Ambient temperature sensor BMW e39

I haven’t written anything for a long time, although, to be honest, there were interesting moments, but, alas, I didn’t take pictures, I didn’t write.

I will raise the problem with the temperature sensor overboard BMW 65816905133 E38 E46 E87 E90. The topic is hackneyed and there is a lot of information on it, but there are small nuances that I would like to write about.

Solution of problems.

1) In the ordered it shows -40 degrees

So the sensor is broken. If the sensor is installed, then you must first check it with a multimeter. The resistance of the working sensor should be in the region of 3-5 kOhm. If the multimeter shows infinite or too high resistance (hundreds of kΩ), then the sensor is faulty and should be replaced.

Then check the condition of the wires at the place where the chip is attached, the wires may have frayed or broken.

2) The order indicated +50 degrees.

Occurs in case of a short circuit in the cables going to the sensor, or a short circuit inside the sensor (a very common case when using Chinese sensors). Check the sensor with a multimeter and if its resistance is close to zero, you can try to revive this sensor. There is such a short circuit, as I already wrote on Chinese sensors, due to the fact that the contacts can sink into the sensor housing. Take thin pliers and with a little effort pull the contacts to their original position. This is how I reanimated the sensor that was sent to me from aliexpress. Initially, it was working, but after several unsuccessful connections, the contact fuse blew.

3) Tidy shows the wrong temperature, too low.

This happens due to corrosion of the wires or oxidation of the sensor contacts. Clean the contacts on the chip with a needle, and also check the wires. Replace the chip if possible. The old chip can be soldered to the wires, the main thing is to disassemble it correctly and reassemble it.

Which sensor to choose.

The overboard temperature sensor is an ordinary and cheap thermistor molded in a plastic case, and if the old originals had a copper or brass tip that allows you to quickly transfer heat to the thermoelement, then the new sensors are not much different from Chinese production, moreover, I will not be surprised if in car dealerships Chinese sensors will be sold at the price of originals. Agree, it’s profitable - I bought it for a dollar, and sold it for 10. Therefore, I will offer several rational options for choosing a sensor.

• You buy a thermistor at a radio market.

If you want to do this as cheaply and quickly as possible, just find almost any 4,7 kΩ thermistor in the radio store. You can read more about the thermistor here. The big advantage of this solution is that you don't have to look for chips if you don't have them (sliced ​​with meat). In addition, the design decision on where to mount it is up to you, allowing you to place the thermistor in any convenient location, meaning you no longer need to change the sensor.

• Buying a Chinese sensor.

As I already wrote, contacts are sometimes located on such sensors, which leads to +50 overboard. The main thing here is to insert it very carefully into the chip. The thermistor is a solid part, the sensor housing is very decent, but the Chinese have not learned how to make reliable contacts. In my case, I chose just such a solution, but I could not find the place to connect the sensor to the bumper. Therefore, I fixed it on the screed in a safer place for the sensor. Verified link to aliexpress.

• Buying an old original.

It was the original with a copper or brass tip. When buying, you should take a multimeter to check the sensor. I think you won't notice much difference with an aftermarket or thermistor.

Important! The resistance of a thermocouple changes quite quickly. It is enough to take the sensor in your hand, as it immediately changes its resistance. But being installed in the car, for some reason, the orderly does not want to display changes so quickly and dynamically. This is probably due to the frequency of the survey and an attempt to average the readings so that the temperature does not change each time it passes through the heating network or other heat sources. Therefore, after installing the sensor, the temperature will be -40 degrees, and you need to wait 1-2 hours until the temperature returns to normal.

Important! If you drive in the summer with a temperature of -40 degrees, then you have heated mirrors and washer nozzles at full power. This can damage the heaters of these elements! It is worth noting that the heating of mirrors and nozzles also works in hot weather. Somewhere in the manual for the operation and maintenance of the car there is a plate that indicates how long the heating works in certain temperature ranges. See also: Gazelle 322132 technical specifications