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AC/Heating motors overhaul

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AC/Heating motors overhaul

Postby Isus » Thu Mar 02, 2017 11:18 am

Since I also have the ominous clicking sound coming from the depths of the cockpit, signalling that the AC motors or better to say the gears inside are shot, and I do have a replacement used set, so before I decide to tackle the task of dismantling half of the car, :roll: (Would the responsible engineer please stand up, so I may have a word with him) I wanted to check the condition of the replacement unit.
A dry run showed that they run fine, yet how they would perform with the cable attached no one knows.

The first task is removing the motor from the gear housing by undoing two screws
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After that is done, the white plastic retainer housing has to be removed, simply press the white clips inwards
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OK, now the housing has to be opened, one at the time the four clips holding the upper part of the housing have to be pressed simultaneously inwards and down,
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After the housing has been opened the gears are revealed, the problem lies in the three smaller ones, which are made from plastic. Also, the grease is old and not much is present I'd like a word with the engineer who thought of that. :evil:
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In this gearbox, the first small gear had a few broken teeth at two places. Luckily I figured out that the gears rotate only about 1/4 of a full circle.
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So after marking the damaged areas, the gear is rotated by 180° and put back into the housing, also "a little bit" :mrgreen: of grease is applied.
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After one gearbox is sorted time for the other, in this one the gear that was faulty in the first one is OK, yet the second one which is turned by the motor is damaged. Again rotated by 180°, put back into its place and greased.
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So now the only task left is taking half of the car apart and replacing the the unit.
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Re: AC/Heating motors overhaul

Postby pinino » Sat Mar 04, 2017 4:36 am

Don't waste your time replacing individual gears, find a used BMW stepper and swap the whole set, one half BMW with gear set with one half Alfa with lever and wiring. Take a look at this tutorial:

http://www.alfabb.com/bb/forums/164-168 ... s-r-r.html

See p. 10 for swap of gears. Due to their HVAC software, BMW gears don't get stressed out.
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Re: AC/Heating motors overhaul

Postby Uno » Tue Jan 23, 2018 1:17 pm

Hello toghehrer,

The above referred instruction how to proceed with this stepper motor is very good and helpful.

Due to I need to change this part as well on my 164 I would like to ask if there is some experience around for the Super V6 12v models with this 33 ohm resistance modification.

Is it recommended to do on my car as well?

Regards Uno
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Re: AC/Heating motors overhaul

Postby pinino » Wed Jan 24, 2018 5:15 am

Owners of the Super or "facelift" model seldom report stepper failure, thus the resistor modification that we do with the series I model is probably not necessary in the Super (although it might not hurt). The reason for the improved performance in the Super is due to the reprogramming of the controller to reduce pulsing. Many years ago I found this informative email of an Alfa HVAC engineer:

"While the motors remained the same, there was a change starting in '94 with the AC controller (LCD display). While stationary, the stepper motors receive a periodic pulse from the controller to maintain their relative position. This pulse caused "hammering" on the stepper motor gears and is what ultimately causes the "wear & tear" leading to failure. In '94 the controller was reprogrammed to reduce the pulse frequency by 50% to help improve life expectancy of the gears in the stepper motor. I left employment with Alfa in '96, so I don't know if this change produced the desired improvement."

Two different ways improve gear longevity: 50% fewer pulses OR ca. 30% less power (via resistor mod).
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Re: AC/Heating motors overhaul

Postby Uno » Wed Jan 24, 2018 8:59 am

Hello Pinino,

Thank you very much for your information.

So I am more confident not to rework the stepper assembly - I found, according to its former owner it was unused.

Well the car mechanic which resources I can use, located this stepper assembly as the broken part… I hope he is right, because it seems to be pretty much work…

With best regards
Swen
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Re: AC/Heating motors overhaul

Postby alfa east » Thu Jan 25, 2018 1:58 pm

pinino wrote:Owners of the Super or "facelift" model seldom report stepper failure, thus the resistor modification that we do with the series I model is probably not necessary in the Super (although it might not hurt). The reason for the improved performance in the Super is due to the reprogramming of the controller to reduce pulsing. Many years ago I found this informative email of an Alfa HVAC engineer:

"While the motors remained the same, there was a change starting in '94 with the AC controller (LCD display). While stationary, the stepper motors receive a periodic pulse from the controller to maintain their relative position. This pulse caused "hammering" on the stepper motor gears and is what ultimately causes the "wear & tear" leading to failure. In '94 the controller was reprogrammed to reduce the pulse frequency by 50% to help improve life expectancy of the gears in the stepper motor. I left employment with Alfa in '96, so I don't know if this change produced the desired improvement."

Two different ways improve gear longevity: 50% fewer pulses OR ca. 30% less power (via resistor mod).


Very good and in-depth info. Amazing you could "dig that out"! Thank you for sharing.
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