1991 Audi Coupe Quattro Power Seat Tune up and Repair
The power seats were getting lazy and the driver's side didn't work in Memory mode, so I decided to see what was going on. After 19 years the lubricants have pretty much dried up and hardened into glop, so at the very least they both needed a good lube job.
Tools you will need:
Fiche 72 of the Audi Service Manual: Audi B3 Service Manual - Audi20v.net. BTW, I opened EVERY page there and "Saved to pdf" so that I have the entire manual on my hard drive. Print out the applicable pages, especially the exploded view of the seat. I will post a few images here but you may need the entire section, depending on what you find wrong with your seats.
High quality spray lubricant. I chose this because it goes on thin and turns to a clear grease, and the reviews are excellent: Wurth HHS 2000.
Silicone spray lube, from the box store.
Electronic contact cleaner - to flush out the switches. Do NOT use brake cleaner or any solvent that will damage rubber and plastic!
Basic hand tools, 13 mm box end wrench for the seat bolts
Cotter pin puller or other pointed hook tool.
Multi-meter and test leads - in case you need to adjust the driver's seat position sensors for the Memory system
Compressed air source and needle air gun.
Long 18 AWG or larger jumper wires and a pair of test leads, each with a standard 1/4 FEMALE spade (flat) terminal on one end (to power the seat when it is out of the car)
Test leads with 1/4 MALE spade connectors on one end (if you have to adjust a sensor)
Quick set epoxy - if you find a broken position sensor.
Narrow nylon wire ties (if you have to remove a seat from the car)
2 feet - 1/2 inch black split wire loom
LOTS of patience!
These three scans from the Service Manual shows the driver's side:
NOTE: Item 36 is the Supply-Voltage Relay. It acts
like a circuit breaker and will trip (open the circuit) if the seat current gets
too high (if there is a fault or the switch is held down too long). It "should"
reset automatically. If you have lost all power to the seat and the fuse is OK,
check this relay!
PASSENGER SEAT
Let's start with the passenger seat since it is way less complicated (no Memory ability, no sensors, fewer wires)...
Run the seat all the way forward and remove the black
plastic rail cover on the inner track. Then run the seat all the way back and
up, using all the switches. The seats are held to the floor by two bolts, hidden
by the plastic covers. Hook the cotter pin tool under the covers and pull them
forward and away. The upper cover is flipped over so you can see the clip that
snaps over the bolt head to hold it in place. Sorry for the out of focus pic!
The rear seat attachments have plastic glides that
slide fore and aft in the steel tracks which are part of the floor structure.
They also are designed to let the seat pivot up in front for easy access. Very
nice! Move the seat back a few inches and let the back rest against the rear
seat cushion. Don't push it too far or you will stress the wires and possibly
run the glides out of the tracks at the back. Grab the front seat belt and latch
it into one of the REAR seat belt clips to hold the seat up. Now you can gather
up all the loose change and trash that has fallen under the seat, and vacuum the
area thoroughly.
View under the passenger seat showing three of the
motors, the flex drive cables and both fore and aft "worm screw" actuators. The other two
actuators are not visible in this pic. The recline motor is hidden inside the backrest.
The large brown connector at the top of the pic is the main power connector,
where the floor harness attaches to the seat. With the seat exposed like this
you can run all the switches and watch the operation of the actuators and
linkages. I suggest that you familiarize yourself with the way stuff works
before proceeding.
This shows one of the actuators that run outside the
seat frame. The outer one is hidden by the carpet trim, the inner is accessible
with no cover. Neither can be seen or reached from underneath the main area (the
pic above this one).
I used brake cleaner sprayed on a rag to clean the screws. It's easy to hold the rag in place and use the seat switches to run the actuators back and forth as needed. Don't trap a finger! I don't recommend spraying directly on the screws since it can make a mess of the carpet... you need to be careful! Lube with the high tech HHS 2000, or whatever you chose. The Hurth lube can be sprayed from a distance pretty accurately, and it penetrates easily and dries to a clear non-staining grease. (It's supposed to be great stuff for sunroofs too.) Lube EVERY pivot or sliding part that you can find. There are lots and they are all pretty dry. Don't spray the tracks or glides yet. Don't zap yourself in the eyes! Safety glasses would be a good idea.
This pic shows the main power cable and the glopped
up inner track. To get the seat moving smoothly it's necessary to clean and lube
both tracks and glides. I used brake cleaner sprayed on a rag to scrub the area,
followed by silicone spray. I'm not sure if the Hurth lube attracts dust, but I
know the silicone doesn't.
When you are finished lubing stuff, pull the seat as far forward as it will go.
Clean and lube the rear section of the tracks.
Note the cable wrap has worn or shifted, exposing the inner wires. This is a
vulnerable item, since it is dragged back and forth on the floor (pretty badly
if the seat is kept low), and passengers kick it. I covered the wires with black
split loom. The 1/2 inch size fits this cable perfectly, but it is a little
small for the driver's side cable.
The seat back actuator is different - it is a circular arrangement that is
accessible as shown here. Run the motor and lube the exposed gear teeth carefully. Excess lube will
just get on the upholstery or floor... Now do the other side of the backrest.
The black cloth cover on this seat was coming loose, so I used contact adhesive
to glue it back. If yours is completely down, now you know why your rear
passengers have been complaining about cold feet - it blocks the vents (see pic
above)!
All fixed and ready for another couple of decades.,
While you are in the area, remove the plastic seat back bushing with a large
Phillips bit or driver. Note the deep wear marks from the steel stop and the
movable hook. Replace the bushing or just rotate the part 90 degrees and
reinstall. This will reduce the slop and movement of the seat back. Don't
let passengers slam the seatbacks to the rear and these bushings won't wear so
fast. Note: the inner bushing is NOT accessible without
removing the seat from the car.
Install the front seat bolts and covers and the inner rail cover and take a break. The driver's side comes next.
DRIVER SEAT
The driver seat is just like the passenger side, except the Memory system complicates access and adds a lot more wires and parts. My Memory was dead fore and aft, so I knew I would need to do some major work. Also the fore/ aft "joystick" switch was almost impossible to use - it required excessive pressure and fiddling to get it to operate, though it worked fine for vertical adjustment... NOTE: The position switches are NOT replaceable except as a complete unit with the complete seat wire harness! I hate to think about finding a good used assembly, and about the price of a new one. I decided to remove the seat completely to see if I could get it all working right.
Remove the rear track cover and the front covers and bolts. Tip the seat back and secure it with the seat belt as before to gain access underneath.
In order to get the seat glides far enough back to clear the tracks, you have to remove the lower harness: the steel and rubber "Adel" clamp, the nylon ties and the four plastic connectors. Remove the 10 mm plastic nut for the clamp, and carefully cut the nylon ties. Disconnect the brown power connector. Unplug the seat heater connector and also the two connectors at the Memory computer. Carefully wiggle and drag the entire harness out of the seat frame and let it lie on the floor.
Push the seat rearward until the glides can be removed from the tracks by lifting vertically. Be careful of the carpet and leather! Remove the seat from the car. A second person is helpful - that sucker is heavy and awkward. Lay it carefully on a table or bench that is protected with cardboard or a rug.
Here is what you should be seeing now. Several
problems were apparent on my driver's seat:
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The steel bracket holding the brown power connector on my seat was bent down and one of the plastic tabs holding the female part to the bracket was broken. The connector MUST be positioned well clear of the floor and any moving parts or it will get screwed up as the seat moves! Mine actually unplugged itself as I ran the seat fully back.
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Each of the three Memory position sensors (the fourth is hidden in the seat back) attaches to one end of its motor and one flex drive cable runs through the center of the black plastic housing. This housing snaps in place onto the motor housing, and the inner cable (which has a square shape there) operates the inside of the sensor. It is just a potentiometer (adjustable resistor). The one for the fore/ aft motor is BROKEN and hanging down. You can see this at the right side of the pic. Compare it to the sensor at the bottom, which is oriented correctly with the "ear" horizontal and parallel to the floor of the car. No doubt a passenger kicked too hard one day....
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The nylon tie securing the fore/aft sensor wires to the motor is missing.
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The fore/ aft actuator screws are dry and a little rusty.
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The rear carpet is completely loose and hanging down, blocking the heater vents.
First I wanted to see if I could fix the fore and aft switch, since that would take a while to locate if it needed to be replaced
To get access to the switch trim fastener, the seat back pivot must be
disconnected on the outboard side of the seat ONLY. Leave the inner one alone!
The plastic cover is held on with three strange Audi fasteners. Each hollow
"rivet" has a flush head push pin that must be removed to free the ears that
hold the part to the steel bracket. The two rear pins can be pushed out using a
small hooked tool - I ended up using a nut pick from the kitchen. The front one
is inaccessible from behind, so I just pulled hard until it came free - one ear
broke off. I used silicone sealer on that part when I reinstalled it.
Remove the clip holding the back part to the seat frame. Pull outward and up and the seat back should move out of the way a little. Lay the seat on its side and support the back so it doesn't stress the other pivot.
Remove the plastic cover and screw holding the trim
piece to the seat frame. Wiggle the piece off the switch assembly. This is TOUGH
because there are four clips that snap around the switch housing, two at the top
and two at the bottom. There is also a small tab at the front lower corner that
clips to a metal tab on the seat - remove the clip. Remove the screws holding
the switch assembly to the seat.
Close-up of the switches. This part can't be opened up with risking damage to
the plastic or the circuit boards. The smaller cover on the left is held on by
two deeply recessed steel rings. I suppose you could cut the cover off and use
silicone sealant to protect the area afterwards....
Since I couldn't open up the housing I decided to try another method. Each
switch "should" have a rubber dust seal around it. The one around the joystick
won't come out but the ones around the others will. I removed one and flushed
the entire housing with about 1/4 can of electronic cleaner. I shot cleaner in
around each boot and worked the switches to get the dirt loosened. I noticed
many black particles draining out of the housing - so I guess this is effective.
I purged all the cleaner out of the housing using compressed air and a needle
type blow gun (made from a sport ball inflator). Make sure it is really dry
inside!
NOTE: You could probably flush the switch housing with it in place, but you would get solvent everywhere and I do not really recommend it.
Since the seat is out of the car, it's necessary to supply 12 volts DC to the motors:
NOTE: the female spade terminal power test leads must plug onto pins 1 and 4 on the brown main
connector under the seat. Connect the other ends to a car battery or benchtop power supply. !!!! TEST THE CONNECTIONS TO
MAKE SURE THE SEAT MOVES CORRECTLY !!!! If the seat moves backwards,
reverse the connections. You won't damage anything with reversed connections,
but it will certainly screw up sensor adjustments!
With the seat powered up, try all the switches and check everything out. I discovered that the joystick was now working nicely. Hooray! That cleaner saved some time and a bunch of cash.
Close-up showing the missing wire tie and the sensor
hanging down. The little internal plastic clips that secure it to the motor
housing are busted. You can move the sensor all over the place with a finger.
The long portion should be positioned 90 degrees higher and (more or less)
parallel with the seat bottom. The oval cutout in the steel seat pan is for
clearance when the seat is fully down.
This is a good sensor in the correct position. The
housing moves a few degrees rotationally, but it is secure.
To adjust the sensor, go to the appropriate section of the Service Manual.
The following is the the procedure for adjusting and repairing the fore and aft
sensor:
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Plug the ohm meter male spade terminal test leads into terminals 2 and 5 of the black computer harness connector.
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Run the seat full forward to its stop using the joy stick switch.
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Check the resistance - should be "about" 3780 ohms. Obviously mine was wrong because the stupid housing was busted.
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Holding the housing onto the motor, run the seat back and forth as needed to obtain the correct resistance. Don't crush your fingers.....
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Pull the sensor housing away from the motor and run the seat full forward.
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Place the sensor back on the motor and recheck the resistance!
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While holding the sensor securely on the motor and the long arm roughly parallel to the seat bottom, run the seat full back for easy access.
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Clean the parts well using contact cleaner.
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Glue the sensor onto the housing with quick-set epoxy. I put a LITTLE inside the cavity, and a lot on the outside. You definitely do not want to get glue on the inside moving part or the driveshaft. I secured the sensor using a wooden clothes pin clipped to the flex cable until the epoxy set up (10 minutes).
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RECHECK THE RESISTANCE at the full forward position. If it is wrong, you can still get the sensor loose and repositioned at this time. Be sure to pry off the half-hard epoxy before re-gluing.
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Turn the seat over and epoxy the reverse side.
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If you are happy with the results, pat yourself on the back and go away for a break. I decided to add a thick layer of clear silicone sealer on top of the epoxy as added protection. This part is really vulnerable to kicks from the rear seat passenger.
Now is the time to put the switches back and reassemble everything and then clean and lube the heck out of all the moving parts. Use the jumper wires to check operation and make sure nothing is rubbing or hitting where it shouldn't. Secure all wiring with nylon ties.
Re-glue the rear cloth trim piece if it has come loose.
I bent the brown power connector bracket so that it cleared all moving parts, and I used a 1/8 inch wide nylon tie to secure it to the bracket where the tab had broken off.
Since the OEM wire ties that hold the harness to the seat pan were cut, you need to thread a new narrow tie through each base before taking the seat to the car.
Clean and lube the seat tracks and reinstall the seat. Wear gloves and be careful because there is now a lot of fresh grease.
After getting the wire harness routed, plugged in and secured, run the seat controls to double check that nothing rubs. Put a piece of split loom on the wire harness. The 1/2 inch is a little small here, but it will work OK and it can't fall off.
All finished! The repaired sensor is visible at the
bottom of the pic.
Install the seat bolts and plastic covers.
My seat Memory and switches worked perfectly and I was really pleased! The lubricants stink pretty badly, so park the car with the windows down for a few days if possible.
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New Nov 05, 2009 |