If you opt for an older luxury car there are two things near certain: the initial one is which it could have Power seat switch, as well as the second is a minimum of one in the seat functions won’t work! Now how hard will it be to correct a defective leccy seat? Obviously this will depend a whole lot on which the specific concern is and the car involved, but like a guide let’s take a look at fixing the seats within an E23 1985 BMW 735i. The seat architecture in other cars can vary, but if you don’t possess any idea where you’d even commence to fix this sort of problem, this story is certain to be appropriate to you.
The front side seats from the BMW are amongst the most complex that you’ll see in any older car. They may have electric adjustment for front/back travel, front of your seat up/down, rear of your seat up/down, head restraint up/down and backrest rake forwards/backwards. However, they don’t have electric lumbar adjust and they don’t have airbags. (In case the seats that you are currently taking care of have airbags, you have to read the factory workshop manual to ascertain the safe procedure for working on the seats.)
The seat functions are typical controlled from this complex switchgear, which can be duplicated on the passenger side of the car. As is visible here, the driver’s seat also offers three position memories. Incidentally, the rear seat can also be electric, having an individual reclining function for every side! But in this car, the back seat was working perfectly.
The driver’s seat had three problems.
The button which moved the seat rearwards didn’t work. However, the seat could be moved backwards with one of the memory keys.
The leading of your seat couldn’t be raised.
The pinnacle restraint wouldn’t move up or down, although in this case the motor may be heard whirring uselessly whenever the right buttons were pressed.
Obtaining the Seat Out
The initial step would be to remove the seat in the car to ensure usage of all the bits could possibly be gained. The seat was electrically moved forward and then the two rear floor-mounting bolts undone.
So how was access will be gained towards the front mounting bolts? Pressing the adjustment button didn’t result in the seat to maneuver backwards, and through this stage the memory button had stopped allowing that action at the same time! The perfect solution was to manually apply power to the seat to activate the motor. Every one of the connecting plugs were undone and the ones plugs containing the heaviest cables inspected. (There will be wiring for seat position transducers and things like that in the loom, although the motors will probably be powered by noticeably heavier cables.)
Utilizing a heavy duty, over-current protected, 12V power supply (that one was developed very cheaply – see DIY Budget 12-volt Bench Supply), power was used on pairs of terminals connecting towards the thick wires up until the right connections were found. The seat was then powered backwards before the front mounting bolts could be accessed. They were removed and therefore the Power seat flexible shaft moved forward until it sat in the middle of its tracks, making it easier to escape the auto.
Fixing the top Restraint
This is what the BMW seat seems like underneath. Four electric motors can be seen, plus there’s a fifth inside the backrest. Each electric motor connects to a sheathed, flexible drive cable that in turn connects into a reduction gearbox. Because I later discovered, inside each gearbox is a worm that drives a plastic gearwheel, which in turn drives a pinion operating over a rack. During this period, though, a straightforward test could be created from each motor by connecting capability to its wiring plug and being sure that the function worked as it should. Every function however the head restraint up/down worked, hence the problems besides the head restraint showed that they must remain in the switches, not the motors or associated drive systems. So how to fix the pinnacle restraint up/down movement?
The rear trim panel of the seat came off by the simple undoing of four screws. Similar to another seat motors, the mechanism was comprised of a brush-type DC motor driving a flexible type of cable that visited the adjust mechanism. The motor worked fine with power connected, however the head restraint didn’t move. Feeling the away from the drive cable sheath revealed that the drive cable inside was turning, so the problem must lie from the mechanism nearest to your head restraint itself.
The adjustment mechanism was locked in place with one screw, which had been accessible together with the leather upholstery disengaged from small metal spikes that held it set up. The legs of your head restraint clipped into plastic cups in the mechanism (the initial one is arrowed here) which had the ability to be popped by helping cover their the careful usage of a screwdriver.
The complete upper part of the adjustment mechanism was then able to be lifted out of your seat back and placed near the seat. Be aware that the electric motor stayed in place – it didn’t have to be removed too.
To find out that which was occurring inside of the unit, it should be pulled apart. It had been obviously never built to be repairable, and so the first disassembly step involved drilling out of the rivets which held the plastic sliders set up on their track. Using these out, the act of the pinion (a compact gear) around the rack (a toothed metal strip) could be assessed. Neither looked particularly worn and applying capacity to the motor indicated that in reality the pinion wasn’t turning. To ensure that resulted in the issue was within the gearbox itself.
The gearbox was held together with four screws, each with an oddly-shaped internal socket head in which I don’t have got a tool. However, knowing that I really could always find replacement small bolts, I used a pair of Vicegrips to undo them – that is certainly, it didn’t matter should they got a bit mutilated along the way of disassembly.
In the gearbox the worm drive as well as its associated plastic gear could possibly be seen. Initially I was thinking that the plastic cog will need to have stripped, but inspection showed 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 went down. The Things I found was even though cable could be heard rotating inside its sheath, that drive wasn’t arriving at the worm. Pulling the worm gear out and inspecting the square-section drive cable revealed that the end in the cable had been a little worn plus it was slipping back out from the drive hole of your worm. (The slippage was occurring inside the area marked with the arrow.)
The fix was dead-easy – simply pull the drive cable out of the sheath a bit, crimp a spring steel washer onto it (backed from a plain washer that here is out of sight – it’s fallen into the mouth from the sheath) and then push the drive cable back within its sleeve. Using the crimped washer preventing the worn area 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 utilized to switch the Vicegripped ones, while the drilled-out rivets were also replaced with new screws and nuts (arrowed). The gearbox was re-greased before assembly and a smear of grease was put on the tracks the nylon sleeves run on. In the seat, the mechanism dexqpky30 checked by applying power – and worked fine.
So in cases like this the fix cost nearly nothing, except a little while.
Since every one of the motors had now been turned out to be in working order, fixing the electric rearwards travel and front up/down motion could simply be achieved with all the seat in the car – it looked as if it needed 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.
Under the driver’s seat can be a control Power seat switch both relays and also the seat memory facility. Close inspection from the plugs and sockets on both the system along with the associated loom revealed that some corrosion had occurred. (Perhaps at some stage a drink ended up being spilled onto it.) The corrosion showed itself like a green deposit about the pins and a few tedious but careful scraping with a small flat-bladed screwdriver removed it. Once which was done, the associated plug was inserted and pulled out 20-30 times to scrape away from the deposit in the pins from the plug, that had been otherwise impossible to get into to clean up.
At commercial rates, fixing the seat would have cost several hundred dollars – within labour time as well as in a complete replacement head restraint up/down mechanism. No one would have bothered repairing the gearbox drive – they’d have just replaced the whole thing. The corroded pins? That would have been cheaper, but the total bill might have still been prohibitive.