Air only comes out of defrost, any easy fix? - PeachParts Mercedes-Benz Forum

300SD81 · #1 02-02-2007, 08:30 PM

Having the air only come out of the defrost vents and none to the main ones is really annoying in the morning. The windshield is so cold in the mornings that the (fairly hot) air is barely warm by the time it reaches the top. Is there any easy way to make it come out the main vents, but still be able to use defrost? I have disconnected the vacuum lines to the system due to a bad leak somewhere inside. Not interested in doing the work neccessary to completely fix it right now. Or really working on the car at all except for neccessary maintence, its just too cold out.

Bio300TDTdriver · #2 02-02-2007, 09:27 PM

but on the 124s the defrost is the default mode when the pods are not working correctly.

Chris

Brian Carlton · #3 02-02-2007, 10:19 PM

Quote:

Originally Posted by 300SD81

Is there any easy way to make it come out the main vents, but still be able to use defrost? I have disconnected the vacuum lines to the system due to a bad leak somewhere inside. Not interested in doing the work neccessary to completely fix it right now.

The system will not let any air out of the dash vents when heat is demanded. All the air should come out of the floor registers with a slight leakage across the windshield out of the defrost when the setting is in the economy position.

When the system does not work, it's a fairly lengthy job to open it up and find out which vacuum pods fail to hold vacuum and replace those pods.

Typically, the large dual vacuum pods are the one's that fail. These are the defroster pod and the two main door pods.

When you're ready, we can talk you through it.

300SD81 · #4 02-02-2007, 10:24 PM

So theres no easy way to tempoarily rig it to blow hot air out something other than the defrost vents? Its been in the 20s lately, and the heat is almost competely useless in the morning since the windshield takes forever to warm up even a little. I have the remote start alarm on a timer to start the engine about 15 minutes before I leave the house, even then, since all the airs blowing on the ice cold windshield, I barely get any warmth until I get to school. I plan on fixing everything on the car eventually, I just don't have the money or enough time to take teh car apart right now.

Brian Carlton · #5 02-02-2007, 10:34 PM

Quote:

Originally Posted by 300SD81

So theres no easy way to tempoarily rig it to blow hot air out something other than the defrost vents? Its been in the 20s lately, and the heat is almost competely useless in the morning since the windshield takes forever to warm up even a little. I have the remote start alarm on a timer to start the engine about 15 minutes before I leave the house, even then, since all the airs blowing on the ice cold windshield, I barely get any warmth until I get to school. I plan on fixing everything on the car eventually, I just don't have the money or enough time to take teh car apart right now.

You've got vacuum leaks in one or several pods. These pods won't open their respective vacuum doors. The defrost pod is the default. When it fails to close, the door is wide open.

You cannot fix it unless you go though the system, locate the bad pods or switchover valves, and replace them. It's not a horrible job. Unfortunately, you must open up the system, find the bad pods, and wait until you get the new pods. It's difficult to drive the vehicle in the interim.......but.....not impossible.

kerry · #6 02-02-2007, 10:34 PM

When you disconnected the vacuum, I believe you put the system into the default mode. This mode puts high heat out of the defrost vents. Until you solve the vacuum problems, you will have only full defrost heat.