Heater Valve & Other Climate Components - PeachParts Mercedes-Benz Forum

BrierS · #1 08-03-2004, 10:01 AM

Probably one of the most covered general topics . . .

My '87 300TD now has functioning A/C and has always had heat. However, while I wait for my "MB Climate Control" manual to arrive Priority Mail I am still trying to solve some of the problems.

My Sampler Blower spins and barely hold a tissue with the hose off. Connected, it will not draw smoke into the actual sensor. Additionally, the connected hose runs along the side of the body inner body panel and has no foam/insulation on it. If it is supposed to have it, there would be only 4-6" where it could be installed.

I believe I have located the water valve (just forward of the battery with two heater hoses connected and a 3-wire connector) yet I am not certain since I have been unable to locate a photo. Since I have had heat right along am I correct in thinking this valve is operating correctly?

Under the dash, on the right side of what I call the heater box, there is a unit that has a series of vacuum lines attached. Forward of that is a type of vacuum actuator that has a flat arm attached to the heater box. That arm does not move no matter what I do with the selector buttons and the climate wheel. Since I am not getting air flow through the proper vents when using the selector buttons I am suspicous that may be part or all of the problem.

I have also noticed that there is air flow corresponding with the blower fan coming out of the engine compartment fresh air ducts (just forward of the wiper under the bonnet).

What I am trying to solve is:
1) Getting colder air (system is fully charged)
2) Getting it to come through the proper ducts/vents

Any help would be appreciated.

compress ignite · #2 08-03-2004, 10:17 AM

You are most likely not recieving the full benefits of recirculated
pre-cooled air.The vaccum actuator that you describe as not
working may have other non-functioning brethren inside the
dash.(what kind of temps are you getting at the center vents/
with what kind of ambient air temps?)
I have not had time to delve into the service C.D. for H.V.A.C.
problems.
I haven't any Known Factors for the Sampler Blower Mtr.
The valve you describe (in front of the battery) is either the
H2O valve OR it's the "Auxillary Water Pump" another benefit
of Celtic Engineering Schools. ['90 300D]

BrierS · #3 08-03-2004, 10:30 AM

Temps at the center vents . . . I am unfortunately one that has not yet bought a thermometer to hang from the center vent. That will change as of later today.

I am getting approximately 45-50 degrees F while the ambiant temperature is mid to high 70s. Though I am going out to check it now.

compress ignite · #4 08-03-2004, 08:14 PM

The auxillary H2O pump (it's actually inside the engine
compartment- from the diagrams for your model) is not
in the "Battery Compartment"
The valve you correctly identified (in front of the battery)as
the Mono-valve is situated vertically.
If you will remove the glove compartment you will see the
vaccum block on the left side and with a Plastic "Mighty-vac"
from Autozone (about $25.00 U.S.) you will be able to self
diagnose (with a vaccum diagram)

BrierS · #5 08-03-2004, 08:24 PM

Thank you. I purchased a replacement "Mighty-Vac" and have been using it as I progress through the vacuum systems. Not knowing the schematic of the hoses within the dash (bought but have not received the Climate Control Manual) I wasn't certain what their labels meant. I should be receiving the manual soon. I have the CD set and have not yet found enough readable detail pertaining to that bank of lines.

I'll post as I progress.

#6 08-03-2004, 09:10 PM

I hope I don't sound rude in asking this, I certainly don't want to sound that way. What exactly are the symptoms? You're all over the place in describing what's going on.

I remember in a college Physics class there was this guy who would have scribbles all over his paper and try to ask questions of the professor in a very unorganized manner. He had all the information but it was scattered everywhere.

What exactly is the problem? Is your problem that you have 45 to 50 degree air with 75 degree ambient?

Are you getting condensation drain water out the bottom when the a/c is running? If so, then the refrigeration portion is probably okay, and I THINK that's why you're describing all these other things.

If your refrigeration is okay and the heater valve is not allowing LOTS of hot water, then you are probably getting fresh air instead of recirculated air. Go to that series of vacuum lines just behind the glove box and remove the top two one at a time and apply no more than 4 inches of vacuum and see if it will hold vacuum. If one or both will not hold vacuum, the problem is your fresh air/recirc pods in front of the HVAC box at the top center of the dash.

I have my 300E apart as we speak replacing them. This is a HUGE project. The entire instrument panel must come off to replace them.

But, DON'T jump to any conclusions until you've done some analysis. If the sampler blower is turning when the ignition is on, I would forget about it for the moment until you check the pods. If the heater valve or the control of the heater valve were bad I think you would be absolutely frying, so my gut says that's not your problem.

Check the pods and get back to us.

Best of luck,

BrierS · #7 08-03-2004, 09:28 PM

Larry Bible,
You just gave me another place to turn. After having read what you wrote to other forum members, I knew I was looking at a heater valve not a mono valve. When you described the sampler function I was able to find and check if it was operational.

I'll test the upper two lines one at a time with no more than 4" of vacuum and post again.

I have followed your progress on your project and don't envy you yet.

Condensation runs out so I knew I was probably okay there.

And I don't take constructive critisim as being rude.

Thanks

BrierS · #8 08-04-2004, 09:47 AM

Okay. Top two lines do not hold vacuum. Oh well. I have followed your plight on this forum.