Have used search to no avail.

Really appreciate any help you can give.

I have a 1996 S320. Have no been using it for a while. Got some work done on it a while back and not sure if it is since then that the problem has arisen or not.

The problem is this…

When I direct the heat into the footwell area on either the passenger or driver side using the electronic panel above the radio (you know the panel with all the heater controls and the rear window defogger) if does not work.

Loads of hot and cold air but when I adjust the fan speed and the direction up ^ out > or down \/ all I get is a greater volume of the desired air temperature at the windscreen.



Any ideas most welcome.

Thanks in advance.



John

PS used to post under another name here but lost password and have no access to old mail account.

Any thoughts guys?

Froze this morning coming into work.

Thanks!

Looked at teh issue over teh weekend but still no better off.

Thoughts?

John,
The climate control in the '96 W140 is made up of several component "groups".

1. Climate Control Push Button P/B unit (in dash)
2. Vacuum valve block controller (behind the glove compartment)
3. Vacuum tank and vacuum source
4. Sensors (temperature/sun load/pressure,etc)
5. Electrical cabling/harnesses between sensors and P/B unit

In short, its a complicated system that will kill you in dollars if you just "hunt and peck" for the problem. The procedure to troubleshoot this system occupies several "pages" in the Mercedes manuals.

The good news is that the P/B unit (the brains of the system) is able to diagnose a number of basic problems and will store a DTC when it finds an error/problem. Also, the unit will allow you to command individual flap controllers throughout the system.

If you're not familiar with this system, I strongly recommend you get someone to perform the diagnosis for you via P/B unit testing or DTC downloading via the Mercedes Hand Held Tester (HHT) or other good scanner.

On my car, the problem I was having with flap control was in the vacuum valve block controller but it only happened in cold weather. The troubleshooting I had to go thru got me pretty familiar with the system and took a few weeks of my spare time. Your problem could be in any of the above components or the vacuum/electrical lines between them.
If I had to do it again, I'd pay Mercedes to tell you what is wrong and then make the decision whether they fix it or you do. Paying them an hour's labor will save you time in the long run.

Hope this helps.

__________________
KenP

1996 S500 W140 Coupe

Hi KenP,

Thank you for your good advice which I have taken.

The car is now with my Mechanic.

Just hope it wont turn into a massive bill.

Again, thanks a mil.

John

Just for the benefit of others....

My mechanic has located the problem.

Seems like the pump under the seat needs to send a signal (vacuum) to the control box behind the glovebox area.

Well it wasnt. To get the system operational again (for now) he has sourced the required vacuum signal from another source.

System is working for now and when I can afford to be without the car for a priod he will fix the problem now that he knows the cause.

Best for now and thanks all.