DIY: Installing a new Changeover/Heater Control Valve
Out Of Control!!
Joined: Jul 2003
Posts: 15,901
Likes: 4,630
From: North Scottsdale, AZ
'71 Pinto
Hi,
I have another problem (posted on another topic aswell), but i think it could be linked to this problem.
My problem is that i have a similar problem, but not between front and rear but between left and right.
On the left side i have a temp differance. The maximum differance is at the highest when you put both sides on "LO" and i think it's +/- 5 degrees celcius differance). It's not hot air comming out, but it feels like there is no airco comming out. The icey feeling like airco is missing on the left (drivers) side. Right side is fine. And the problem is on left side all vents, not only centre console.
I've checked the sun sensor and it seems to act weird, but after disconnecting it's doenst fix my problem, so that couldn't be it.
Someone adviced to change the 2 inside temp sensors, but i'm not sure how and if this is possible because i think it are 2 different types of sensors.
Can somebody please help me?
I have another problem (posted on another topic aswell), but i think it could be linked to this problem.
My problem is that i have a similar problem, but not between front and rear but between left and right.
On the left side i have a temp differance. The maximum differance is at the highest when you put both sides on "LO" and i think it's +/- 5 degrees celcius differance). It's not hot air comming out, but it feels like there is no airco comming out. The icey feeling like airco is missing on the left (drivers) side. Right side is fine. And the problem is on left side all vents, not only centre console.
I've checked the sun sensor and it seems to act weird, but after disconnecting it's doenst fix my problem, so that couldn't be it.
Someone adviced to change the 2 inside temp sensors, but i'm not sure how and if this is possible because i think it are 2 different types of sensors.
Can somebody please help me?
Out Of Control!!
Joined: Jul 2003
Posts: 15,901
Likes: 4,630
From: North Scottsdale, AZ
'71 Pinto
Perhaps you should have dealer or independent check refrigerant and retrieve any fault code(s) that may be stored with SDS for proper diagnose.
Junior Member
Joined: Mar 2008
Posts: 18
Likes: 0
From: Austin, TX USA
04 E320
Thanks for a terrific set of DIY instructions. I do have one question though. When you remove the wiper arms are the posts to which they are attached keyed in some way, so as to keep you from putting them back on the wrong way? I've never pulled these off my 04 and I want to make sure I put them back on right when I replace this valve. It was periodically driving me nuts blasting air from hell during the heat of the summer.... then it just stopped doing that to my personal delight, until this morning after a cold front had come in... and I had no heat on the way to work this morning....LOL. So it's time to finally break down and do this. Thanks again for the great write up and pictures.
Last edited by Zaphodsplanet; Sep 27, 2010 at 02:49 PM. Reason: typo
Banned
Joined: Oct 2005
Posts: 4,957
Likes: 1,640
The wiper arms are not keyed, but you may want to note their position so you get them back properly. The post is grooved so they do "engage" into an alignment of sorts. Hope this valve works for you. After I replaced mine I still have the issue and it appears my driver SAM is the culprit here sending an improper signal to the valve. I have to replace the SAM.
Junior Member
Joined: Mar 2008
Posts: 18
Likes: 0
From: Austin, TX USA
04 E320
Thanks Key08. I hope to God it's not the SAM.... I'm not sure what that acronym stands for....LOL. But anything that involves a computer on these cars ends up uber expensive. The valve was acting up off and on all summer.... doing all the things that people had remarked about. And now there's no heat. I'll see if I can find some kind of white marker to put a couple tick marks on the posts to mark them before I pull them all the way off. I don't suspect I'll have time to do this until this weekend. And as I live in Texas it's rarely all that cold. However... if the valve doesn't fix the problem and I run into your same error.... it's time to trade in the car. I still have to replace the gas tank which is $1700. That one still riles me. I've never had a benz with a leaking gas tank.... and I've owned 5 or 6 others. Thanks again for the heads up and I'll post results after I change it out.
jeffrey
jeffrey
Banned
Joined: Oct 2005
Posts: 4,957
Likes: 1,640
I think 99% of the rear heating/cooling problem is this valve and I just happen to be in the 1% where it is the driver SAM that controls the valve not functioning properly. Now that cooler weather is here in Chicago I am not experiencing the problem since it really exacerbates when it is very hot out. Replacing the SAM is a grand from my dealer and I haven't priced it with an independant yet, but I'm in no hurry. The DIY on this valve replacement is very easy and you should have no issue. Sorry about your gas tank. That is nuts.
Junior Member
Joined: Mar 2008
Posts: 18
Likes: 0
From: Austin, TX USA
04 E320
Hey KEY08..... After a little knuckle bashing and scraping.... I got the new valve in and have heat again. Thanks for everyone who posted notes in here.. it was a big help. I can't remember if anyone else commented on this, but when you put the new valve in wait to reattach the hose on the top... it makes it a hell of a lot easier to get the new valve wiggled into place. And as a few others have pointed out... I don't know how in the hell anyone would have managed to change this thing out w/o removing the windshield wiper motor assembly... OMG.
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Banned
Joined: Oct 2005
Posts: 4,957
Likes: 1,640
Yeah, it takes no time to remove the wipers, otherwise you are working almost blind and feeling your way. The only thing I ran into was an inordinate amount of coolant that seemed to keep running out as much as I tried to minimize it. It is an easy DIY if you just take your time and feels good when complete.
Newbie
Joined: Oct 2010
Posts: 1
Likes: 0
'05 e320 4matic
heater control valve replacement!
I'd would just like to offer my thanks to the gentleman who was gracious enough to take the time and effort to post those pics and directions for the replacement of the valve. I would also like to add that removing the wiper assemlby beyond just the wiper arms is not as diffucult as one would think. 2 nuts and one bolt and an modular electrical connection and its removal creates considerably more room to work. The Job took about one and a half hours from start to finish. Special thanks to my wife who held the light and was my advisor during the proceedure. 
Newbie
Joined: Sep 2007
Posts: 12
Likes: 1
E500 with sports package
Update. It seems that when I changed the valve I immediatly started the car to check fo leaks. I did not get heat and concluded that the new valve did not work. Well I took it out on the road and low ane behold the heat worked. THansk for the excellent post and dollars savings. Whole change took about 1 1/2 hours. Saved $250.
Newbie
Joined: Sep 2010
Posts: 1
Likes: 0
From: WIGAN LANCASHIRE UK
ECLASS 270 CDI AVANTGARDE AUTO, OBSID BLACK
27 Nov 2009 UKW211 E200K 1.8K Avantgarde 24th March 2003
heater not working and having found and digested RYDA's article, I went out and bought the part £24.50 inc taxes
Got to the stage of taking out foam padding and realised the valve was not there, found it under the master cylinder
toyed with the idea of taking out the fuse box to get to it, not a good idea.
having only taken off the 2 hoses going into the bulkhead, I managed to wiggle the bugger up onto the top
of the master cylinder, where the change over was simple, then squeezed it back to where it came from.
opened the old part, and yes it had let in fluid and corroded, after 6 1/2 years.
It took 1 hour to strip parts out
2 minutes to find the valve, and 45 frustrating mins to get it out
then only another 35 mins to put everything back.
Last edited by spera; Oct 22, 2010 at 03:18 PM. Reason: misssed word
Junior Member
Joined: Sep 2010
Posts: 20
Likes: 0
From: Pennsylvania
2003 E500
Removal and installation went very well, took about an hour. Many thanks to all who posted, removing the wiper motor assy was especially pertinent.
Curiosity got the better of me, so I popped open the valve:
Curiosity got the better of me, so I popped open the valve:
Newbie
Joined: Nov 2010
Posts: 1
Likes: 0
E320
Success!!!
Thank you, RYDA!!!!
I've never so much as changed my own oil, but successfully performed this DIY with this walk-through by my side. It took me approximately 3 hours with some minor SNAFU's.
~ I had to replace all 4 rivets as I expected. I already had them on hand for the job.
~ My E320 did not have the mystery module, so I didn't need the Torx 25 bit.
~ I broke the air intake on the molding right off. Fixed it with super-glue and electrical tape. Good as new!!!
~ After I had replaced the plastic molding, I discovered I had forgotten to plug the wiper motor electrical wires back in. Off came the molding AGAIN!!! This time I was super careful and saved all 4 rivets.
~ All-in-all it took 3 hours, 1 cigar, 1 beer and $60 to complete this job. If I could do it anyone can.
Thanks again!!!
I've never so much as changed my own oil, but successfully performed this DIY with this walk-through by my side. It took me approximately 3 hours with some minor SNAFU's.
~ I had to replace all 4 rivets as I expected. I already had them on hand for the job.
~ My E320 did not have the mystery module, so I didn't need the Torx 25 bit.
~ I broke the air intake on the molding right off. Fixed it with super-glue and electrical tape. Good as new!!!
~ After I had replaced the plastic molding, I discovered I had forgotten to plug the wiper motor electrical wires back in. Off came the molding AGAIN!!! This time I was super careful and saved all 4 rivets.
~ All-in-all it took 3 hours, 1 cigar, 1 beer and $60 to complete this job. If I could do it anyone can.
Thanks again!!!
Newbie
Joined: Nov 2010
Posts: 5
Likes: 0
From: Orlando Florida
2003 E500
Thanks Ryda and everyone else who added to the post just got done with this job and without this post and all your help I would have ended at the stealership btw taking the wiper arms really gave me the extra clearance thanks!!!!
Newbie
Joined: Nov 2010
Posts: 1
Likes: 0
E 240 W211
Great thread
Hello all, this DIY thread saved me quite some bucks! Just did it in about an hour incl. removing the Wiper assembly. The valve was about € 35:-. MB garage suggested a repaircost of around €1200-1300:-, went on about some valves behind the instrument panel that needed to be replaced as well...they would have to remove the whole glaresheild to do that??! My heating system works fine now having only replaced this one valve.
MBWorld Fanatic!
Joined: May 2003
Posts: 1,100
Likes: 4
From: ChiTown
06 Carrera4
You guys are lucky. I called my local and they told me it's $378 for this part for S500
Does anyone by chance think this part would cause heat to be just warm and not hot?
Does anyone by chance think this part would cause heat to be just warm and not hot?
Last edited by malahhaor; Dec 8, 2010 at 12:14 AM.
Newbie
Joined: Aug 2010
Posts: 4
Likes: 0
From: Chicago, IL
2004 E55 AMG
I had the same issue... Cold air would blow out on HI. It was on/off for a about a week until it the unit finally failed (30-10 F.) Got the part for $40 bucks with my wholesale dealer account. This DIY was a GREAT help for sure, the pics really give you and idea of what your gonna be looking at. Took me about an Hr. I did the job inside a dark lit garage in my building, had my iphone for spot light and music. You will have to remove the wiper assembly to take out the actual part. I recommend you remove the 3 clips first, leave the hose clamp for last and install it first since you get a little play with the hose. This was on a 2004 E55 with 90k
Junior Member
Joined: Oct 2010
Posts: 61
Likes: 0
From: Chicago
E350 Sedan Sport
I've slso got heat problems on my E350, so I bought this part and tried installing it. I got everthing attached, however I could not get the engine bay hose to snap in to the new part (I even tested putting it back into the old part which I was able to do). Has anyone else done this fix to a E350? 
