Clearing HEVAC faults

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Originally Posted by p38arover

When you reassembled the blend motors, did you align the arrows?

You can see them here: Blend Motor Diagnosis and Replacement

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In the end, no. I did at first before realizing the slots in new potentiometers were about 90 deg out so I set the midrange of the potentiometer travel to the mid range of the wider part of the other gear.

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Originally Posted by TheTree

I too have experienced mayhem with the recirculation motors !


Now the chequebook symbol comes and goes with the weather !!! The flap opens and closes properly so I am suspecting some kind of overrun error but I can live with it for now


Steve

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Steve, maybe try getting hold of a Nanocom and calibrate the servos. Then they shouldn't over-run I would have thought.

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Originally Posted by zzsteve

Yes,actually.
The RC servos are just high-torque radio controlled model servos with ball bearings. Great price/performance ratio compared to a set of blend motors! The ally box is one of the 30 amp PWM controlled drivers for a blower motor. ~$12 on eBay.The knob on the front is what I plan to mount on a panel where the HEVAC control/display now lives (temporarily). I had temperamental recirc motors too, so have locked them in the recirc position and drive the blower motors directly now. I am gradually de-Valeoing the system and will continue until I have chequebook-free zone. Couple of pics attached to show the servo mounting scheme on the heater box and a blower controller.
Cheers,
Steve

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Haha Good guess. That PWM unit is cool, wish I found that when I was dodgeying up the boost controller on my race car. Also I wonder if it would drive an extra injector for a turbo P38? Those servos are a neat fit too.

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Originally Posted by HowdyP38

Steve, maybe try getting hold of a Nanocom and calibrate the servos. Then they shouldn't over-run I would have thought.

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I own a nanocom and tried calibrating the servos but it did not seem to make any difference :(

Thanks anyway mate !

Steve

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Originally Posted by TheTree

I own a nanocom and tried calibrating the servos but it did not seem to make any difference :(

Thanks anyway mate !

Steve

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There is a 'calibration' cycle of distribution and blend motors on every power-up. The HEVAC looks for the end stop positions by looking for a current peak in each drive direction. This sets its limits in firmware. It maybe why electrically noisy pots and/or motors just won't calibrate even if they test OK on the bench. A Nanocom calibration might seek these limits too, but more importantly I think it maps the distribution motor positions with respect to the limit positions so that airflow to face, feet and screen etc... is correct.
Watch those replacement pots. There are two models, different by one letter in the part no. and the only difference is - the slot is 90 degrees away.
HTH
cheers,
Steve

Quote:

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Originally Posted by zzsteve

There is a 'calibration' cycle of distribution and blend motors on every power-up. The HEVAC looks for the end stop positions by looking for a current peak in each drive direction. This sets its limits in firmware. It maybe why electrically noisy pots and/or motors just won't calibrate even if they test OK on the bench. A Nanocom calibration might seek these limits too, but more importantly I think it maps the distribution motor positions with respect to the limit positions so that airflow to face, feet and screen etc... is correct.
Watch those replacement pots. There are two models, different by one letter in the part no. and the only difference is - the slot is 90 degrees away.
HTH
cheers,
Steve

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Hi Mate

These are the Reticulation/Recirculation motors which are attached the the blowers and control the fresh air flaps under the pollen filters. There is no mention of these specifically in the nanocom but one would imagine they are calibrated as well when the other motors are

They are also a different motor, 2 wire instead of 3 wire.

Given the extreme difficulty in accessing these bastards, I am happy to live with the occasional cheque book on the display !

Steve

I just noticed that the gears for these motors are now available [bigrolf]

HVAC Air Conditioning Recirculation Servo Gear Motor For Range Rover P38 SAAB | eBay

Steve