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Dear Pesti,
Good p.m. and may this find you well. I hope you removed the negative battery cable clamp from the battery terminal, and put the clamp in a plastic bag to isolate it, before you removed the seat. Under the driver's seat is the airbag sensor. If it is thumped or whacked - for example, if the chair gets loose and lands on the sensor - it could trigger an airbag deployment. That can be lethal at close quarters and it will be otherwise costly. A replacement airbag is about $1K, and the same is true of the sensor.
The seat malfunction likely is due to a worn end on the drive cable. I append below, a procedure for curing the problem.
Hope this helps. Post back, if you have questions.
Yours faithfully,
spook
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Procedure for Repair of Drive Cables on Power Seats.
I. SEAT REMOVAL.
A. ☞ DEATH DANGER WARNING. To avoid accidental triggering of an airbag - the sensor is under the driver’s seat - remove negative battery cable clamp from the negative battery terminal, and put the clamp in a plastic bag, to ensure that no power can flow to the airbag sensor. An airbag deployment at close quarters can kill; even if it does not, it will be expensive. If an airbag deploys, the airbag and the sensor must be replaced. Each costs about $1,000US.
B. Preparations
1. Cover the inner face of the passenger door panel with a sheet of cardboard. Cover with cardboard, the rocker panel section at the bottom of the door opening and the plastic strip on the interior of that rocker panel section (the door threshold strip). This will protect them against damage. A power seat is heavy, bulky, and unwieldy.
2. Next, remove the plastic covers over the back end of the seat tracks. They are held on by lugs on the tracks, which fit into recesses in the covers. Pull back to disengage the cover from the lug, and then pull up. With a bit of wiggling, they should come free. Be especially gentle, if it is cold, when you do this. Old plastic is always brittle, and cold plastic is even more brittle. Remove the cover on the front door-side track (single Torx-20 screw).
C. Seat Removal
1. Loosen, but do not remove the four seat bolts.
2. To remove the seat belt anchor bolt, unscrew the cup-holder at the front of the seat (a single Torx-20 screw). Rotate the cup-holder upwards, to expose the seat-belt anchor bolt. Remove it. This bolt will be tight: be prepared to use muscle on it. Remove the seat belt from the seat.
3. Remove the four seat bolts.
4. Pull the seat as far back as possible, then move it forward 5mm/ 1/5". That will allow the seat track lug to disengage from the "keyhole" in the floor plan.
5. Carefully lift the seat out of the car.
II. CABLE REMOVAL
A. Position the seat bottom-up on supports (with towel or blanket to protect the upholstery), such that the leading edge of the seat is closest to you. The "leading edge" is that which is against the back of the driver’s or passenger’s knees, and thus the edge closest to the windshield, when the seat is installed.
B. Find the seat motors, a three-unit cluster, mounted towards the seat’s leading edge.
C. To the right of the motor cluster, you will see a black steel bracket, with a “D” shaped hole in it. The round side of the “D” faces the seat’s leading edge .
D. On the underside of that bracket, on the left side of it (i.e., the side closest to the motor cluster) you will find six, 8-mm, hex head, self-tapping screws. These six screws secure the bracket to the motor housings.
E. Use 1/4" socket tools. You will need an 8mm socket, a 4" or 6" spring flex shaft, and a ratchet. Starting from the screw closest to the seat’s leading edge, remove these screws. You can insert the spring flex shaft through the “D” shaped hole to access some of the screws. Note: there is no need to touch the screws at the other end of the black steel bracket, that closest to the seat track.
F. When you remove the screws, you will notice a slight gap (3/16", 3-4 mm) opens up between the bracket edge, and the studs on the motor housings, from which you removed the screws mentioned in (E). Do not be concerned. You will close this gap, when you re-install the screws.
G. You can now remove the drive cable end from any of the three motors, by pulling the black plastic cable housing straight towards the “D” shaped hole in the steel bracket. The end of the drive cable is not secured to the motor housing by a set-screw. You will see that at the motor end of the drive cable, the bright metal cable housing is slightly flared. This flare in the cable housing allows the black steel bracket to snug the end of the drive cable housing, into the motor housing opening, when the bracket’s 6 mounting screws are tightened.
H. If the seat tracks are not aligned, you can align them as follows.
1. Remove the drive cable from its opening in the seat track drive motor (the middle one in the cluster).
2. Supply power to the seat, from a 12-volt battery (or portable 12-volt source) through leads with insulated (red and black flexible plastic), spring-loaded alligator clamps. The wire from the positive pole of the battery/source should go to the spade terminal, for the red wire on the grey connector and the wire from the negative pole of the battery/source should go to spade terminal for the black wire on the grey connector.
3. On a passenger-side powered seat - which does not have “memory” - use a carpenter’s steel framing square (16"x24"). Place the short leg of the square along the outer edge of one of the tracks, with the long leg extending parallel with the leading edge of the seat, until it (the long leg of the carpenter’s square) extends past the track on the other side of the seat.
4. Use the seat switch to advance the powered track, until it just touches the edge of the carpenter’s square. Both seat tracks are now aligned.
On a powered driver’s seat - which memory and its own seat computer - you may need to take the seat to a Volvo dealer, to get the tracks re-aligned, if the method set forth above, does not restore synchronous track movement.
I. Once the motor-end of the drive cable has been removed, you can remove the other end, from the track drive gear mechanism, beside the seat track. You can then replace the cable.
J. In some cases, you can restore function, by pulling the drive cable out of the black plastic housing and reversing the cable, i.e., inserting the end that was closest to the motor, so that it goes into the track drive gear mechanism. This may be worth trying, if the end of the drive cable, that was closest to the motor, is slightly rounded or worn, and if the end, that was closest to the seat drive mechanism, is not rounded or worn. While a slight rounding may stop the motor from turning the drive cable, slight rounding or wear does not seem similarly to affect the drive cable’s capacity to turn the track drive gear.
K. Once you have installed a new drive cable assembly, or reversed the drive cable in its housing, you should test the new assembly.
III. TESTING & RE-INSTALLATION
A. Using your hand, push the end of the track drive cable, into the motor housing, and hold it firmly in place. Use the seat switch to activate the motor. If the tracks (normally bolted to the floor) move smoothly and completely, forwards and backwards, you’ve restored the seat to good working order. You may want to lubricate the tracks with a spray grease (e.g., white lithium). If the seat tracks do not move smoothly and completely, forwards and backwards, check the tracks to ensure they’re free of obstructions (e.g., coins, dirt, debris, etc.) and not bent or otherwise damaged. Clear any obstructions, and re-test. If the tracks are bent, or teeth broken, the tracks will need to be replaced.
B. Reinsert screws into the holes at either end of the black steel bracket, and tighten them “snug”. REMEMBER: these screws are going into plastic, so brute force will strip the hole!!! Tighten the two end screws alternately (rather than doing one completely, and then the other). This alternate tightening will gently and evenly draw the steel bracket towards the motor cluster, pushing the ends of the drive cable housings into the motor housing openings. The four middle screws need not be re-inserted at this point.
C. Re-test any repaired drive mechanism, to ensure it still works through its full range of movement. If it still does so, insert and tighten the remaining four hex head screws. Go GENTLY: these screws are going into plastic studs on the motors, so it is easy to strip a hole.
D. Re-install the seat in the car, by aligning the studs on the seat track bottoms with the holes in the seat pan. When the seat is flat on the floor, move the seat, until the holes at the end of the seat tracks match the holes in the floor pan. Insert the seat bolts and set the threads into the holes, by turning the bolts by hand, counter-clockwise, for one full turn. You should hear/feel a slight “click”, when the thread on the bolt engages the thread in the hole . Hand tighten as much as possible, and then torque to 33 pound/feet (45 nM). Hand tighten and then torque the seat belt anchor bolt to 33 pound/feet (45nM).
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