear vents although both set to Lo were blowing really hot air.

Did a few searches, and it would seem a common enough problem, due to a faulty heater control valve in the bulkhead. However took it to two local Merc Indies. First one said it could not be the valve, and wanted to make his own diagnosis. Took it to the second one who serviced my car last year (30 years Main dealer experience!), he stated he had never come across this problem before, and that the Valve only controls left/right flow to the heater core. He is saying could only be actuator motor in vent system and again wants me to bring it in later this week to put on Star. Since the advice in the various forums seems consistent, I am tempted to just go ahead and get the valve changed, but am conflicted by the advice from my Indie.

It is a w211, with 4 zone climate control. Any advice would be welcome, thanks.

 

[WG M-B]

In my experience it's the valve
Changed one last week for the same issue on a w211. The w220 has a separate valve that causes the problem

 

[AndyPCD]

Have to agree i would be looking at the valve as well. Very common problem on the 211

Bit of a nightmare to change due to being under the brake reservoir

 

[Ginger55k]

I have the same on my 55, sometimes if I cycle the rear heater controls to max heat and then back to min it cools down, other times it stays hot, have to agree with WG M-B its the valve, and its a pig of a job to get to it on the 55.

Its on my list of to do.

ginge

 

[Ginger55k]

Have to agree i would be looking at the valve as well. Very common problem on the 211

Bit of a nightmare to change due to being under the brake reservoir

just beat me to it

 

[Major774]

Had this problem on my car, replaced the duo valve myself... nightmare of a job haha.

 

[Alps]

my indi changed my valve, if i remember right he loosened the brake resevoir to access it easier, took him about 45 mins.

 

[Vilus]

Replaced the valve today, and hey presto all sorted. Realised that there was still some warm air entering the front vents, but that Aircon was cooling it. That was why I was getting loads of condensation pouring out from the aircon/heater matrix. Took about two hours of fiddling, but it's ice cold now.

 

[V8 Supercharger]

In my experience it's the valve
Changed one last week for the same issue on a w211. The w220 has a separate valve that causes the problem

Sorry, but which valve is it on the W220? And where is it located if different to the W211?

Mines a 2004 W220 S55 and the centre arm rest area is always boiling hot, and the rear vents are usually blowing out hot air regardless of what the front is set to. Never tried the rear air con.

Im pretty sure thats why the phone in the armrest got knackered, because of all the heat. And when i say heat, i mean after an hours drive you cannot hold the phone in your hand

Iv always thought this was the gearbox causing this much heat???

 

[Vilus]

the climate control on the S class looks a lot more complicated than my E class. I'm sure your problems will be down to a faulty valve though, usually located in or near the bulkhead.


This climate control link on this page might be of help.

Welcome to the S-Class

 

[V8 Supercharger]

Switched the rear AC on last night, set it to LOW . . . . . nearly burned my face off.

Somethings defo not rite in here.

 

[WG M-B]

From memory the valve is under the drivers side front wheel arch liner on the w220. This is the hot water shut off valve

 

[mikeyg1959]

Hi
I had exactly the same problem and paid over £400 to get it fixed based on info on this forum and the issue remained with the heater control valve replaced. Still scalding hot air blasting from the rear vents regardless of settings - front working as it should. So back to drawing board i'm afraid. Be careful before parting with your cash.
There is something else afoot with my W220 S320 51 plate me thinks.
Mike

 

[mikeyg1959]

Any other suggestions would be welcome please.
Mike