A/C problem - EC light stays on
 

I have a 1999 E320 with 98K mile and the other day while driving I reduced the fan speed so I could talk on the phone w/o much fan noise ( i do this a lot) and when i went back to hit "auto" to return the climate control back to normal I noticed the EC light on and it has stayed on.
I've never had an issue with the climate control and it was blowing the same cold air that it always has prior to this episode.
After reading about a tech bulletin from another poster (re: changing regrig. temp sensor before doing anything else), I was wondering if that problem was mainly related to new vehicles and wouldn't pertain to a 7 year old vehicle.
Any thoughts on on what my first steps should be that can help solve the problem in a cost effective manner? Check refrigerant? Get a diagnostic test? just go ahead and change the sensor?

What type of refrigerant does this model use?

Thanks.

This is the second time that I've seen someone post that the EC light is on, but yet still has cold air at the vents.

Ensure (visually) that your compressor is turning, although I believe that it would have to be.

If anything causes the compressor to shut down (either low refridgerant or a bad evaporator temperature sensor), you won't have cold air. So these are unlikely to be the problem.

Does the light remain illuminated when you stop and restart the car, with the van in AUTO mode? I wonder if this could be a bad pushbutton unit.

FYI, your car uses refridgerant HFC134a. The stuff that you can get anywhere. But don't go adding any unless it's really low; you don't want to overfill it.

Ec Light Stays On
 

misunderstanding there. i meant to say it was blowing cold air up until the point the EC light came on, which leads me to believe that maybe the refrigerant level is not too low. is this false thinking?

after the EC light has come on the air flow has definitely been of the economy flavor (lukewarm).

Yes the stuck EC light means the compressor is not running. Usually the case is low freon. But I know about the bulletin you mentioned about the refrig temp sensor. There was a bulletin out on these sensors, you can try to find out about it, but it involved basically "shuting off" the refrigerant temp sensor. It was a bit of over-engineering from the start, they decided the system was well-protected by the pressure sensor, so we were to program the control panel to ignore that sensor all together. NOT SURE on exactly which models this covered though, but was 210 related. I'd get codes read and go from there, or have the freon checked.
Gilly

Search here for N22 and REST to find the procedure to extract the current sensor values and the trouble codes. The current sensor values will help tell if the problem is low refridgerant or a bad evaporator temperature sensor, so post at least those here (values 1-8).

The problem I mean isn't the evap temp sensor, they actually have a refrigerant TEMP sensor, helps calculate the refrigerant level. Didn't work too good so again they decided to have the control unit more or less abandon trying to calculate the level, just monitor the pressure like every other good German car.
Gilly

I believe that I've read a TSB about the evaporator temperature sensor, saying to replace it in every case of non-running air-conditioning. Of course, this one is easy to identify with the current sensor value readout.

The same TSB said to code the unit to not check the refridgerant level (setting the 16 bit in one of the version fields; I don't recall which one).

Dat's da one...
Gilly

If you want to check the evap temp sensor, try this. With the engine running and the ACC temperature set to LO (fan speed two or three), press and hold the REST button until the display changes. Then repeatedly press the left side AUTO button until the left side of the display reads 05. The right side will then display the evaporator temperature (as reported by the sensor). If it's too low the compressor won't engage, same thing if it's implausible. One word of caution though. Sometimes the reading will be in Celsius, sometimes Farenheit.

It's advisable to see if the readings on 1,2,3 and 4 are in Celcius or Farenheit. If the car isn't running, these will all show close to ambient temperature. #5 will be in the same scale, and may show a very crazy reading if the sensor is bad.

Where is the freon temp sensor located on a 2000 S430? Also, where can I find instructions for getting the data for the a/c sensors/pressures, etc for the same car?