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I have a 2008 S550 and my heat is not working. I have the 273 engine which has no Heater Control Valve the 275 & 278 have that valve. Does anyone have any suggestions on my problem. The blower works but just blows cold air, I have check my antifreeze and it is full. I am hoping I don't have to go to the dealer to get fixed.
 

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W164 GL450, W221 S550, R230 SL600TT, R170 SLK230, W140 S500, More
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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 and disconnect the old Valve/coolant clamps.

**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 lose 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.
A shop would probably charge you $400
The valve also known as the Heater Valve, should be a 230 830 00 84 and they are $63 on Amazon.
 

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Discussion Starter #3
They told me at the dealership that that stock numbers fits the 275 and 278 engines and seeing I have the 273 engine that will not work. I appreciate if you can tell me that it would work in the 273 engine. Thanks
 

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That other part is for the R230 SLs, sorry.
FCPeuro says that for the 2008 S550 it is a
Mercedes HVAC Heater Control Valve - Genuine Mercedes 2722000031
They have notes on their website. The cost is $104
 

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'71 Pinto
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Definitive answer, pull codes using Xentry/DAS (MB diagnostics). EPC shows no shutoff valve (170 in diagram) for 2008, check coolant circulation pump (10) part 2218350164 – pumps engine coolant through heater core.
 

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W164 GL450, W221 S550, R230 SL600TT, R170 SLK230, W140 S500, More
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I could be wrong, but Rockauto sells an "electric heater valve" for 2008 S550, the part number is
GATES EHV113 {#2722000031, 68013952AA} Electric Heater Control Valve

specifically for cars made on Oct. 21, 2007 & Older. A VIN check will say the MFG date of your car...
 
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