If you pick an older luxury car the two main things near certain: the initial one is it can have Power seat motor, and the second is the fact one or more of the seat functions won’t work! So how hard will it be to correct a defective leccy seat? Obviously this will depend a lot about what the actual problem is and also the car in question, but as a guide let’s have a look at fixing the seats in an E23 1985 BMW 735i. The seat architecture in other cars varies, however, if you don’t have idea where you’d even commence to fix such a problem, this story will definitely be appropriate for your needs.
The leading seats inside the BMW are one of the most complex that you’ll get in any older car. They have electric adjustment for front/back travel, front from the 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 also don’t have airbags. (If the seats that you are taking care of have airbags, you should see the factory workshop manual to ascertain the safe procedure for taking care of the seats.)
The seat functions are all controlled with this complex switchgear, which happens to be duplicated in the passenger side in the car. As can be seen here, the driver’s seat even offers three position memories. Incidentally, the back seat is also electric, by having an individual reclining function for each side! Nevertheless in this car, the 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 may be moved backwards using one of the memory keys.
The top from the seat couldn’t be raised.
The pinnacle restraint wouldn’t move up or down, although in this instance the motor could be heard whirring uselessly whenever the best buttons were pressed.
Getting the Seat Out
The first step ended up being to remove the seat in the car so that use of every one of the bits might be gained. The seat was electrically moved forward and therefore 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 increase the risk for seat to go backwards, and also this stage the memory button had stopped allowing that action at the same time! The perfect solution would be to manually apply capacity to the seat to activate the motor. Every one of the connecting plugs were undone and people plugs containing the heaviest cables inspected. (You will see wiring for seat position transducers and stuff like that in the loom, nevertheless the motors is going to be powered by noticeably heavier cables.)
Employing a high quality, over-current protected, 12V power supply (this particular one was made very cheaply – see DIY Budget 12-volt Bench Supply), power was put on pairs of terminals connecting towards the thick wires until the right connections were found. The seat was then powered backwards up until the front mounting bolts may be accessed. These were removed and then the Power seat switch moved forward until it sat during its tracks, making it easier to get out of the auto.
Fixing the top Restraint
This is what the BMW seat appears like underneath. Four electric motors can be viewed, plus there’s a fifth inside the backrest. Each electric motor connects to some sheathed, flexible drive cable that subsequently connects to a reduction gearbox. While I later discovered, inside each gearbox is a worm that drives a plastic gearwheel, which actually drives a pinion operating on a rack. At this point, though, a simple test could possibly be manufactured from each motor by connecting capability to its wiring plug and ensuring the function worked mainly because it should. Every function although the head restraint up/down worked, so the problems aside from the top restraint showed that they have to maintain the switches, not the motors or associated drive systems. But just how to correct the top restraint up/down movement?
The back trim panel in the seat came off with the simple undoing of four screws. Similar to the other seat motors, the mechanism consisted 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 outside the drive cable sheath revealed that the drive cable inside was turning, therefore the problem must lie within the mechanism closest to the top restraint itself.
The adjustment mechanism was held in place with one screw, that was accessible using the leather upholstery disengaged from small metal spikes that held it into position. The legs of your head restraint clipped into plastic cups on the mechanism (the initial one is arrowed here) and they 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 capable of being lifted out from the seat back and placed next to the seat. Be aware that the electric motor stayed in place – it didn’t have to be removed also.
To see that which was going on in the unit, it must be pulled apart. It absolutely was obviously never designed to be repairable, so the first disassembly step involved drilling out of the rivets which held the plastic sliders set up on their track. With these out, the act of the pinion (a compact gear) about the rack (a toothed metal strip) could possibly be assessed. Neither looked particularly worn and applying capacity to the motor indicated that in fact the pinion wasn’t turning. So that resulted in the problem was inside the gearbox itself.
The gearbox was held combined with four screws, each with the oddly-shaped internal socket head in which I don’t possess a tool. However, knowing that I was able to always find replacement small bolts, I used a couple of Vicegrips to undo them – that is certainly, it didn’t matter once they got a little mutilated during this process of disassembly.
Within the gearbox the worm drive and its particular associated plastic gear could be seen. Initially I was thinking that this plastic cog need to have stripped, but inspection showed that this wasn’t the truth. So why wasn’t drive getting away from the gearbox? Again I applied capacity to the motor and watched what happened. The Things I found was even though 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 demonstrated that the conclusion in the cable was actually a little worn and it was slipping back from the drive hole of your worm. (The slippage was occurring within the area marked from the arrow.)
The fix was dead-easy – simply pull the drive cable from the sheath a little bit, crimp a spring steel washer on it (backed by a plain washer that here is out of sight – it’s fallen into the mouth in the sheath) and after that push the drive cable back in its sleeve. With the crimped washer preventing the worn section of the cable from sliding back out of the square drive recess from the worm, drive was restored on the gearbox.
The mechanism could then be reassembled. New screws were used 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 plus a smear of grease was positioned on the tracks the nylon sleeves operate on. Back in the seat, the mechanism dexqpky30 checked by applying power – and worked fine.
So in such a case the fix cost nearly nothing, except a while.
Since all of the motors had now been became in working order, fixing the electrical rearwards travel and front up/down motion could basically be achieved using the seat back into the car – it looked like it must be a wiring loom or switchgear problem. But as the seat was out, it made sense to wipe total the tracks and exposed cogs and re-grease them.
Fixing the others
Beneath the driver’s seat is really a control Power seat switch both relays as well as the seat memory facility. Close inspection in the plugs and sockets on both the system and also the associated loom showed that some corrosion had occurred. (Perhaps at some stage a drink was spilled on it.) The corrosion showed itself as a green deposit around the pins and several tedious but careful scraping using 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 inside of the pins in the plug, which were otherwise impossible to access to clean.
At commercial rates, fixing the seat will have cost large sums of money – within labour some time and in the complete replacement head restraint up/down mechanism. No person will have bothered repairing the gearbox drive – they’d have just replaced the whole thing. The corroded pins? That would have been cheaper, however the total bill could have still been prohibitive.