Cold Center Vents, Hot side 93 190E

[meltedpanda]

Trying once agin to help out a friend.
AC works but only cold at center vents and hot blows at the same time out of the side (far righ/left) vents

Place to start to look? ACC unit?
Tried search but really did not know what to search for?

[softconsult]

Sounds like vacuum pod failure. The pods control the various air flow flaps. On 300E you can check for vacuum leak with a MityVac at the connection junction box behind the glove box. No idea on the 190.

Steve

[meltedpanda]

I suspect that also but it does not make sense to have hot air, I could see no air or uncooled air but hot air

[mctwin2kman]

Vacuum leak on the W201 will result in full heat out the defroster vents. Pod failure and you could lose enough vacuum when that pod is selected to go to full heat as well. The W201 no heat comes out the center vents, only outside air and AC air. So you would not get heat out the center vents anyhow to match the heat of the outer. But you will get cold since the air never flows over the heater core to get to the center vents. But the AC will still come out them vents. So start looking for a vacuum leak. Since by design when the temp wheel is in the cold position and the AC selected the Aux pump will turn off and the heater valve will close. Maybe your heater valve is where the Vacuum leak is or maybe the vacuum leak is at the vent pod. When you select other vent controls on the CC unit do you get proper air flow at the correct places, in other words are the right flaps opened and closed to match your selection?

[meltedpanda]

I will check other positions and let you know, this is not my car so I am not sure. On my 126 I can get at most of the pods, what about this baby, are there places I can check without removing the dash?

[mctwin2kman]

Originally Posted by meltedpanda

I will check other positions and let you know, this is not my car so I am not sure. On my 126 I can get at most of the pods, what about this baby, are there places I can check without removing the dash?

If you remove the glove box you can see the one for the blend/air doors. With the Gauge cluster removed you can see the one for the defrost and I believe one more. With the radio removed and the panel or cassete holder removed you get the legs one, vents one and the recirc door one. The vacuum distribution unit is under the passenger side vent and can be seen with the vent removed but better with the glove box removed. Check the vacuum check valve near the fuse box under the hood. should be one line coming from the engine through the firewall then to a Y splitter, one for the economy gauge that goes straight into the car, and one for the CC system that goes to a two way check valve and one line into the car and one line over to the passenger side and to the resevoir in the fender. There is also one more pod in the system, it is under the debri screen under the wiper on the passenger side of the wiper. That is for the Heater Valve, it closes to stop flow into the heater core.

[meltedpanda]

I torn into this problem this weekend and found a part
#0008309608 just behind the passenger vent that was screaming like a cat whose tail was stuck in a fan.
I removed it and it appears to be some type of small fan that intakes air and blows it into a tube that then dives into the bowels of the car. My hopes is that this is related to the vents blowing hot air while the center vents blow cold AC.
My luck would be that it is just another part going south....
Ideas welcome.
I tried to lube the part with little luck turns very slowly and loudly when 12V applied on the bench setup

[meltedpanda]

replaced the defective part, but did not help the vent problem
center vents still cold , and the side and defrost vents blow warm/hot air. I believe it is the vacuum issue or center pod failure. Question now is this a DIY or dealer /experienced mechanic. I have average skills, but tearing into the dash scares me a bit
anyway I can bypass these pods or is failure to close a result of insufficient vacuum and therefore must be fixed/
It is hot as @#$% here and this makes driving this car nearly impossible.

[mctwin2kman]

That fan is for the Interior Temp Sensor for the Climatronic Climate Control. It sucks air through the tube that leads to the temp sensor by your rear view mirror. Tells the Climate Control the cars interior temp to hold the temp you set on the temp wheel. You have a vacuum leak somewhere. Check the vacuum connection at the firewall next to the fuse box. There is a check valve there that splits the vacuum to two line, one to the interior to the right side vent to the distribution device and one to the vacuum resevoir under the passenger side fender. There is another line that comes from this area and goes to the economy gauge. The vacuum distribution system is controlled electronically by the climate control unit and distributes vacuum depending on your CC settings to control all the vacuum pods in the HVAC system. There are three behind the radio ash tray panel. One on top of the heater box under the dash, and the remaining one behind the instrument cluster. The vacuum lines have connections under the glove box as well due to vacuum line not being long enough to make it all the way. There is also a vacuum line going to the Heater Valve which is under the debri screen located under the wiper. It is on the passenger side next to the air box that contains the squirel cage fans for the HVAC system. You could also have a bad vacuum distribution device or CC Unit. But start with the easy ones of looking for a serious vacuum leak due to a disconnected line or bad Pod.

[meltedpanda]

great info, I will check out the lines I can get to, if its the pods I am going to send her to an expert

[bcm]

what is an obvious indecation of a bad pod. what is suppose to do, verses what its not?

[brewtoo]

Originally Posted by bcm

what is an obvious indecation of a bad pod. what is suppose to do, verses what its not?

Use a Mityvac hooked to the lines, one at a time, behind the glove box. If the pod will not hold vacuum it is a bad pod.

[Stan Pittman]

Every time I've seen this problem it turned out to be the double vacuum motor behind the instrument cluster was leaking vacuum.