1. Is there an inexpensive way to bypass the monovalve for the winter? I am only getting lukewarm air out of the heater and it is getting colder out. I don't want to buy a new monovalve or even a monovalve repair kit as I need the money for other repairs.

2. Is there a manual fix to get the heat to blow out the floor ducts? I spent a lot of time yesterday trying to fix the acc and the air still comes out of the defroster and console vents. Since it is winter, I would always like to get some of the heat out of the floor ducts.

Thanks again.

BTW, I was able to open the trunk on my 1983 300d by following directions on an old post on this board and employing my mityvac. The prior owner had rekeyed the ignition but not the other locks so I had no other way of getting in there. There was lots of interesting stuff inside, kind of like a time capsule.

The monovalve has a line going in and a line going out. When 12v applied, the valve will close, That is how heat is regulated with the ACC. To go without just remove the assembly and run a piece of pipe between both lines, then the heat will always run hi. You will need to keep punching the buttons on and off to avoid getting fried inside.
BTW, I had a thread about the monovalve a couple of weeks ago, it was not working. Someone here suggested I check the electrical connection. I Pulled the two lead connector off the top, and noticed the posts were oxidzed. Cleaned them up and now heat works great. Don't know what yours is doing, but thought I would throw that in.

maybe I'm mistaken about this, but a properly working monovalve will pass fluid with no current, i.e., you can pull the plug off it to get full flow. But depending on the failure mode, it might not open if something is wrong. But for a cheap and easy check, unplugging it is a good place to start.

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

I will give that a try. Sounds like a great idea.

The exception to that is if it freezes closed. Known to happen.

lukewarm air (at idle or low rpm) could be aux. water pump too. I'm trying to get mine to work right now- have determined that I'm not getting power to the pump via the wires...

if that works, unplugging the monovalve should deliver hot only air.

if your thermostat is working properly...

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It was pretty cold inside the car this morning, so I don't think the monovalve experiment worked. Could be the inner workings of the monovalve or just the fact that it was about zero degrees outside. The engine never got past 60 degrees centigrade, so I will next try blocking off part of the radiator. I don't think it is the thermostat because the car stayed right at 80 degrees until the cold snap hit. I am also going to spend a bit more time trying to get the flap to the floor vent to stay open.

You might try some warm soap and water on the vacuum lines where they plug into the rubber tees. That can get leaky there, sort of sounds as if you have minimum of vacuum getting to the vents.

After the engine has heated-up to normal temperature, check the hoses at the mono-valve.

If one of the mono-valve hoses is hot, while the other hose is cold, than your mono-valve is stuck closed. If both hoses to the mono-valve are hot, than your problem is elsewhere.

Phil

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'95 E300 Diesel, 264,000 Miles. [Sold it]