Hi. I am having a few issues going on with my C300. It has 52k miles and is in great shape however just recently a few issues came up. The shop asks for ridiculously high repair costs so I want to troubleshoot it myself, plus I like to learn new things.

1. My AC stopped working suddenly. It was blowing very cold air, but one day it just started blowing warm air.
- I checked the compressor and it is being engaged.
- The fan behind radiator works.
- The heater works, hot air is blowing when I bring the temperature up.
- I scanned it with a SnapOn Solus Ultra scanner and it is showing two codes. I also checked some of the AC functions but I am not familiar with using the scanner so I did not want to cause any damage by using functions which I am not comfortable with.
- Tried to add refrigerant but the cans gauge was pointing red.
- Checked the AC pressure.

The pressure readings are as follows: (pretty much the same with AC off, the low was at 110 PSI)

Low pressure: 105 PSI
High Pressure: 110 PSI

Here is a link to the scanner tests pic:
https://imgur.com/a/rA4054g

2. While driving, the dashboard is displaying a message. It has been showing for a while.
- sometimes it's showing in yellow color and the message is "Stop vehicle. Shift to "P". Leave engine running."
- other times (very rarely) it is switching to a red color and says "Stop vehicle. See operator's manual"

Link to message pics:
https://imgur.com/a/LjxOujn

Here are all the codes that the scanner showed:

### Overhead Control Panel
- B181E-64: The Sensor For The Engine Hood Has A Malfunction. There is an implausible signal. - Stored.
- B1F45-00: The Starter Battery Has Excessive Resistance. There Is A General Failure. - Stored.
- B210C-13: The Power Supply Is Outside The Valid Range. There Is An Open Circuit. - Stored.

### Air Conditioning
- B107D-15: The Additional Coolant Pump Has A Malfunction. There Is A Short Circuit To Positive Or An Open Circuit. - Stored.
- B10A2-07: The Actuator Motor For The Left Blend Air Flap Has A Malfunction. There Is A Mechanical Fault. - Stored.

### Dimming Inside Rear View Mirror
- (The same codes as listed under "Overhead Control Panel")

### Headlamp - Left
- U0132-00: Communication With Control Unit Suspension Has A Malfunction. There Is A General Failure. - Stored.

### Panoramic Sliding Roof
- U0168-87: Communication with the electronic ignition lock has a malfunction. The message is missing. - Stored.

### Signal Acquisition Modules: SAM Module - Front
- (The same codes as listed under "Overhead Control Panel")

### Signal Acquisition Modules: SAM Module - Rear
- B1F25-15: The Output For Warning / Ambient Lamp Lift Gate Has A Malfunction. There Is A Short Circuit To Positive Or An Open Circuit. - Stored.
- B1F38-13: The Output For Switch And Controls Illumination Emergency Trunk Lid Release Has A Malfunction. There Is An Open Circuit. - Stored.

### Steering Column Module
- P172A-29: The Direct Select Lever Has A Malfunction. The Signal Is Invalid. - Stored.

### Engine
- P0597-00: The coolant thermostat has an electrical fault or open circuit. There Is A General Failure. - Stored.
- P06DA-00: The actuation of the valve of the oil pump in the combustion engine has an electrical fault or open circuit. There Is A General Failure. - Current, Pending.
- P0563-00: The On-Board Power Supply Voltage Is Too High. There Is A General Failure. - Stored.

### Antilock Brakes
- C100B-77: The Electric Parking Brake Has A Malfunction. The commanded position cannot be reached. - Stored.
- C100B-FA: The Electric Parking Brake Has A Malfunction. - Stored.
- C100B-FF: The Electric Parking Brake Has A Malfunction. - Current, Pending, Stored.

### Electronic Power Steering
- B210F-00: Input 'Circuit 30' Has A Malfunction. There Is A General Failure. - Stored.

I would really appreciate your help in troubleshooting these two issues.

 

Good job doing homework - Your car is trying to get your attention with scary dashboard messages and the dealer wants your paycheck to get A/C working.


Your list of faults is actually a very mild case of low voltage where the system battery is reported bad.

Knowing the battery is questionable, you shouldn't rush to buy another one: TEST ALT. OUTPUT.


You need to know why is the chassis voltage poor:
Drained by parking or by driving ?
​​​​​​
For now, use a CTEK smart charger to charge as per user manual instructions.

Don't disregard the computer message asking to stop driving. Your electric power steering has transient issues.

Use the scanner to reset your faulty modules and then rescan.


Once we have that under control we can figure out why you have too much refrigerant: 100psi all around cold. Lower would be more efficient at creating a pressure difference.
​​​​​​

 

Do you own that scanner? If not, get one specifically for Mercedes: LAUNCH Creader Elite 2.0 BENZ (~$160 on Amazon). Learn how to use it.

You've recorded all of your codes. Clear them. See which ones return. All of them could be caused by a bad or failing battery. Best to replace the battery with a Genuine Mercedes Battery. If the dealer is gonna screw you, check on FCP Euro for a good quality battery.

A/C pressures are generally universal. However, refrigerant capacities are not. There is a sticker in the engine compartment, usually on the grill brace, that says how much by weight you should use. Not sure a bad battery could be causing your A/C problems, but your low pressure is too high and high is too low. The A/C control module will disable the compressor until you get the problem fixed.

 

Ignore code P06DA-00 (and actually be glad you have it). There is an epic discussion about it and how it should not be repaired.

https://mbworld.org/forums/w212-amg/...solenoids.html

 

Thank you for your comments!

Would the Launch scanner help me find the exact cause of the voltage issue as well as what's causing the AC issue?
If not, would the C4 SDS do this?

 

You know, the truth is... both are excellent options but SDS is not child's play like a $150 Launch handheld.

Handhelds are for quickies everywhere anytime where SDS/Xentry needs time just to boot and the learning curve is not friendly.
So both units are quite complementary.

Start with a LAUNCH to make easy progress without getting nose bleeds.