[Doni]

I've got a 2012 S550 with no heat....in Chicago! Today I replaced the heater valve under the hood as per recommendations here but still no heat. I noticed the heater valve has an electrical connection so I assume there's a relay or fuse somewhere that powers the valve.

If so, WHERE IS IT?? Or is there a secondary/auxiliary coolant pump that drives the heater valve as in the W124? If so, where is THAT? I just checked to see if any of the hoses connected to the heater valve were warm/hot (the car's at operating temp) and none of them are. In fact, all 4 hoses are cold.

I've looked at as many fuse diagrams as I can find and can't determine which fuse or relay controls the valve, if any.

Can you guys help? A car with no heat is pretty much useless in Chicago this time of year! THANKS IN ADVANCE FOR ANY HELP!!!

 

[konigstiger]

There’s a coolant circulation pump in close proximity to water valve (part 2218350164). If this seems fine best to have someone pull fault codes rather than chase parts.

 

[s550hollywood]

If you have a 2012 S550, this video shows what to replace if theres not heat but your AC still blows. I have a 2013 and did this same fix for no heat and it fixed it. Cost me $60 for the part and 30 minutes. Heres two videos of the same fix, both are helpful.

 

[Doni]

I already did the heater valve a couple days ago. I finally had to surrender and take the car to the dealer. It turns out there was a hose from the secondary pump to the cylinder head that had somehow collapsed and was not allowing coolant to flow.

A $350 bill (incl inspection) for a $35 part. Oh, well. At least I have heat now.

 

[LuauLounge]

Just had my heater valve replaced at my local Indy. $182 out the door, in California no less.

 

[EAK]

If you have a 2012 S550, this video shows what to replace if theres not heat but your AC still blows. I have a 2013 and did this same fix for no heat and it fixed it. Cost me $60 for the part and 30 minutes. Heres two videos of the same fix, both are helpful.

Thank you for all the help; I used these videos, replaced the heater control valve on my 2013 S550 W221 M278 and it works PERFECTLY. Cost: $47 from Amazon. Thanks again! Saved at least $600 at the dealership. Mileage on car 98K. Known defect at 100K. Again, very predictable, and very thankful for the help.

 

[s550hollywood]

Thank you for all the help; I used these videos, replaced the heater control valve on my 2013 S550 W221 M278 and it works PERFECTLY. Cost: $47 from Amazon. Thanks again! Saved at least $600 at the dealership. Mileage on car 98K. Known defect at 100K. Again, very predictable, and very thankful for the help.

Mine went bad at 68,000 right after I bought the car from a dealership so they can go bad before 100K. This tool is a must have for this repair.

 

[s550hollywood]

Mine went bad at 68,000 right after I bought the car from a dealership so they can go bad before 100K. This tool is a must have for this repair.

Thats ODD, I cant post a picture of the pliers, but they are called hose clamp pliers that have a long cable on them and free up your hands while they hold the clamp open.

 

[EAK]

Mine went bad at 68,000 right after I bought the car from a dealership so they can go bad before 100K. This tool is a must have for this repair.

Also

Thats ODD, I cant post a picture of the pliers, but they are called hose clamp pliers that have a long cable on them and free up your hands while they hold the clamp open.

I did use hose clamp pliers with the extension as I would have not been able to do otherwise; I picked that up from the video, and it was a deal breaker for me, in that, the clamps from the factory were not facing forward but facing backwards towards the cockpit. I did remove the rubber stripping and that little gate behind the engine to get my access. I did not remove the windshield wipers.

 

[s550hollywood]

Also

I did use hose clamp pliers with the extension as I would have not been able to do otherwise; I picked that up from the video, and it was a deal breaker for me, in that, the clamps from the factory were not facing forward but facing backwards towards the cockpit. I did remove the rubber stripping and that little gate behind the engine to get my access. I did not remove the windshield wipers.

That really sucks, for me the clamps were facing to where I could easily clamp them but a lot of people try doing it with regular pliers and thats just too much work. I bought my clamp pliers from Autozone and after this one repair, they would not hold anymore so they are garbage. Next time I'll buy the SnapOn ones as they are designed a bit different as to not fail. Harbor Freight also has some really good long reach ones but none with the cable.

 

[Shadly1]

I picked up this set specifically for this job. It would have sucked without it. I don't despise constant tension spring clamps as much anymore.

3Pcs Hose Clamp Pliers,Remover Kit with Long Reach Wire Spring Hose Clamp Pliers