Low side drivers are easier to make, insulate and more importantly control, you may only need 3.3V signal to turn a low side 12v driver on and off for instance! If you go looking for them you'll find way more low side (0V ground switching) than high side (supply switching). As for PWM duty cycles, as a kid you may have tried to turn your bedroom lights into a disc by turning them on and off quickly (not recommended) well if you turn them on for half a second and off for half a second (50% duty cycle) your bedroom would theoretically be at half brightness, or a motor would run at half speed. The main reason for not using dropper resistors other than the heat dissipation is the motor looses torque at lower speeds due to the lower voltage across its terminals. Switching a maximum voltage on and off quickly while the average measured voltage looks lower the torque is maintained, within limits. Good video, I think the first garage just didn't know what they were doing or didn't want the work. Make it sound expensive and you can either fleece someone or make tham go away! 🤙
Great job and a much easier fix than on the E53 X5. I had to do mine earlier this year and as you're no doubt aware, its a dashboard out job. Still it was the original from 2005 on a car with 250k miles👍
Hi! Good explanation. The reason they are using the ground to control the various devices is due to ability to check the system. As you well stated, when the ground is not applied, you will have a 12v return from the motor (in this case). The control module can check for the "feedback" voltage and determine if there is a problem with the circuit or the motor. In this case it measured the voltage return from the motor and determined there's a problem so it triggered the fault - bad motor. Of course you could have a bad wire/bad connection/bad motor, the module doesn't know that, but at least you have a starting point. If it was 12v+ controlled the module couldn't recieve a feedback, because you can't check for ground return. I mean you can, but would always trigger a fault. The fact that you saw a pwm of low voltage on the ground side could mean a bias voltage sent by the module to pinpoint the problem (motor or connection). If there is no low pwm signal returning it means short circuit. It there is low pwm signal returning it means open circuit and the module can trigger the fault code accordingly. I'm used to this systems from industrial machinery. Of course the price of that systems is 10 times more expensive. It's amazing where the car diagnostic systems have arrived....and people are saying..."too much electronics...it was better before..." yeah right...try diagnosing a car with this much accessories without feedback systems on the modules! Keep them coming! Cheers
In Vantaa, Finland 🙂 Thats really good to hear. Maybe we can do a video together where I can teach a few things, basic tips? Email me 🙂 I want to do different types of videos.
Oh, the blower fan on the E90's will cost you more in chiropractor's visits. A massive PITA to replace with a lot of swearing involved, if you have a wife that does Yoga get her to replace it!
Low side drivers are easier to make, insulate and more importantly control, you may only need 3.3V signal to turn a low side 12v driver on and off for instance! If you go looking for them you'll find way more low side (0V ground switching) than high side (supply switching).
As for PWM duty cycles, as a kid you may have tried to turn your bedroom lights into a disc by turning them on and off quickly (not recommended) well if you turn them on for half a second and off for half a second (50% duty cycle) your bedroom would theoretically be at half brightness, or a motor would run at half speed. The main reason for not using dropper resistors other than the heat dissipation is the motor looses torque at lower speeds due to the lower voltage across its terminals. Switching a maximum voltage on and off quickly while the average measured voltage looks lower the torque is maintained, within limits.
Good video, I think the first garage just didn't know what they were doing or didn't want the work. Make it sound expensive and you can either fleece someone or make tham go away! 🤙
Really interesting explanation Julian and good to understand why they design things this way. Thanks mate 🙂
An excellent instructional video 👍
Thank you Trevor 🙂
Great job and a much easier fix than on the E53 X5. I had to do mine earlier this year and as you're no doubt aware, its a dashboard out job. Still it was the original from 2005 on a car with 250k miles👍
Oh those... 😵💫 I remember them lol. The E53 is a brilliant wagon but that motor is a nightmare. Thanks for watching🙂
👍
SHARP-WITTED,BMW Mechanic AllMech
From Nick Ayivor from London England UK 🇬🇧 ⏰️ 13:54 Good Afternoon
Hi! Good explanation. The reason they are using the ground to control the various devices is due to ability to check the system. As you well stated, when the ground is not applied, you will have a 12v return from the motor (in this case). The control module can check for the "feedback" voltage and determine if there is a problem with the circuit or the motor. In this case it measured the voltage return from the motor and determined there's a problem so it triggered the fault - bad motor. Of course you could have a bad wire/bad connection/bad motor, the module doesn't know that, but at least you have a starting point. If it was 12v+ controlled the module couldn't recieve a feedback, because you can't check for ground return. I mean you can, but would always trigger a fault. The fact that you saw a pwm of low voltage on the ground side could mean a bias voltage sent by the module to pinpoint the problem (motor or connection). If there is no low pwm signal returning it means short circuit. It there is low pwm signal returning it means open circuit and the module can trigger the fault code accordingly. I'm used to this systems from industrial machinery. Of course the price of that systems is 10 times more expensive. It's amazing where the car diagnostic systems have arrived....and people are saying..."too much electronics...it was better before..." yeah right...try diagnosing a car with this much accessories without feedback systems on the modules! Keep them coming! Cheers
Thanks for the explanation Alex 🙂
@@allmech_BMW_fault_finding I'm pretty sure you already knew that, but thanks for the appreciation 😊
@alexdragomirescu5084 Probably but I wouldn't have put the explanation as well as you did, Alex 🙂
Where is your shop? Can I bring my car to you please 😬😬 Came across loads of channel in youtube and yours looks the best.
In Vantaa, Finland 🙂 Thats really good to hear. Maybe we can do a video together where I can teach a few things, basic tips? Email me 🙂 I want to do different types of videos.
Oh, the blower fan on the E90's will cost you more in chiropractor's visits. A massive PITA to replace with a lot of swearing involved, if you have a wife that does Yoga get her to replace it!
Lol. Been a few years but I remember them fondly 🙂