If you pick an older luxury car there are 2 things near certain: the initial one is that this may have Power seat flexible shaft, as well as the second is the fact a minumum of one of your seat functions won’t work! So how hard is it to correct a defective leccy seat? Obviously it all depends a great deal on which the exact issue is and also the car in question, but as a guide let’s have a look at fixing the seats within an E23 1985 BMW 735i. The seat architecture in other cars may vary, however if you don’t possess idea where you’d even begin to fix such a problem, this story will certainly be appropriate to you personally.
The leading seats within the BMW are one of the most complex that you’ll discover in any older car. They may have electric adjustment for front/back travel, front from the seat up/down, rear of the 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 the event the seats you are working on have airbags, you should browse the factory workshop manual to find out the safe procedure for working on the seats.)
The seat functions are controlled with this complex switchgear, which can be duplicated on the passenger side in the car. As is visible here, the driver’s seat also has three position memories. Incidentally, the rear seat is likewise electric, with an individual reclining function for each and every side! However in this car, the back seat was working just great.
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 from the seat couldn’t be raised.
The pinnacle restraint wouldn’t move down or up, although in cases like this the motor could possibly be heard whirring uselessly whenever the correct buttons were pressed.
Having the Seat Out
Step one would be to eliminate the seat from your car to ensure that use of each of the bits may be gained. The seat was electrically moved forward and so the two rear floor-mounting bolts undone.
But how was access gonna be gained towards the front mounting bolts? Pressing the adjustment button didn’t increase the risk for seat to advance backwards, and also by this stage the memory button had stopped allowing that action also! The best solution would be 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 find wiring for seat position transducers and such things as that from the loom, however the motors will be powered by noticeably heavier cables.)
Utilizing a heavy duty, over-current protected, 12V power source (this one is made very cheaply – see DIY Budget 12-volt Bench Supply), power was put on pairs of terminals connecting on the thick wires till the right connections were found. The seat was then powered backwards before the front mounting bolts could be accessed. They were removed and so the Power seat motor moved forward until it sat in the midst of its tracks, making it simpler to escape the vehicle.
Fixing your head Restraint
This is exactly what the BMW seat seems like underneath. Four electric motors can be viewed, plus there’s a fifth inside of the backrest. Each electric motor connects to a sheathed, flexible drive cable that therefore connects to some reduction gearbox. As I later discovered, inside each gearbox can be a worm that drives a plastic gearwheel, which actually drives a pinion operating with a rack. At this time, though, a simple test might be made from each motor by connecting power to its wiring plug and ensuring that the function worked because it should. Every function nevertheless the head restraint up/down worked, so the problems aside from the top restraint showed that they must stay in the switches, not the motors or associated drive systems. So how to solve the top restraint up/down movement?
The back trim panel from the seat came off from the simple undoing of four screws. Much like other seat motors, the mechanism was made up of a brush-type DC motor driving a versatile cable that went to the adjust mechanism. The motor worked fine with power connected, although the head restraint didn’t move. Feeling the beyond the drive cable sheath revealed that the drive cable inside was turning, hence the problem must lie inside the mechanism nearest to your head restraint itself.
The adjustment mechanism was kept in place with one screw, that was accessible with the leather upholstery disengaged from small metal spikes that held it in position. The legs in the head restraint clipped into plastic cups around the mechanism (the first is arrowed here) and these had the ability to be popped by helping cover their the careful utilization of a screwdriver.
The full upper area of the adjustment mechanism was then capable of being lifted out of your seat back and placed near the seat. Note that the electric motor stayed in place – it didn’t should be removed as well.
To view that which was going on within the unit, it should be pulled apart. It absolutely was obviously never made to be repairable, and so the first disassembly step involved drilling out of the rivets which held the plastic sliders in place on their track. Using these out, the action of the pinion (a tiny gear) about the rack (a toothed metal strip) may be assessed. Neither looked particularly worn and applying power to the motor showed that actually the pinion wasn’t turning. In order that resulted in the problem was inside the gearbox itself.
The gearbox was held along with four screws, each with an oddly-shaped internal socket head where I don’t possess a tool. However, realizing that I could possibly always find replacement small bolts, I used a set of Vicegrips to undo them – which is, it didn’t matter should they got a bit mutilated during this process of disassembly.
Inside of the gearbox the worm drive and its particular associated plastic gear could be seen. Initially I thought that the plastic cog must have stripped, but inspection demonstrated that this wasn’t the case. So just why wasn’t drive getting away from the gearbox? Again I applied capacity to the motor and watched what went down. What I found was while the cable may 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 indicated that the end of your cable was actually a little worn and it also was slipping back out of your drive hole in the worm. (The slippage was occurring inside of the area marked by the arrow.)
The fix was dead-easy – simply pull the drive cable out from the sheath a bit, crimp a spring steel washer into it (backed by a plain washer that here is out of sight – it’s fallen back into the mouth of your sheath) and then push the drive cable down again in its sleeve. With the crimped washer preventing the worn portion of the cable from sliding back from the square drive recess within the worm, drive was restored to the gearbox.
The mechanism could then be reassembled. New screws were utilised to replace the Vicegripped ones, whilst the drilled-out rivets were also replaced with new screws and nuts (arrowed). The gearbox was re-greased before assembly plus a smear of grease was put on the tracks that this nylon sleeves run using. In the seat, the mechanism dexqpky30 checked by using power – and worked fine.
So in this instance the fix cost nearly nothing, except some time.
Since all of the motors had now been became in working order, fixing the electrical rearwards travel and front up/down motion could simply be achieved using the seat back in the car – it looked as if it needed to be a wiring loom or switchgear problem. But whilst the seat was out, it made sense to wipe over all the tracks and exposed cogs and re-grease them.
Fixing the others
Within the driver’s seat is actually a control Power seat switch both relays as well as the seat memory facility. Close inspection of the plugs and sockets on both the machine as well as the associated loom showed that some corrosion had occurred. (Perhaps at some stage a drink was spilled into it.) The corrosion showed itself like a green deposit about 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 off the deposit in the pins of the plug, that were 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 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 would have been cheaper, however the total bill might have still been prohibitive.