W210 AC question for MB Techs (UPDATE)
 

I have a 98 e430, and the ac blows colder on the passenger side than on the drivers side. Are there 2 seperate evaporators, or is this a control module problem. Could this be a symptom of the system being low on freon?

Only 1 evaporator on the car. Try turning on the ac and holding down the REST button for 5 secs. Your display will change to a diagnostic one. The numbers run from 1 -41 but many are missing.
1=inside air temp
2=ouside air temp
3=left hearter core temp
4=right heater core temp
5=evaporator temp
7=refrigerant pressure in bars

You got through the numbers by pushing the auto button on the panel. Left side auto increases the # and right side auto decreases the #.

If your temp sensors are bad in either the left or right heater core it could be your problem. To check for this, leave the car sit for a few hours and power the electric system without starting the engine, hit the REST button and go through the sequence to get to #3 and #4. If the sensors are OK they should read the same or very close. If they are far off, you have a bad sensor.
Hope this helps.

What ranges should the following items fall in?

Evaporator temp
Heater core temps
Refrigerant pressure

Thanks~!

low on freon, ck your freon level

the water temps were 81 & 80 degrees when the car had not been run for 4 hours. I started it up, and drove for a while in 93 degree temps. After a while the drivers side was 61 and the passenger was 48....... does that mean the drivers side water temp sensor is bad, or just that the system is low on freon and the evaporator on the drivers side is not getting as cold? in the flow path, is the passenger evaporator 1st?

this is actually pretty interesting except the part where its hot out and not very cool in the car...

when driving at freeway speeds the freon pressure was showing 192.... I'm assuming that is 19.2 bar?

Sterling

The numbers depend on numerous factors. It appears that one of your heater core sensors may have failed. Your refrigerent pressure (#7) should not read 192. It should read in a range from about 8 to 18 depending on the temperature outside. (14.7 psi per bar) You may be reading #8 which is your refrigerent temperature...then 192 would seem correct.

The thing you want to do is not turn the ac on and just power the system up after letting it sit for several hours, preferably overnight. Then the temp readings at 1,2,3,4 and 5 should be fairly close to the actual outside air temp if you are parked in a garage. If one reading deviates from the others by a large margin, you found your problem.

BTW, I'm not a tech but do ac work on my own vehicles when they need it.

Only one evaporator but some trick of airflow causes any reduction of refrigeration capacity to cause one side to be warmer. Simplest answer is low on refrigerant.

refrigerant pressure ranged between 12 & 14 outside temp is 73 (after dark) sounds like it may be low on freon...

I added approximately 6 oz of freon, the pressure reading is no 16 and both sides are blowing the same temp.... those onboard diagnostics are handy.....

Thanks~!

Sterling

my refrigerant reading is 06. I'm sure i need to recharge the freon. how much should a fair price be to recharge it.?? please let me know as I just noticed today it wasn't cooling like it used to. thanks!

I had the same problem with my car about 2 weeks ago. I did add some more Freon. But it feels like the one side is a little warm. Is it possible that the Mono Valve is letting a little wam water through, on the left hand side? I just replaced the evaporator temp sensor.. All the values are close #2,3,4,5 Now.. #5 was way high...

Were did you add the freon, I can not find the valve on my E320.

I added the Freon to the system in the upper right hand side of the engine bay. On the right side of the engine toward the back facing the engine..
I left my camera at home I was going to run ourside and take a picture for you..


Peter

Hey Peter,
I appreciate the help, but I still couldn't locate the valve. Is it something that you need to unscrew to see? It would be a great help if you could take a picture whenever you got the time. I hate driving with the A/C barely working!
ben

One thing you can do is follow the aluminum lines coming from the compressor on the lower right side of the engine..

Peter