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Old 09-11-2006, 11:58 PM
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Join Date: Sep 2006
Posts: 10
Unhappy Inconsistent Heat from Climate Control W220 190E 1990 2.6

Sometimes, the heater works fine, sometimes it warms too little and sometimes it does not function at all.

For 1 weeks I had it set to max heat and it produced none at all. The temperature outside varied from 66F to 80F and inside was the same with the sunroof and windows open. Now, suddenly it began to work once again as I expected it would sooner or later. When it will fail again, I don’t know. In the winter at times it produced heat, but only barely and other times it worked as it should.

So I just bought a rebuilt Climate Control unit. Before I install it, are there any other items that should be replaced or looked at while the dash is out?

For instance, from this site, I learned there may be a Blower Aspirator for temperature sensor ventilation which may be near the Heater Fan Motor (it squeaks off and on during the winter… annoying… any suggestions?). And I learned there may be a Sampler Blower Motor For Temperature Sensor Ventilation on roof rail which draws air from a specific location in vehicle to sample the temperature and relays information to control unit which takes action to correct to desired temperature setting.

Thermo-Vacuum Valve is a two position valve = open/closed, installed in the engine water jacket, when it reaches temperature the valve opens passing vacuum.

Heater Valves… is any brand a good?

So where do I start, what is worth replacing wile in the dash and do I really have all these items as stated?

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Old 09-12-2006, 08:10 AM
Join Date: Mar 1999
Location: Tucker, Ga USA
Posts: 12,153
To start with welcome..

That chassis is a W201..that a/c system uses a heater valve that is either OPEN or closed & then mixes air thru a blend air door. Vacuum controls the blend air door & the heater valve. IF vacuum if removed from heater valve the inside OUTER & foot well vents should get HOT. IF not then the heater valve OR heater core would be the problem..

The sampler motor(aspirator) for the in-car temp sensor on a 1986 car is behind the dash vent on the passenger side. ON a 1987 & later car it is in the dome lamp assembly.
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Old 09-16-2006, 08:45 PM
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Join Date: Sep 2006
Posts: 10

Well, the heat has been out again for three days. Tuesday, I plan to install the new climate control unit (rebuilt).

I swear I can feel just the smallest amount of heat, but so little it would be as if the blend door was closed.

What if the Vacuum control that operates the blend air door is bad? What part is that and how much time would be needed to replace? Is it accessible with the climate Control unit out?

Thanks in advance.

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Old 09-22-2006, 09:34 PM
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Join Date: Sep 2006
Posts: 10
Angry crazy results with new climate control unit w220

Well, the new climate control unit (rebuilt) was installed and now the a/c stopped working and the unit cliks everyminute and turn off the fan for a few seconds and than tuyrns it back on.

I swear I can feel just the smallest amount of heat, but it comes in the center vents and is very very slight.

Warm water seems to go past the auxilary pump, but I wonder if it is bad as well as the "rebuilt controller".


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Old 10-23-2006, 08:15 PM
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Join Date: Sep 2006
Posts: 10
Turn out remanufactured item was tag with wrong model!

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Old 02-28-2007, 10:44 PM
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Join Date: Apr 2004
Location: Berkeley County, S.C.
Posts: 39
M.B.Doc, my 1990 190e 2.6 heater puts out heat just as you said all the time. Where is the heater valve located so I can trace the vacumn lines out? I have replaced the climate control with several units to see if that is the problem, it didn't fix it. I wasn't aware of vacumn on the heater valve as a solution.
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Old 02-28-2007, 11:17 PM
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Join Date: Sep 2006
Posts: 10

The M.B. 1990 190e 2.6 heater is on the right front near the side not far from the firewall. BUY M.B. as the car puts out so much heat it melted the plastic tube that inserts into the feed and the pressure of the clamp caused it to collapse and ultimately leak within a few weeks!

I still have my old climate control that works most of the time, but sometimes gets goofy if you need something to test with.

Check for vacumn, without it the heater valve will stay open and bake you in the car. Then check to make sure that the valve mechanically operates to close. You can alos tell by putting you hand on both sides of the hot water feed hoses. One side will be HOT, the other cold or at least only warm if closed.

Good Luck,
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