If you pick an older luxury car the two main things near certain: the first is which it can have Power seat flexible shaft, along with the second is the fact that a minumum of one of your seat functions won’t work! Now how hard is it to fix a defective leccy seat? Obviously this will depend a good deal on what the specific problem is along with the car in question, but being a guide let’s have a look at fixing the seats inside an E23 1985 BMW 735i. The seat architecture in other cars will be different, but when you don’t have idea where you’d even commence to fix this kind of problem, this story is certain to be useful for you.
The leading seats from the BMW are amongst the most complex that you’ll get in any older car. They may have electric adjustment for front/back travel, front of the seat up/down, rear in the seat up/down, head restraint up/down and backrest rake forwards/backwards. However, they don’t have electric lumbar adjust and so they don’t have airbags. (When the seats that you will be taking care of have airbags, you need to look at the factory workshop manual to ascertain the safe procedure for focusing on the seats.)
The seat functions are common controlled with this complex switchgear, that is duplicated in the passenger side in the car. As is visible here, the driver’s seat even offers three position memories. Incidentally, the rear seat is additionally electric, having an individual reclining function for every single side! However in this car, your back seat was working all right.
The driver’s seat had three problems.
The button which moved the seat rearwards didn’t work. However, the seat might be moved backwards with one of the memory keys.
The front side from the seat couldn’t be raised.
The top restraint wouldn’t move up or down, although in cases like this the motor may be heard whirring uselessly whenever the proper buttons were pressed.
Having the Seat Out
The first step ended up being to eliminate the seat through the car to ensure entry to every one of the bits might be gained. The seat was electrically moved forward and then the two rear floor-mounting bolts undone.
But exactly how was access will be gained on the front mounting bolts? Pressing the adjustment button didn’t increase the risk for seat to go backwards, and also by this stage the memory button had stopped allowing that action also! The best solution was to manually apply ability to the seat to activate the motor. Every one of the connecting plugs were undone and others plugs containing the heaviest cables inspected. (You will see wiring for seat position transducers and things like that within the loom, nevertheless the motors will likely be powered by noticeably heavier cables.)
Employing a heavy-duty, over-current protected, 12V power supply (that one was made very cheaply – see DIY Budget 12-volt Bench Supply), power was applied to pairs of terminals connecting to the thick wires till the right connections were found. The seat was then powered backwards till the front mounting bolts could possibly be accessed. These were removed and so the Power seat flexible shaft moved forward until it sat in the center of its tracks, making it simpler to get rid of the vehicle.
Fixing the pinnacle Restraint
This is just what the BMW seat looks like underneath. Four electric motors can be seen, plus there’s a fifth within the backrest. Each motor unit connects to some sheathed, flexible drive cable that consequently connects into a reduction gearbox. As I later discovered, inside each gearbox is actually a worm that drives a plastic gearwheel, which actually drives a pinion operating on the rack. At this time, though, an easy test could be created from each motor by connecting capability to its wiring plug and being sure that the function worked mainly because it should. Every function nevertheless the head restraint up/down worked, hence the problems besides the top restraint showed that they have to be in the switches, not the motors or associated drive systems. So how to fix your head restraint up/down movement?
The back trim panel in the seat came off from the simple undoing of four screws. Similar to one other seat motors, the mechanism was made up of a brush-type DC motor driving a versatile cable that went along to the adjust mechanism. The motor worked fine with power connected, although the head restraint didn’t move. Feeling the outside of the drive cable sheath revealed that the drive cable inside was turning, so the problem must lie from the mechanism closest to the pinnacle restraint itself.
The adjustment mechanism was located in place with one screw, which had been accessible with all the leather upholstery disengaged from small metal spikes that held it in place. The legs of the head restraint clipped into plastic cups around the mechanism (one is arrowed here) and those were able to be popped by helping cover their the careful use of a screwdriver.
The full upper section of the adjustment mechanism was then able to be lifted out of the seat back and placed near the seat. Keep in mind that the electrical motor stayed in place – it didn’t have to be removed as well.
To discover what was occurring inside of the unit, it should be pulled apart. It was obviously never built to be repairable, and so the first disassembly step involved drilling the rivets which held the plastic sliders in position on his or her track. With one of these out, the action of the pinion (a small gear) about the rack (a toothed metal strip) may be assessed. Neither looked particularly worn and applying power to the motor indicated that the truth is the pinion wasn’t turning. So that resulted in the trouble was inside of the gearbox itself.
The gearbox was held combined with four screws, each by having an oddly-shaped internal socket head that I don’t use a tool. However, understanding that I could possibly always find replacement small bolts, I used a pair of Vicegrips to undo them – that may be, it didn’t matter should they got a little mutilated during this process of disassembly.
Within the gearbox the worm drive and its particular associated plastic gear could possibly be seen. Initially I was thinking the plastic cog should have stripped, but inspection revealed that this wasn’t the case. So why wasn’t drive getting away from the gearbox? Again I applied power to the motor and watched what happened. The Things I found was even though the cable could possibly be heard rotating inside its sheath, that drive wasn’t reaching the worm. Pulling the worm gear out and inspecting the square-section drive cable demonstrated that the conclusion from the cable had been a little worn and it was slipping back from the drive hole of your worm. (The slippage was occurring in the area marked with the arrow.)
The fix was dead-easy – simply pull the drive cable out of your sheath a little bit, crimp a spring steel washer upon it (backed with a plain washer that here is out of sight – it’s fallen back into the mouth in the sheath) and then push the drive cable back down in its sleeve. Using the crimped washer preventing the worn portion of the cable from sliding back out of your square drive recess inside the worm, drive was restored for the gearbox.
The mechanism could then be reassembled. New screws were utilised to switch the Vicegripped ones, even though the drilled-out rivets were also substituted with new screws and nuts (arrowed). The gearbox was re-greased before assembly and a smear of grease was positioned on the tracks that the nylon sleeves run using. Back in the seat, the mechanism dexqpky30 checked by making use of power – and worked fine.
So in such a case the fix cost nearly nothing, except some time.
Since every one of the motors had now been became in working order, fixing the electrical rearwards travel and front up/down motion could basically be achieved with all the seat in the car – it looked just as if it would have to be a wiring loom or switchgear problem. But even though the seat was out, it made sense to wipe over all the tracks and exposed cogs and re-grease them.
Fixing the remainder
Within the driver’s seat is really a control Power seat switch both relays and also the seat memory facility. Close inspection of the plugs and sockets on the device and also the associated loom indicated that some corrosion had occurred. (Perhaps at some stage a drink had been spilled onto it.) The corrosion showed itself as being a green deposit in the pins plus some tedious but careful scraping with a small flat-bladed screwdriver removed it. Once which had been done, the associated plug was inserted and pulled out 20-30 times to scrape away from the deposit inside the pins of the plug, that have been otherwise impossible to gain access to to completely clean.
At commercial rates, fixing the seat could have cost a lot of money – within labour time and in a complete replacement head restraint up/down mechanism. Nobody will have bothered repairing the gearbox drive – they’d have just replaced everything. The corroded pins? That could have been cheaper, nevertheless the total bill could have still been prohibitive.