[Solved] Bmw E90 - Searching for the reasons for the insufficient ventilation

Good day. The problem concerns the car BMW E90. After a long stop in the car, the airflow stopped working. Just a moment after starting, it spun for several seconds, stopped and switched on again. After several such cycles, it "fell silent" completely.

I started to dismantle the cabin filter, hoping that the blower motor just rusted (there was a red coating on the mandrel) and it is enough to manually start and grease it. Unfortunately, these actions did not bring the expected result. I just checked the technical condition of this engine and after connecting it to the car battery it works normally ...

The second circuit in this circuit is a resistor commonly called a hedgehog.
Not having much scope to show off (the resistor in this car, unlike the previous generation e46, unfortunately is not repairable) I ordered used on a well-known auction site.
Unfortunately, the purchase turned out to be a box and the blower on the second resistor still does not work.

With a multimeter, I checked that the "hedgehog" still has 12V. Does anyone have any knowledge what values should be on this thin control cable? Below is a preview photo.


How to determine that this resistor is damaged, not the car's electrical system?


best regards

asdros wrote:

How to determine that this resistor has been damaged

Your deduction is destructive, since you bought a new hedgehog and it still doesn't work, it means it's not a hedgehog.

On a thin wire, the voltage is to change with the speed control on the panel.

Thirdly, it is not e36 that you can play pifko and kebabs during breaks in the car.

Thanks for the answer.

Strumien swiadomosci swia wrote:

Your deduction is destructive, since you bought a new hedgehog and it still doesn't work, it means it's not a hedgehog.

I will skip this ad personam right away and I will say about the resistor that it is used (the opposite of the new one) and maybe it was behind the seller and he had no way to check it. I can only suppose that if my blower on the previous resistance showed typical signs of wear.

Secondly, tomorrow I will check this voltage on a thin wire and let you know what the situation looks like when it regulates the rotation on the panel.


As for the last one, I'm not sure the meaning of your allusion. Do you mean that problem solving is so crude? Well, I am an amateur in the field of car electrics, but I believe that thanks to the help of professionals I am able to solve this problem.

Check the blower for rated power, i.e. if it is exceeded, the hedgehog controller does not want it. Let someone do it right, because the spinning connected to the battery on the snout is not important. In addition, it is forbidden to do so and you can burn it to the end. Cyclical stops at equal intervals are a sign of a hedgehog controller efficiency.

So I tried to collect some measurements and it turned out that the blower motor has 0.7 ?.

Then I checked the incoming voltage in the plug reaching the resistor, which was disconnected from the rest ... And so I obtained the following results:
1) voltage in the red cable 11.94 V
2) voltage in the control cable with 0.09 mV airflow adjustment panel turned off
3) voltage in the control cable at a maximum airflow setting of 0.12 mV


Then I made the same measurements with a resistance connected:
1) 11.89 V
2) 11.86 V
3) 11.83 V

There should be a PWM signal in the control cable, why is it different for me?


How to take further diagnostics?

I diagnosed the problem when I dismantled the climatronic panel and looked at it closely. On the path, in the place of defect, a patina raid occurred and the electronics settled the matter. Both resistors and blower are functional.