Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   PeachParts Mercedes-Benz Forum > Mercedes-Benz Tech Information and Support > Tech Help

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 12-15-2016, 02:18 PM
lsmalley's Avatar
Registered User
 
Join Date: Oct 2006
Location: California
Posts: 1,992
W201 heater valve question

Just replaced my heater valve and I noticed that when I have it set to cold it works fine, but when I come to a stop and accelerate again it blows hot air for about 10-15 seconds then cools again. I originally thought vacuum leak, but it only does it when accelerating from a stop. Any suggestions or things to check?

__________________

1990 190E 2.6L
Reply With Quote
  #2  
Old 12-16-2016, 12:31 AM
w123fanman's Avatar
Registered User
 
Join Date: Jun 2011
Location: Georgia Tech, Atlanta, GA
Posts: 1,600
Quote:
Originally Posted by lsmalley View Post
Just replaced my heater valve and I noticed that when I have it set to cold it works fine, but when I come to a stop and accelerate again it blows hot air for about 10-15 seconds then cools again. I originally thought vacuum leak, but it only does it when accelerating from a stop. Any suggestions or things to check?
Answer this question for me, does the defrost flap come open as well? I had a similar issue where the defrost flap was coming open part way sometimes even when I had it set to just the vents or feet, it ended up being a shot defrost pod. The way you can test the vacuum components in the HVAC system is to access the vacuum switchover unit that is behind the glovebox then use a vacuum tester to pull a vacuum and see if it holds.
__________________
Current: 80 300SD OM606 project, 83 300D 5-speed project, 88 Yugo GVX, 90 300D OM603 swap, 90 Lexus LS400, 91 F150 4.6 4v swap, 93 190E Sportline LE 3.0L swap, 93 190E Sportline LE Megasquirt, 03 Sprinter
Reply With Quote
  #3  
Old 12-20-2016, 03:34 AM
Registered User
 
Join Date: Jun 2000
Location: Saugus, CA USA
Posts: 2,035
You have a vacuum leak

When you accelerate the engine vacuum drops and the default is heater and defroster on, I guess its a safety feature. For the heat to come on both the water valve and the blend air actuator need to be enabeled, that is no vacuum.
Reply With Quote
  #4  
Old 12-20-2016, 10:43 AM
lsmalley's Avatar
Registered User
 
Join Date: Oct 2006
Location: California
Posts: 1,992
Yes, I tested and tested everything and all the vacuum components are working. After looking at this diagram, I do see number 48 (orifice vented for 20 seconds) must be what causes it. As I said, upon acceleration, heat is present for about 10-15 seconds (it must be 20 seconds per the diagram). What I did was added a second Y-splitter and a one way check valve. This diagram is accurate, but my car has an economy gauge, the "drt" line, the "rt/gn" line, and the "mgn/rt" line getting a direct feed via intake/2-way check valve. I added the check valve to the "mgn/rt" line and it seems to have eliminated the 20 second vent and seems to not have changed anything else. I'll see how this holds up or if I notice anything else that changes.
Attached Thumbnails
W201 heater valve question-2011-01-14_021117_42244995.jpg  
__________________

1990 190E 2.6L
Reply With Quote
  #5  
Old 12-21-2016, 07:09 PM
Registered User
 
Join Date: Dec 2003
Location: Rogersville, Missouri
Posts: 187
Be sure the rt/gr line to #33 reservoir is not leaking. I have seen this line decompose when in contact with seam sealer as the line runs across the firewall
__________________
Paulwho
1987 190E-16v,
Reply With Quote
  #6  
Old 12-21-2016, 09:17 PM
Registered User
 
Join Date: Dec 2006
Posts: 3,875
I gather this is a gasser, it's important to know that. At idle, manifold vacuum is very high. When you stomp on the pedal, it approaches zero. The heating system reacts to zero vacuum by supplying max heat. You have two components which keep this from being a problem: check valve 31 and vacuum reservoir 33. I would guess that either the check valve is bad or one of the rubber connectors is leaky as has been mentioned. To help you along, here's a photo of the vacuum reservoir, it's inside the left fender:

http://www.coolcatcorp.com/190Restoration/Mercedes23.jpg
Reply With Quote
  #7  
Old 12-22-2016, 07:50 AM
Registered User
 
Join Date: Jun 2002
Location: Conway, SC
Posts: 306
I agree with Paulwho. That plastic line to the reservoir deteriorating is a very common problem.
__________________
Mercedes Benz Master Tech - Retired
Reply With Quote
  #8  
Old 01-19-2017, 04:44 PM
Administrator
 
Join Date: Mar 2016
Location: Los Angeles, CA
Posts: 1,901
If anyone is still looking for info on their heater, or parts of it; check out the below tech article.

Mercedes-Benz 190E Heater Core Replacement | W201 1987-1993 | Pelican Parts DIY Maintenance Article

Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On




All times are GMT -4. The time now is 05:02 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page