F355 Aircon Recirculation Flap
Discussion
A lovely Easter Monday so my F355 is sat on my driveway in bits with the front boot liner removed to fix the aircon recirculation flap. The usual problem, the plastic bushing from the geared motor to the flap has sheared and there's a brass replacement available from Hill Engineering.
With the motor out and the ignition on, it runs one way normally, press the button and it reverses. What surprises me is that the motor keeps running - it isn't on a timer, there are no limit switches, it simply runs until it stalls and there doesn't seem to be any circuitry to sense the increase in current and shut it off. Does anyone know if this is correct or is the ECU shot? As it is, the motor is running all the time and you'd think it would burn out. With the motor applying torque constantly against the stalled flap, it's no wonder the plastic bush has failed.
The manual simply says the current it draws is about 200mA when running and 500mA when "blocked".
If it turns out the power should be shut off, I'll go and fix the ECU, otherwise I might design a circuit to do the job externally but it would be helpful to know if anyone else has experience of this.
With the motor out and the ignition on, it runs one way normally, press the button and it reverses. What surprises me is that the motor keeps running - it isn't on a timer, there are no limit switches, it simply runs until it stalls and there doesn't seem to be any circuitry to sense the increase in current and shut it off. Does anyone know if this is correct or is the ECU shot? As it is, the motor is running all the time and you'd think it would burn out. With the motor applying torque constantly against the stalled flap, it's no wonder the plastic bush has failed.
The manual simply says the current it draws is about 200mA when running and 500mA when "blocked".
If it turns out the power should be shut off, I'll go and fix the ECU, otherwise I might design a circuit to do the job externally but it would be helpful to know if anyone else has experience of this.
Edited by blueSL on Monday 6th April 15:36
Thanks for confirming that. From an engineering standpoint, it makes no sense at all to leave the flap motor powered and stalled all the time the car engine is running. I expect the prolonged - and quite significant - torque applied to the plastic bushing leads to its failure.
Having taken the ECU apart, there's a microprocessor with the program burned in at manufacture - no flash reprogramming here - and I expect there's a bug in the program which leaves the power on when it should be turned off which was not discovered until the chips had been made.
So, I've designed an add-on circuit which keeps power applied for only 3 seconds when a change in the recirculation is required; I wouldn't have bothered to even repair the flap because I rarely use the button but I then discovered the flap is opened and closed independently under control of the ECU which might help the misting up problem I have.
Having taken the ECU apart, there's a microprocessor with the program burned in at manufacture - no flash reprogramming here - and I expect there's a bug in the program which leaves the power on when it should be turned off which was not discovered until the chips had been made.
So, I've designed an add-on circuit which keeps power applied for only 3 seconds when a change in the recirculation is required; I wouldn't have bothered to even repair the flap because I rarely use the button but I then discovered the flap is opened and closed independently under control of the ECU which might help the misting up problem I have.
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