Cleaning the W210 Heater Control Valve
 

I've read some stuff, watched a video on cleaning the W210 heater control valve (the duovalve). My 99 E300 has 154k miles on it. According to the PO, several years ago he took it apart, cleaned it, and it's been fine since. Over my couple of months of ownership, it's acted up a few times (heat out the left vent) but whacking it a few times has helped.

Those of you who've been down this road....does cleaning tend to buy you a few years and can you just go on doing this indefinitely? Or, when it starts to clog like this, is it nearing the end of it's usable life and requiring more frequent attention?

I don't want to be constantly hassling with it....I'd sooner just buy a new one, but of course they're pretty pricey.

Thanks.

I reckon' you haven't read this:

http://www.peachparts.com/shopforum/tech-help/242566-how-i-fixed-my-duovalve-w210-got-my-heat-back-saved-myself-$250.html

I did the repair 5 years ago and it's still performing perfectly.

That is a good writeup Evan, I did this to mine and it was very helpful.

I do have one thing to add to this.

Tie a string to the little bails before popping them loose. If you are not careful you can dislodge it totally. It will inevitably fall down below the control box into the darkest depths.

I had to completely disassemble the control box and remove it to retrieve the clip. This was like doing brain surgery on the car. I had to unplug and remove all the modules then find the 4 screws that held the upper half onto the lower half of the box. Only then could I use my "magic fingers" tool to fish it out.

Total time spent on mono valve, about 20 minutes.
Total time spent finding the clip after losing it when putting the valve back together, 4 hours.

One thing to check before taking the valve apart. As my wife says, don't go borrowing trouble.

Put the system in EC mode (no cooling) and go for a drive when it is mild outside.

Go into the diagnostic mode on the AC panel. Hold in REST for 5 seconds or until it changes to a set of numbers.

The parameter is on the left and the argument on the right. Use the AUTO buttons to step through the list.

Look at parameter 02, this is the outside air intake temperature.

Compare them to 03 and 04, these are the left and right heat core temperatures.

If 03 or 04 is greater than 02, your valve is leaking, that is the only way the heat core can be warmer than the air ahead of it.

If the temperatures are comparable the valve is not leaking.

Thanks. Yeah, losing little parts is my biggest concern.

Depends on how far its gone. It doesn't hurt to try and repair it before shelling out the cash for a new one.

Some are successful, some aren't.