viren.89

As the title suggests.

The front A/C is blowing cool air whilst the rear is blowing hot air.

I've tried manually lowering the temps down to all the way to "low"

I've tried leaving it on "Auto" and no avail ?

Anyone knows what the hell is going on ?

I've tried turning off and starting my car again and still nothing.

This is so stupid

viren.89

Never mind- just found out that there is DTB on this.

DTB P-B-83.20/72

Rallyboy383

I just replaced my heater control valve this past weekend. I used a write-up on this site. Make sure to order some new clips for the cowl because they will probably break. It took me about three hours going slow.

efiftyfizzle

It's your heater core valve. There is a sticky DIY for it in the W211 E Class forum.

viren.89

This is nonsense.

I called the dealer and first of all they didn't know what a DTB is and then second they said

they would have to diagnose before replacing anything and they have no service bulletin for this issue.

Is this what you guys used ? Is the part number and everything correct?

https://mbworld.org/forums/e-class-w...rol-valve.html

efiftyfizzle

Yup, you can get it at some of these online parts stores for like 30-40 bucks

Forrest Gump 9

May want to check your freon level first. I had the same problem on my car and the freon was low.

kponti

Even in the unlikely event your freon level is low, with rear hot, front cold (or cool'ish), you should change out your heater valve anyway (~$50 and a couple of hours).
Most likely you will have driver side warm and passenger cool if freon levels are to blame

HeissRod

Isn't it the other way around?

viren.89

Front -all the vents blow cool air and rear all the vents blow hot- it isn't warm , it's hot lol

efiftyfizzle

That's most likely the cause of the heater changeover valve being bad... if freon was low, it just wouldn't be as cold, but when the air is blowing hot, then follow that DIY and get it changed.

Just a little tip... let the car cool down for a while before changing it. When you're pulling the old one out, coolant will come out and it'll be hot if your car hasn't sat for a while.

aespeedy47

yup i just changed my heater control valve and it took me about an hour. also you need to take out the whole wiper unit (3 bolts) and that will give you all the room you need. just order it as a kit off of ebay like i did and it will come with the clips for the cowl. i think it costed me 60.

Quicksilv3r

I had this problem (along with a few phantom OBC failure messages for various components) and had the dealer replace the main battery. I never experienced any of it again.

kponti

Maybe so , I haven't had mine lose freon before. However from what I've read it is usually the driver side that gets hot with low freon

viren.89

Just as a closure if anyone comes searching for this thread.

I used this thread to replace my HVAC valve.

https://mbworld.org/forums/e-class-w...rol-valve.html

viren.89

Although a car of this stature the A/C could've been better. As in the air even at the lowest setting isn't that cold.


During the wiper assembly removal -I accidentally dropped the socket and bolt inside and now it's lost forever

Oh and you'd NEED patience cuz the plastic trim to get it off and back on is not for the faint of heart lol

Denroll

There's a "hot climate" setting that can be accessed in STAR. I'm going to do mine whenever I can get it on one. Supposedly makes the A/C work better.

viren.89

Please let us know if that works.

HeissRod

Subscribed

Denroll

Also, if you're replacing the heater control valve, having a pair of hose clamp pliers might make life easier for you. The one spring-style hose clamp that needs to be removed was a real pain in the bunghole as the clamp part was rotated towards the firewall. This one clamp took about 30 minutes to remove and resulted in the deployment of many F-bombs.



I also had a spring puller in my toolbox which made short work of those latches. There is one that is waaaaaay down there. Spring puller is basically a hook like the bent coat hanger, but it's stiffer and has a handle.

HeissRod

lol @ deployment

Monsr

layzie12g

I did the heater control valve and it did not fix it. I had to replace a chip on the circuit board on the front SAM. I have the chips in stock if you need one, or you can replace the entire front SAM.

jrocco1971

My 2005 E500 suddenly has this problem — out of f-ing nowhere. Rear a/c was ice cold last night. Today it’s blowing 130 degree heat while the front is blowing 62 degrees. Utterly ludicrous. So it might be an electrical problem now? How can I tell the difference and make sure I’m doing the correct job before I start tearing the car apart?

radride

I just had this same issue. It was the heater control valve. If you have access to the STAR and scan the car, you’ll have a fault on the heater control valve.

R.K.