2012 S550 4matic heater is not working. I already replaced the heater control valve and checked fuses 40 50 and 54. Any help is appreciated.

 

That is unusual. Most of the time it is the heater control valve. Mine was replaced at about 65K miles on a 2007 W221. Did you replace the valve? If yes, did you use a Chinese knock off part? We have heard of the cheaper knock off part being a source of problems. I used a Mercedes part. It was not expensive.

Do you have a scanner? Do you have any codes? If you have no codes, I would bet a donut you have a bad valve, new or not. And I remember Winter weather with no heat was not a picnic at all.

Keep us posted.

 

Thanks vettebk,
Yes, I did replace the valve with a non Mercedes part. So I have ordered a genuine Mercedes valve. Hopefully that will be the fix. I have a icarsoft MBII scanner and car is throwing no codes.
Luckily I have other vehicles so the car hasn't been used since the weather turned cold.
Thanks so much for the help,
Rick

 

Keep us posted. If it is as simple as replacing it with an OEM part; it will be a small lesson. I hope it works and you can return the knock-off part.

It may not be fair to blame the poor quality on the off-shore manufacturer; but when specs are driven by costs, only the purchaser is harmed. Just my two cents.

 

You can use MBII and read the value of heater control valve: there are two control valve controled by ECU ME9.7 and the other heater control valve controlet by Air Condition control module, change temperature seeting from low to hight to see tha valve change state or not.

 

Thank you Minh, I will give that a try.

 

Thanks for the help. I replaced the aftermarket heater control valve with genuine Mercedes valve and so far all is good. The heater is working again!

 

I have heard of several reports of non-OEM valves that were plumbed backwards!!!! Again, it may not be fair to blame the off-shore manufacturer; but I have never had an OEM part cause such a problem. I hope you can get your money back for the part. If not, this was a cheap lesson.

I have also seen a Chinese part in a box that was labelled made in Germany. The box was made in Germany but not the part. I have also seen Chinese parts like water pumps with no internal gear lubricant; just assembled dry. Such parts fail within 12 months like clockwork. Most of this is because the part was made on a low budget with no or poor specs.

My rule is no Chinese parts ever.