KevinH2000

I'm planning ahead for the summer, and I am studying an air conditioning issue with the goal of fixing it before the heat arrives.

On very hot days (e.g., 90 degrees Fahrenheit/32 Celsius and hotter) it takes about 10 minutes of driving before the air conditioning provides reasonably cold air. For example, the first part of my commute home from work consists of about 5 miles of 25 -35 mph driving. The air conditioning will blow lukewarm air during that part of the drive. When I enter the highway, and drive at 60-70 mph, it does better, but it is not ideal. I purchased a laser thermometer at Harbor Freight and will use it to measure the temperature of the air when I need to use the AC again.

I scanned the car and the scanner showed code B1046. According to my iCarsoft MBII, this code means: Check coding 'Refrigerant" pressure sensor for component B12/2 (Refrigerant pressure and temperature sensor 1). OR Component B12/2 (Refrigerant pressure and temperature sensor 1) or line to component has short circuit. (Refrigerant temperature)

I found what appears to be the refrigerant temperature and pressure sensor on the condenser near the bottom of the front bumper. The wiring harness seems to be OK on it.


I've disconnected the wiring harness from the sensor in this picture. The connector is on the right attached to 3 wires - Blue/Red, Brown/Yellow and Red/White.

My theory is that the defective sensor or wiring between the sensor and the front SAM is preventing the SAM from receiving the signal required to tell the car to run the engine fan at high speed. Therefore, the refrigerant is staying warm until I begin to drive at highway speeds.

The refrigerant temperature and pressure sensor is about $50:

I found this video on YouTube in which a W204 claims he replaced his sensor. Unfortunately, I don't think he used the correct technique and I agree with the commentors that the proper way to replace the sensor requires that the refrigerant be evacuated and recharged. So, it is not a DIY job.

Before I proceed, I have the following questions:
1. Does my theory that the problem with the sensor is affecting the operation of the fan make sense?
2. Will I be able to test the wiring between the sensor and the front SAM by using a multimeter to test continuity. (I think that I can identify the connector in the SAM by matching the wire colors.)
3. If I need to replace the sensor, how much would it cost to have the refrigerant evacuated and recharged?

Thanks in advance.

tkid

1. yes, that makes sense.
2. Yes, since you have it disconnected, and can access the other end, it should be easy to check for continuity.
3. My son recently had to work on his air con, i think he was quoted around $120AUD to empty and then re-charge his air-con system.. ring around for some quotes..

I would first spray some electrical cleaner into the sensor terminals and the cable connector, in case there was some dirty contacts there, and see if it starts to work again on its own, before going ahead with replacement..?

KevinH2000

Thanks for the reply. You were correct about the problem with my super charger pipes. I hope your suggestion about the electrical contact cleaner is correct too. I should be able to check it next weekend.


I found this video in which an ML owner connected a new sensor to the wiring harness. Although he didn't install it in the AC condenser, he was able to see a change in the actual value data using an iCarsoft MBII. This proved that the sensor was defective. I am hesitant to do the same because the problem may be in the wiring harness, and I don't want to potentially waste $50. However, if I have trouble checking connectivity in the wiring harness, I can consider that as an option.