More monovalve questions - PeachParts Mercedes-Benz Forum

merrim19 · #1 09-11-2006, 10:17 AM

For model: 1986 300E

Everything I have researched on the monovalve tells me that if my heat is always on or coming in and out, I should replace my monovalve.

However, this is not the case. I have zero heat. Coolant levels are fine. Fuses in main box under the hood are all fine. The blowers are all still strong. I have inspeced my monovalve and the gaskets all look good. If it is a monovalve problem, maybe the electromagnetic coil isn't working anymore. I do have a different unit than most models, see the picture below.

Are there any other suggestions why my heat won't turn on? If it is a heat sensor problem, or misc., can you please give me an idea how to tackle that problem.

Thanks a ton. It's getting cold and I need to get that heat working again.

TX76513 · #2 09-11-2006, 12:25 PM

Unplug it and see if you get heat.

merrim19 · #3 09-11-2006, 02:48 PM

I did unplug the heater valve when I took the top casing off. The diaphram looks fine, and there weren't signs of wear. I'm not thinking that this problem has to do with my heater valve. My symptoms dont match other stories.

I'm more inclined to think this is a climate control problem, but spinning the wheel still adjusts the air speed. But its always cold air. Subsequently, my a/c never worked, so I'm only getting an unchanging chilly air flow out of the air ducts.

Would you know if the climate control unit can be disfunctional with heat sellections and also still work with the air flow? thanks

TX76513 · #4 09-11-2006, 03:21 PM

Quote:

Originally Posted by merrim19

I did unplug the heater valve when I took the top casing off. The diaphram looks fine, and there weren't signs of wear. I'm not thinking that this problem has to do with my heater valve. My symptoms dont match other stories.

I'm more inclined to think this is a climate control problem, but spinning the wheel still adjusts the air speed. But its always cold air. Subsequently, my a/c never worked, so I'm only getting an unchanging chilly air flow out of the air ducts.

Would you know if the climate control unit can be dysfunctional with heat selections and also still work with the air flow? thanks

Yes the climate control can be dysfunctional and fans still work.
When I mentioned disconnecting the mono - disconnect and drive and see if you have heat.
There are some threads on soldering the CCU - however if (when) you eventually replace you probably will not get your core charge back.
I am sure when it becomes heat time here - I will have to hit the monovalve with a rubber hammer to unstick it for the cooler time of year. The inside cylinder is very close tolerance and it tends to stick after being off (closed) all year.

merrim19 · #5 09-12-2006, 02:57 PM

I tried driving around since yesterday without the heater valve pluged in, and nothing changed with the heat. it is still consistantly an outside temp coming in thru the vents. what might that mean?

Merkey · #6 09-13-2006, 02:21 AM

Just for your info...
We had hot air blowing in 100deg here in SoCal.
I removed the CC unit and still had hot air and the blower on low pushing it into the cabin!
Seems like it defaults to that?

merrim19 · #7 09-13-2006, 10:39 AM

So I took apart the heater valve and removed the needle that closes the coolant flow. So now I have hot air, I just have to live with having only hot air. But it's getting colder out, so I might not tell the difference.