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95 S500, 07 S550 AMG
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791 Posts
Discussion Starter #1
If you have an issue where your car stopped blowing warm or hot air (no matter what temperature or vents you select),
you most likely have the CHANGE OVER VALVE going bad.

*** Understand this problem is something DAS/STAR is not able to diagnose and scan as faulty.

This is only for vehicles with "No Heat" issue. In this condition, A/C-cold air and outside air work as they should. Problem is noted when heat fails to deliver on cold days/morning/evening when requested by the driver/passenger. Operator selects heat but gets whatever temperature air is outside.


The change over valve, controls how much (hot) coolant should go through the heater core. When this goes bad, the coolant going to the heater core is blocked, thus not heating up the heater core = no heat.

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The part is located under the windshield wipers, behind the firewall cover (look at pics)

Firewall cover pulls up after removing the engine compartment rubber seal (very easy to do)

Get some hoes clamp pliers (I didn't have one so i used some old pliers that worked with some effort) and disconnect the old Valve/coolant clamps away.

**YOU WILL MOST LIKELY BREAK THE OLD VALVE INLETS. They are easy to break but the good news is you don't need the old valve anyway. If they break, make sure you don't have any plastic pieces inside the tubes.

You will loose some coolant. I lost and refilled less than a gallon 50/50 antifreeze.

You might have to fill the tank up more than once as the thermostat opens up.

If you have any questions let me know.
OEM part cost me $65 online

Mercedes R230 W216 W221 CL550 CL600 CL63 Genuine Heater Control Valve | eBay

GOOD Luck (You saved yourself $400+ dollars)
 

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2004 S430, 2007 S550
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134 Posts
If your acquire a 2007-2009 you should replace this part(A230 830 0084 - $53.64 on ebay shipped free) immediately. The top piece of this valve broke off leaving me stranded and it is a very easy fix.
 

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1991 300SE
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49 Posts
Arlind86, Thanks for posting these instructions. I have a 2008 S550 that I recently bought, this was the first time I drove it in the winter cold weather, the heat was always working but after driving to the store I parked the car in the parking lot and the heat suddenly stop working, it was only blowing cold air. Is it possible that my Heater Control Solenoid Valve is defective and is this a easy repair job as you described, any help would be appreciated, thanks
 

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Registered
2004 S430, 2007 S550
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134 Posts
Arlind86, Thanks for posting these instructions. I have a 2008 S550 that I recently bought, this was the first time I drove it in the winter cold weather, the heat was always working but after driving to the store I parked the car in the parking lot and the heat suddenly stop working, it was only blowing cold air. Is it possible that my Heater Control Solenoid Valve is defective and is this a easy repair job as you described, any help would be appreciated, thanks
See my post above yours.
 

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1991 300SE
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49 Posts
Thanks for the suggestion, I will replace it very soon. It actually started blowing hot air again but obviously going bad. It must have been a very frightening experience you had when you got stranded on the highway, plus the inconvenience
 

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If you don't get an answer here, try the W222 forum.
Any info on the w222 yet. Same problem first dealer charged me for a software update. Didn’t work. Then charged me for problem being low coolant but not low enough for low coolant light to come in. Also didn’t work. Usually stops working when I turn ac on and then try to turn heat back on
 
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