W140 Ac Help Me!!!!!

[Timlewak]

I have a 1995 Mercedes S500. When I bought the car last summer I had the AC charged. This summer I had to have it recharged (maybe a leak). Anyways It worked fine for 2 months and it wont take anymore ref. and it is blowing hot!!! Its so hott driving my favorite car... someone please help me. I have no clue where to start... Timmy

[John T]

Hi you WILL find this website useful I had simalar problems with my1995
S420. Jim describes evaporator leaks and the remedy

http://pages.prodigy.net/jforgione/MB_S500.html

[emerydc8]

I had a problem with my 400E recently. I thought the system was low, because it wasn't as cool as I liked. So, without gauges, I threw in a "few" cans of R-134A. Then, thanks to Arthur Dalton, I learned that my low speed fans were not working. Once I got the fans working, the air still didn't work well. Finally, I bought some cheap gauges from Harbor Freight ($46.00) and checked the pressures. I found out that my high pressure side was going up so high that the compressor was actually cutting out. Once I extracted some R-134A and got the pressures back down to where the manual said they should be, it worked fine. Do you have the gauges? I know the Harbor Freight tools are generally cheap, but they worked for me and I don't use them everyday anyway. The best thing I did was buy the gauges. I did all three of my vehicles. You'll get a better picture of what's happening and those on this forum with more knowledge than you or me will be better able to help you.

When they recharged it two months ago, they might have actually overcharged it and the higher seasonal temps are now causing the compressor to cut out. Best of luck.

[Timlewak]

I bought a can of ref. at Advanced Auto Parts because it had a pressure gauge and when I went to shoot it in, it built up pressure and then it all at once dropped. I have tried using the control unit to get the DTC's and I followed the steps shown on the website, but it wont display those readings. Someone please help me... I hope something isn't broke or anything... and I really haven't a clue where to start looking and right now I can't spare the extra money to make a trip to the dealer.


Thanks, Timmy

[emerydc8]

That might be normal. I noticed the pressure on the suction (low) side rose but eventually dropped after I introduced freon into my system. Troubleshooting the a/c system without knowing what the pressures are on the low and high side is going to be very difficult. It may just be that you are underserviced or overserviced--nothing more.

When I had my a/c troubles a few weeks ago, I didn't want to hear Arthur Dalton tell me that "gaugues are required for a proper diagnosis;" but, he was right: Without knowing the pressures, it's going to be hard for you to get help from the guys that know what they're doing.

Buy the gauges. It will be money well-spent. You're only looking at 50 bucks. If you blow a compressor out on that car because the system was overserviced, I guarantee it's going to cost you more than that.

[JimF]

Originally Posted by Timlewak

I have tried using the control unit to get the DTC's and I followed the steps shown on the website, but it wont display those readings. Someone please help me... I hope something isn't broke or anything... and I really haven't a clue where to start looking and right now I can't spare the extra money to make a trip to the dealer.
Thanks, Timmy

Your car requires a little different procedure to read the operating parameters.

To read the operating values, do the following;
1. IGNITION : Position 1
2. Press the AUTO button
3. Set both temperature selectors to 72 degrees F.
4. Press the REST button for more than 5 seconds.
5. The left display will alternately show the number "1" and the in-car temperature.
6. Press the AUTO button and the next component number and its value will be displayed.
7. Press the REST button to end the test program.

Start there first. The important readings are #5 and #7 at least to see if it's operating.
#5: Evaporator Temperature Sensor (B10/6) shows the air temp at the vents; should be 40F or lower depending on the outside temperature.
#7: Refrigerant Pressure in Bar. For a properly loaded A/C system you should see around 7 - 9 bar; on a HOT day, in traffic, it can go to 15 bar. Moving should bring it down. (1 bar = 14.7 psi)