1999 S500

I have a 1999 W140 S500 and when I accelerate, the center vent valves cycle closed and then open after a bit while operating the AC. The AC blows ice cold even in florida summer. Right now, it works otherwise but it is annoying. I can also feel the motor idling a little rough every now and again. I think that there it is a small vaccuum leak but I am not sure.


Anyone ever had this problem? Is this one of those $1000 labor for the $25 part things?


Thanks,

Mark

Plutoe

Look down 9 threads and you will find the two AC self tests-----do the tests and post the data-----Other than that there is the "finger in the wind" test!!

1999 S500

I tried doing the test but the '99 has a different set up. No left or right wheel to turn to the red or blue.

Plutoe

Is your AC unit digital, meaning do you have an auto button on either side of the AC control unit and a digital readout for the two zones?

Additionally what is your VIN??

1999 S500

1999 S500 Grand Edition VIN: WDBGA51GXXA419433


It is digital with the Auto Buttons on each side.

Plutoe

That is good because after 1995 its digital and the two test for your year car is the same as the W210---those tests are within the stickies or you may have to search---the big difference is that for your S read out data for number 1-8, 9 is not assigned, 10,11, 20thru24 and 30thru35.

The fault test is the same except you may get xxxx(4 digit) or xxx(three digit) readouts on the screen----The S class has much more detail so be patient

1999 S500

OK,

Thanks for the info. I will take a look.

1999 S500

I got the car back today.

The motor does not provide vacuum. The AC Vents are worked with vaccum supplied by the PSE Pump under the back seat. The pump is providing the vacuum, but there was a leak in one of the lines going to the passenger front seat. I had them cap off the line and all is well again.


It is the rough equivalent of flipping the garbage disposal switch and the garage door opening. Go figure.