a/c vacuum problem? Hot air form sides and def.

timpinson · 08-26-2008, 12:41 PM

Hello,

My 1990 190e 2.6 blows hot air from the side vents and defrost. A/c is working and cools through the center vents. It seems like the sides and defrost start to cool after driving at speed on the highway for a while.... any suggestions? I have listened under the dash for vacuum leaks but cannot hear anything unusual.

thanks in advance,

tim

karora · 09-03-2008, 07:17 PM

Dear Tim, I have the same problem, the hot air is coming from the side vents, I have to drive it for a while till I get cold air, cool air is coming from the center vent which is fine. I watch the forum and see what to do!!?

MTI · 09-05-2008, 04:00 PM

When you can't control the airflow, the likely suspects are either the vacuum actuated valves that open or shut the "doors" to the ducts . . . or the doors themselves. That's for the US "Tempmatic" system. The rest of the world got pushrods and rotary dials.

The bad news is that you have to pull the dash to check, inspect or replace them.

190E-Boy · 09-07-2008, 01:55 PM

The vacuum lines just in front of the drivers side under the hood. There's a small cluster of lines and connectors there, I had a similar issue and replaced the cracked connector with a 10 cent piece of tubing (free from work).

Take them off and inspect them, looks can be deceptive.

Gullwing · 09-14-2008, 08:15 PM

And when you can't find any vacuum leaks and have replaced the valve block?...

I am not getting any vacuum to the shutoff valve to the heater core

sun111 · 12-03-2008, 11:22 PM

I think its designed that way so you can control zones.

08-26-2008, 12:41 PM	#1
timpinson Newbie Join Date: Aug 2008 Posts: 1	a/c vacuum problem? Hot air form sides and def. Hello, My 1990 190e 2.6 blows hot air from the side vents and defrost. A/c is working and cools through the center vents. It seems like the sides and defrost start to cool after driving at speed on the highway for a while.... any suggestions? I have listened under the dash for vacuum leaks but cannot hear anything unusual. thanks in advance, tim

09-03-2008, 07:17 PM	#2
karora Newbie Join Date: Oct 2006 Posts: 7	a/c vacume problem? Hot Air from both sides Dear Tim, I have the same problem, the hot air is coming from the side vents, I have to drive it for a while till I get cold air, cool air is coming from the center vent which is fine. I watch the forum and see what to do!!?

09-07-2008, 01:55 PM	#4
190E-Boy Almost a Member! Join Date: Nov 2003 Location: PA/NJ Posts: 60	look at ....... The vacuum lines just in front of the drivers side under the hood. There's a small cluster of lines and connectors there, I had a similar issue and replaced the cracked connector with a 10 cent piece of tubing (free from work). Take them off and inspect them, looks can be deceptive. __________________ 1996 E300 Diesel Black/Grey 1991 190E 2.6 Brilliant Silver/Black

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09-05-2008, 04:00 PM	#3
MTI MBWorld Fanatic! Join Date: Dec 2002 Location: Honolulu, Hawaii Posts: 2,596	When you can't control the airflow, the likely suspects are either the vacuum actuated valves that open or shut the "doors" to the ducts . . . or the doors themselves. That's for the US "Tempmatic" system. The rest of the world got pushrods and rotary dials. The bad news is that you have to pull the dash to check, inspect or replace them.

09-14-2008, 08:15 PM	#5
Gullwing Member Join Date: Feb 2005 Location: Las Vegas Posts: 121	And when you can't find any vacuum leaks and have replaced the valve block?... I am not getting any vacuum to the shutoff valve to the heater core

12-03-2008, 11:22 PM	#6
sun111 Almost a Member! Join Date: Apr 2008 Posts: 34	I think its designed that way so you can control zones.