Apparently the blower motors in our cars are driven in an archaic manner by putting resistors in series with the motor where the resistor can consume quite a bit of power.
My cars blower motor just quit. It took me several hours to get it out from under the glove box. It was rather hot, I do not have air conditioning in the garage (16 apartment building) and no WiFi down there so i had to go up occasionally to google stuff.
Anyhow, I got the assembly removed and hooked up the motor to my 24V up to 5A adjustable power supply and (at 12V) it drew more than 5A and the motor works. So I think that the controller for the motor has kicked the bucket.
Doing further research I stumbled upon this thread.
https://www.benzworld.org/forums/w21...make-your.html
Where the guy builds a circuit to trigger a mosfet. Apparently the car feeds different voltages to the circuit (up to 6 Volts) and the motor driver circuit uses some fets and resistors to drive the motor. So my car may not be as inefficient as I had thought. Though seeing only 2 power connection and 2 signal connections did give me an "oh shayté!" moment thinking that the module had a canbus slave inside that would require the purchase of an original part (or spend hours reading the codes sent to the module trying to interpret the messages).
I am slightly more comfortable using micro controllers. I already have several hundred arduinos with a bunch of sensors etc (some mare deployed around the house and I teach with them). And the car is dismantled at the moment and I would like to get it to working order asap before the wife starts yapping about the state of the car and the lack of AC.
So i am thinking about using a voltage divider to scale down the input voltage to 0-5 volts so I can sense what the car controls desire. Then use mosfets to drive the blower motor. More precisely this cheapo circuit with 4 mosfets:
https://www.aliexpress.com/item/Four...ceBeautifyAB=0
Since I already have the board there, might as well use all 4 of the mosfets to power the motor so that cheapo components share the load and do not over heat.
Does anyone see any faults with my logic? Tomorrow morning I shall check the voltage output of the car for myself to determine the voltage levels (to check if there are model year discrepancies). On Thursday I should be able to build the circuit and perform some tests.