secondchance550

I'm a newbie here. Got a 2007 SL550 recently. I have a situation where AC works fine after first start of the day (can be mid day as well as in the morning). After that, even after 8 hours of being parked in the parking garage at work, AC blows as if compressor is not running. Looks like compressor is mounted low on the driver side and tough to tell whether running or not.
I had my mechanic check and he tells me there is sufficient freon. Also, replaced evaporator temp sensor but still not cured...
Anyone had a similar situation? Any suggestion?

Rudeney

The compressor uses an internal swash plate and not an external clutch, so you would not be able to see if its working just by looking at it. Since the system works intermittently, I don't believe it is an issue with refrigerant levels. One thing it could be is the internal humidity/temperature sensor in the overhead control panel. If this goes bad, it will not allow the ACC to activate cooling. I am not sure, but I believe the signal from this sensor is ignored with the top open. If that is the case, and the AC works with the top down, then I'd look to repair this sensor.

secondchance550

I'll try running ac with the top down and see if this makes compressor come on line. This overhead sensor you are referring to - does MB sells the sensor only or is this an integral part of overhead light assembly?
Also, there is another sensor in the middle of HVAC control, right? Do you know how that sensor contributes to the system?

Rudeney

The sensor in the overheard conrol panel detects humidity. The sensor in the ACC panel detects temperature. Unfortunately, the OCP is all one part. However, if you determine that the sensor is bad, there is a much less expensive solution:

http://www.benzworld.org/forums/c209...re-sensor.html

secondchance550

I tried with the top down and didn't seem to make any difference. Instead of throwing parts at it, I am thinking of getting a icarsoft MBII i980 scanner. From what I see, this scanner should be able to help me see what various sensors are doing. Are you familiar with this scanner? Anyone familiar with icarsoft scanner?

secondchance550

One more thing - about a week ago, early morning and AC was working great - I saw whitish residue, sort of looked like ash, hanging off the slots between the left and right side temperature control dial, coming out of what I suspect is cabin temperature sensor. I am so tempted to take HVAC control panel, disassemble and see what's in there. From what I've been reading, most likely, a thermistor and a miniature fan?

next2pool

Even though it has a variable swash plate like most new cars, it still has a clutch as well.

Rudeney

I don't have iCarsoft myself (I use SDS) but I have heard very good things about it, and it should be able to read the actual values of the ACC.

There is no clutch on the compressor that you can see operating. You'll need scan tool to tell if the compressor is engage or not.

Cesar Fernandes

i Everyone,
I have an SL350 (R230) 2007 and the a/c works perfectly, except in very hot days if I park the car outside in the sun light. It doesn't blow any air.
After the car lows the temperature it starts to work perfectly again.
Can anyone help?
BR

Plutoe

You have a faulty AC control module---to confirm you need someone with factory or equal diagnostic software to interrogate the system!!