[Sean Garrity]

Hello, I am new to this "forum" stuff so hear it goes. I have bought a 1999 e300 about 6 months ago and at the time it was warm outside and the airconditioning was doing the blow warm air out of left vent sometimes thing. Through forums and questioning, I eventualy fixed that with a tap to the duovalve. This all after recharging the 134 system and replacing the cracked radiator. So all was well through the spring and summer but now not so. Now I have no heat, none. Just cold ,AC air, blows from whatever vent I select unless I hit the econ button. Hear is what I have done so far; unplugged duovalve, took appart duovalve and cleaned, listened to the external water pump make gurgling sounds when hoses where off, checked power to external pump and duovalve, checked the acc codes and the only onse where for left and right duovalve solenoids. The duovalve is hot on top, when car is at opperating temp, and cold on bottom. The two brass looking plungers in the bottom of duovalve where just sitting there when I took it appart and that seemed odd unless the system is flowing backwards from what I am thinking. The solenoids pushed the shafts down when I had it appart and connected to power and put acc on low. I am confused hear and would appreciate some good advice. Also the acc rest button does nothing, no lite when pressed and does not turn off the ac compressor. Sorry for the long post.

 

[Kajtek1]

From what I know the duovalve is normally open and it takes electric current to close it.
Since you cleaned the valve, I would suspect some kind of control glitch.
Pulling the plug on the valve should have it open all the time.
There is more possibilities, like clogged cores or miss-assembled valve.
Welcome to the forum.

 

[Sean Garrity]

Tank you for your quick response KajteK1. Heater core flows free and you are correct on the the valve, when on heat or unplugged, it is supposed to keep the plungers open so flow would not be interupted and when you turn the acc control to lo it closes those plungers to keep het from the core. I am not 100% on that but I used to be a mechanic so some of this is a bit familiar, just a little confusing on the German vehicles. I love them just don't understand how they work. When I had the valve appart it looked funny, like the brass plugs should be attatched to the plungers and not just sitting there. Unless the flow comes through the heater core and from the bottom of the duovalve? But that would make me think heat would allways be there. If you or anyone might know where I could find a detailed diagram of the duovalve so I could move to the next idea that would be great. Someone posted some camera pics cleaning one in "the stickeys" or somewhere on hear but it looked just like what I had. Sorry it took so long to reply I am working today and will be off tomorrow afternoon to return to working this out. Thanks again.

 

[raMBow]

Not sure what you mean by the brass plugs should be attached to the plungers...

There is a long thin plastic stem and the brass plug as you call it.

Here is what it should NOT look like - this is what we call broken plungers as I just yanked it off not thinking as I had similar problems. I just replaced the duovalve and all was well, other than my wallet.

 

[Sean Garrity]

Thanks raMBow My plastic stems are in tact. My question is are they supposed to be attached or do they slide in and out of the other part freely? Looks like I will try and take out those plungers all together and if I have heat, I'll buy a duovalve. Where did you get yours and how much if you don't mind me asking?

 

[Sean Garrity]

Wow, sorry for all the miss spelled words. I'm not the best speller and combined with lack of sleep, oops. Going to sleep for a bit. It has been a long 30 hour shift. Thanks for the replies.

 

[Kajtek1]

Why would you think about buying new valve before testing it by pulling the plug?
You'd rather spend $200 on part than spend 10 second testing?

 

[Sean Garrity]

Thanks again for the reply kajtek1 but in my first post the first thing I mentioned trying was unplugging the duovalve. I am not trying to spend the money that is why I'm trying this forum. Please do not think I'm trying to be a smart but hear, not the case I really do appreciate the replies and hope to use this forum for my next issue which is my shifting issue but first the heat. Thank you again.

 

[260e crusier]

There should be an arrow on the valve showing the direction of flow. On my monovalve, water flows up from the bottom inlet and pushes the plunger (its free floating, not solidly attached to anything) up to allow heated water to flow FROM the core. If there is voltage at the solenoid, the plunger is forced down cutting off flow. So.......... to test the valve, unplug the solenoid (you should be able to hear/feel something) with key in the "run" position and climate control off. Next, repeat with climate control set on defrost (you should NOT feel or hear anything from the solenoid.

Sounds like your climate control panel (very common problem with the older cars) or the solenoid is bad if you were getting heat on with the AC during the summer.

 

[Kajtek1]

Just cold ,AC air, blows from whatever vent I select unless I hit the econ button. .

I reread it again and BINGO.
You do have a heat, only the AC is not cutting off.
The title is misleading and that what prompted us into wrong direction.
Both our W210 have the clima system going highwire occasionally. It takes setting it to like 80F before the AC quit freezing our elbows.
I take it as a car charm and just deal with it.

 

[raMBow]

Thanks raMBow My plastic stems are in tact. My question is are they supposed to be attached or do they slide in and out of the other part freely? Looks like I will try and take out those plungers all together and if I have heat, I'll buy a duovalve. Where did you get yours and how much if you don't mind me asking?

They are supposed to be attached. The point where mine broke was how far in they were. Held in place by a stamped scored area (not best description) of the upper half. How I was to know that ahead of time??? Nor do I see how one could take it apart in place w/o breaking them. At any rate I do not recall what it cost me. But it was quick and fully restored the heat and A/C to proper functioning. So something was amiss regardless.

 

[Sean Garrity]

Thank you everyone for the help on this. This is a great forum and very helpful in making me want to stay a MB owner. Ha. I found the problem, the duovalve for sure. From all the posts and pics I found the arrow pointing toward the valve and saw that the brass/plastic stem parts should be attached/fixed to the solenoid/plunger there for lifting the plungers up and out of the way for heated water to flow in to the heater core. Sorry for all the /// just don't know what to call them exactly. I have removed the brass/plastic stem parts that where shown to break as in raMBow's pics and voila, heat. My air con even blows cold when acc is turned down. I know it is not right and my seperate climates will not work so I will be ordering a new duovalve, but for right now I have heat. Yay. Thanks again, EVERYONE. Next problem is transmission won't shift unless I do select gears in order when it's cold out. Anybody have that problem? I've heard to check the TCM for fluid and the plug on the side for a leak. I'll start a new thread soon on that one if needed.