If you opt for an older luxury car the two main things near certain: the very first is that this can have Power seat motor, along with the second is that at least one of your seat functions won’t work! So how hard will it be to correct a defective leccy seat? Obviously it depends a whole lot on which the actual problem is as well as the car in question, but as being a guide let’s have a look at fixing the seats in an E23 1985 BMW 735i. The seat architecture in other cars can vary, however, if you don’t possess any idea where you’d even start to fix this sort of problem, this story is sure to be appropriate for your needs.
The front seats from the BMW are amongst the most complex that you’ll discover in any older car. They have got electric adjustment for front/back travel, front from 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. (In the event the seats that you are currently working on have airbags, you must look at the factory workshop manual to ascertain the safe procedure for taking care of the seats.)
The seat functions are typical controlled with this complex switchgear, which happens to be duplicated on the passenger side from the car. As is visible here, the driver’s seat also offers three position memories. Incidentally, the back seat is also electric, by having an individual reclining function for every 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 could be moved backwards using one of the memory keys.
The leading of your seat couldn’t be raised.
The head restraint wouldn’t move down or up, although in cases like this the motor might be heard whirring uselessly whenever the best buttons were pressed.
Having the Seat Out
The first task would be to eliminate the seat from the car so that entry to every one of the bits could be gained. The seat was electrically moved forward and then the two rear floor-mounting bolts undone.
So how was access likely to be gained for the front mounting bolts? Pressing the adjustment button didn’t result in the seat to go backwards, and by this stage the memory button had stopped allowing that action also! The solution ended up being to manually apply ability to the seat to activate the motor. All the connecting plugs were undone and those plugs containing the heaviest cables inspected. (There will be wiring for seat position transducers and stuff like that from the loom, although the motors will probably be powered by noticeably heavier cables.)
Employing a durable, over-current protected, 12V power supply (this particular one was made very cheaply – see DIY Budget 12-volt Bench Supply), power was applied to pairs of terminals connecting for the thick wires before the right connections were found. The seat was then powered backwards until the front mounting bolts could possibly be accessed. They were removed and then the Power seat switch moved forward until it sat during its tracks, making it easier to get rid of the car.
Fixing the pinnacle Restraint
This is exactly what the BMW seat appears to be underneath. Four electric motors is seen, plus there’s a fifth inside of the backrest. Each electric motor connects to some sheathed, flexible drive cable that subsequently connects to your reduction gearbox. When I later discovered, inside each gearbox can be a worm that drives a plastic gearwheel, which drives a pinion operating on the rack. During this period, though, a simple test could possibly be made from each motor by connecting power to its wiring plug and being sure that the function worked since it should. Every function however the head restraint up/down worked, therefore the problems besides the pinnacle restraint showed that they must maintain the switches, not the motors or associated drive systems. But just how to solve the top restraint up/down movement?
The back trim panel of the seat came off by the simple undoing of four screws. Much like other seat motors, the mechanism consisted of a brush-type DC motor driving a flexible type of cable that went to the adjust mechanism. The motor worked fine with power connected, however the head restraint didn’t move. Feeling the outside the drive cable sheath established that the drive cable inside was turning, hence the problem must lie in the mechanism closest to the head restraint itself.
The adjustment mechanism was kept in place with one screw, which was accessible with the leather upholstery disengaged from small metal spikes that held it in position. The legs from the head restraint clipped into plastic cups in the mechanism (the initial one is arrowed here) and those could be popped out with the careful use of a screwdriver.
The whole upper section of the adjustment mechanism was then capable of being lifted out of the seat back and placed next to the seat. Remember that the electric motor stayed set up – it didn’t need to be removed at the same time.
To view that which was going on inside of the unit, it needed to be pulled apart. It was actually obviously never created to be repairable, and so the first disassembly step involved drilling out the rivets which held the plastic sliders into position on their own track. With these out, the act of the pinion (a tiny gear) in the rack (a toothed metal strip) may be assessed. Neither looked particularly worn and applying capacity to the motor demonstrated that in reality the pinion wasn’t turning. So that meant the situation was inside of the gearbox itself.
The gearbox was held along with four screws, each with the oddly-shaped internal socket head in which I don’t have got a tool. However, with the knowledge that I could possibly always find replacement small bolts, I used some Vicegrips to undo them – that is certainly, it didn’t matter when they got somewhat mutilated at the same time of disassembly.
Within the gearbox the worm drive and its particular associated plastic gear could possibly be seen. Initially I assumed that the plastic cog need to have stripped, but inspection revealed that this wasn’t the situation. So why wasn’t drive getting away from the gearbox? Again I applied power to the motor and watched what actually transpired. A Few Things I found was even though cable could be heard rotating inside its sheath, that drive wasn’t getting to the worm. Pulling the worm gear out and inspecting the square-section drive cable indicated that the final in the cable was actually a little worn and it was slipping back from the drive hole of your worm. (The slippage was occurring inside the area marked by the arrow.)
The fix was dead-easy – simply pull the drive cable out from the sheath a little bit, crimp a spring steel washer upon it (backed by a plain washer that here has run out of sight – it’s fallen into the mouth from the sheath) then push the drive cable back in the sleeve. With all the crimped washer preventing the worn portion of the cable from sliding back out of the square drive recess in the worm, drive was restored on the gearbox.
The mechanism could then be reassembled. New screws were utilised to change the Vicegripped ones, whilst 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 added to the tracks the nylon sleeves are powered by. In the seat, the mechanism dexqpky30 checked by utilizing power – and worked fine.
So in this instance the fix cost nearly nothing, except a little while.
Since all of the motors had now been turned out to be in working order, fixing the electrical rearwards travel and front up/down motion could simply be achieved with the seat back into the car – it looked just as if it had to be a wiring loom or switchgear problem. But whilst the seat was out, it made sense to wipe total the tracks and exposed cogs and re-grease them.
Fixing the others
Under the driver’s seat is really a control Power seat switch both relays and also the seat memory facility. Close inspection of your plugs and sockets on both the system and the associated loom revealed that some corrosion had occurred. (Perhaps at some stage a drink was spilled onto it.) The corrosion showed itself as being a green deposit about the pins and a few tedious but careful scraping using a small flat-bladed screwdriver removed it. Once that was done, the associated plug was inserted and pulled out 20-30 times to scrape off of the deposit inside the pins of the plug, that had been otherwise impossible to access to clean up.
At commercial rates, fixing the seat would have cost hundreds of dollars – both in labour time and in the complete replacement head restraint up/down mechanism. No-one would 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.