paige320

Hello, all. I am new to the forum, as well as to Mercedes-Benz. I am a new owner of a 1998 e320 4matic wagon. Mechanically, it is in excellent condition and has the smoothest ride I've ever driven. We bought it knowing it has AC issues, however.

It has had the blower motor and cabin filters replaced, as well as some wires that had been chewed up by a rodent. The car had sat idle outside the previous owner's home for a long time. These wires that were replaced are connected to temperature sensors. Fluid levels are good, as far as 134a and freon. The error codes that were there before have been cleared and reset.

So I start the car and it blows hard and cold for about 1 or 2 minutes, and it gradually gets warmer. It's not hot air blowing out, just regular air blowing at the same force the cold air was blowing. The Auto buttons on both the left and right side of the climate control panel are always lit up. I don't know if this has anything to do with it, or if I don't have it on the right settings. I really don't want to have to take it back to the shop, but I will unless this is an easy fix.

Thank you!! Hope to hear something soon.

kajtek1

You will find about a million topics how to troubleshot this car AC system.
Best if you have never done it before - go on youtube and follow the procedure to clear AC errors and then to read the sensor values.
For full troubleshooting you need to read the sensors on 3 occasions.
1. in the morning before engine start
2 in the afternoon when entering hot car engine off
3 about 2 minutes from pt2 after engine start, when after reading sensors 1-8 scroll back to 7 and observe pressure change during driving.
-report back with numbers.

paige320

How do you read the sensor values? Is this different from the error codes found from the climate control?

kajtek1

https://www.youtube.com/results?sear...+ac+diagnostic
enjoy

Plutoe

You have been spammed and are being misinformed---simply do the actual value test and fault test---both of those test are on the forum and will pinpoint in minutes what is causing the problem--watch out for advice to take fan blades off the fan.

Once you do the tests post the data and it will be analyzed!!

paige320

Yes, I know how to do that. There are 0 error codes as of now. @Plutoe, is this the same as "doing the actual value test and fault test?"

paige320

Oh, I found this. I guess this is what you mean:

Start your car.

Press the “AUTO” button on your climate control.

Turn on the A/C (i.e. “EC” light must be off; if the light won’t shut off, continue with this test. We’ll address your “EC” light on the next page.)

Let the car idle for about 3 minutes.

Set the temperature on each side to 68°F. You can do this quickly by pressing both the red and blue arrows simultaneously.

Press and hold the “REST” button for five seconds or until the left side of the display says “01.” The left side indicates which sensor you’re checking. In this case, #1 is the in-car temperature sensor. The right side of the display shows the value of sensor #1 (in this case, the actual in-car temperature).

Press the “AUTO” button on the left side to move to the next sensor. Press the “AUTO” button on the right side to move to the previous sensor.

Record the ID number of each sensor (left side of display) and its corresponding value (right side of display). For example, in the picture on the right, you would record that sensor #5 has a value of 6.

You only need to do this for sensors #1-8. You can write down the values for the other sensors, but they’re not really related to air conditioning function.

When you are done, press the “REST” button again to exit the self-check mode.

kajtek1

O errors is good, but you need to read sensors I listed above.
Here is the video from the list that address this procedure directly

Plutoe

No, the three tests(actual value, fault and flap) are all separate, but all use the AC control unit for the data output---very simple to use, just do the test and post the data and forget about all the HS misinformation by spammers!!

paige320

Thanks! I have written down the readings. Is it possible they are in Celsius? Because my numbers are considerably lower than the guy's in the video.

Before starting:
1 - 28
2 - 24
3 - 25
4 - 25
5 - 62
6 - 27
7 - 05
8 - 25

3 Minutes after starting:
1 - 25
2 - 25
3 - 21
4 - 21
5 - 62
6 - 61
7 - 07
8 - 36

After driving around for about 5 minutes:
1 - 28
2 - 25
3 - 25
4 - 25
5 - 64
6 - 86
7 - 06
8 - 29

Oh yeah, and another thing I forgot to mention: Every time I restart the car it starts blowing cold air again, then again, gradually starts to warm up.

kajtek1

It is on 'C. For some reason some of them display in C, some in F.
From the readouts you have
1. bad evaporator sensor.
2. low refrigerant pressure.
So replace the evaporator sensor and add a can of refrigerant and repeat the readout if the problem still exist.

paige320

Ok, I called the shop and told them about this. I'm taking it in Monday morning. Once we get this resolved, I'll write back. Thanks!!!

paige320

I forgot to write back. It was indeed the evaporator temp sensor! Thank you so much! The AC is icecold 😎

Beverly Sharp

So what should the evaporator sensor read? Mine reads 40, 37, and 35. Is this good or bad? I ask because my a/c is cold, but certainly not "ice cold." Refrigerant level is ok.
James

kajtek1

Good working evaporator will come down to 2C or 35F.
There must be program that stops at this point to prevent freezing the coils.
If that is not freezing your elbows, you must have problem with air flow.

Beverly Sharp

Good to know. How do you check "air flow?"
J

Plutoe

We will do this the polak ***** way-------to what degree do you want to check air flow and from what vent and at what setting and at what fan setting??

kajtek1

Do you see the blower coming to high when you start hot car?
Post all sensor readouts, then we can tell more.

Beverly Sharp

Ok, give me a day or two.
James

paige320

I'm back again, after almost 2 years. My A/C stopped working, of course during Summer.

As stated before - It has had the blower motor and cabin filters replaced, as well as some wires that had been chewed up by a rodent. The car had sat idle outside the previous owner's home for a long time. These wires that were replaced are connected to temperature sensors.

I also had the evaporator temperature sensor replaced when that was found to be the issue.

Right now, it sounds like it's on like the fan is trying to blow, but I don't feel any air, hot or cold. Here are the readings I got after driving it -

In Celsius

1 - 46
2 - 33
3 - 36
4 - 37
5 - 21
6 - 96
7 - 11
8 - 47

Any idea with these symptoms and numbers???

kajtek1

with partial test - partial diagnosis.
96C indicates engine overheating.