ECC climate control damper motor disassembly and testing

[jreed]

After removing and cleaning the position feedback sensors in three of the ECC damper motors on my '97 855 GLT (~160k miles) a few weeks ago, I was happy to report that the ECC climate control codes cleared themselves and the "mystery of the blinking lights" on the AC control panel had been solved. Or so I thought.
All was well for a couple of weeks and then the AC and REC lights started blinking again. I used the little code reader ( see post below for details on the code reader ) to extract "3 2 3" from the unit, indicating Ventilation Damper Motor Active Too Long. The ventilation damper motor (Volvo part number 6811583) is on the driver's side farthest from the firewall.

My write-up from a couple weeks ago on reading the codes from the ECC on a '97 with OBD2, and cleaning the feedback sensors:
https://www.matthewsvolvosite.com/forums ... 25&start=0

So, it was back into the system again to remove, clean, test and reinstall the ventilation damper motor:
First, I opened up the under-dash area by removing the plastic panel (3 screws, T25) and the metal knee bolster (3 nuts, 13mm) and removed the three T15 screws holding in the damper motor. The ventilation damper motor has an outer white plastic gear that has to be removed to access the insides -- mark the position of this gear with a pen so you can put it back in the right orientation.
Then I marked the position of the shaft relative to the case and removed the three phillips screws holding the case in place. The plastic flaps on my motor were already broken because I had opened this damper up once before (see post above) to clean the position feedback sensor area.
The picture below shows the top side of the circuit board after lifting the gear wheel out. Be sure to mark the relative rotary position of the center wheel so you can re-install it later at the proper position.

After unscrewing and removing the top case of the damper motor

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Then you lift the circuit board out of the bottom half of the case. This reveals the motor, the three reduction gears and old grease underneath:

Lift out the circuit board from the bottom half of the case

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Then you can lift out the three gears one at a time (starting with the white gear on the right since it's at the top of the stack) and clean all the old grease off. I used a nylon bristle brush and some hexane solvent.

Gear removal and relative position of the gears

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Next I tested the motor with a 9V battery by connecting the battery directly to the two connecting pins at the far edge of the circuit board. These pins run directly on the circuit board to the two motor leads. The motor spins quickly and freely in both directions (reverse the polarity of the 9V battery to test both directions).

Testing the motor with a 9V battery (no gears)

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All seemed to be well as far as I could tell (no broken gears, motor turning freely and quietly in both directions) so I reassembled the three gears (moving from left to right: yellow first, then green and finally white) with a little bit of fresh white lithium grease, installed the motor and put the circuit board back in the case. At this point you can again apply the 9V battery to the two solder pads at the edge of the circuit board to test the operation of the motor and gears together:

Testing the motor plus gears in the partially reassembled motor damper.

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On my damper, with a 9V battery, it takes ~3 seconds for the final gear to make a complete rotation. I'm sure this time would be shorter with the full ~13V supply in the car.

Then put the center wheel back in the hole, aligning the clocking marks so that the gear is in the same position as when you removed it from the car (this avoids the time and trouble of having to initialize and re-teach the ECC unit how to control the damper motor):

Center wheel reinstalled, aligned to marks made before removal

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Then you put the top half of the case back on, install the three phillips screws and install the outer gear if you have one. The damper motor for the ventilation damper has an outer gear but some of the others don't have it.

I also made a little video clip showing the testing of the motor and gear train:


After reinstalling the damper motor back in place in the car and testing the system (setting the air direction knob to various positions to force the damper to actuate) everything seemed to be working well and the blinking lights and the code were cleared.

Good luck! This seems to have fixed the problem and saved me quite a bit over buying a new part (in the $100 to $150 range) or a salvage part ($25-$40).

[BEJinFbk]

Nice writeup - Thanks!