If you buy an older luxury car the two main things near certain: the very first is it could have Power seat motor, along with the second is that at least one in the seat functions won’t work! So, just how hard could it be to correct a defective leccy seat? Obviously it all depends a great deal of what the actual dilemma is as well as the car under consideration, but as being a guide let’s look into fixing the seats inside an E23 1985 BMW 735i. The seat architecture in other cars may vary, but when you don’t have any idea where you’d even learn to fix this kind of problem, this story will certainly be of use for your needs.
The front seats inside the BMW are one of the most complex that you’ll discover in any older car. They already have electric adjustment for front/back travel, front of the seat up/down, rear from 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. (When the seats that you are focusing on have airbags, you have to see the factory workshop manual to find out the safe procedure for working on the seats.)
The seat functions are typical controlled through this complex switchgear, which is duplicated on the passenger side of your car. As is visible here, the driver’s seat also has three position memories. Incidentally, the rear seat is also electric, with the individual reclining function for each and every side! But in this car, the rear seat was working just fine.
The driver’s seat had three problems.
The button which moved the seat rearwards didn’t work. However, the seat may be moved backwards with one of the memory keys.
The front of the seat couldn’t be raised.
Your head restraint wouldn’t move down or up, although in such a case the motor could be heard whirring uselessly whenever the right buttons were pressed.
Getting the Seat Out
The initial step ended up being to take away the seat from the car so that use of all of the bits could be gained. The seat was electrically moved forward and then the two rear floor-mounting bolts undone.
But exactly how was access going to be gained to the front mounting bolts? Pressing the adjustment button didn’t increase the risk for seat to maneuver backwards, and through this stage the memory button had stopped allowing that action as well! The answer was to manually apply power to the seat to activate the motor. All of the connecting plugs were undone and those plugs containing the heaviest cables inspected. (You will have wiring for seat position transducers and such things as that within the loom, nevertheless the motors will likely be powered by noticeably heavier cables.)
Using a durable, over-current protected, 12V power source (this one was created very cheaply – see DIY Budget 12-volt Bench Supply), power was applied to pairs of terminals connecting for the thick wires until the right connections were found. The seat was then powered backwards until the front mounting bolts could possibly be accessed. These were removed and so 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
And this is what the BMW seat seems like underneath. Four electric motors can be seen, plus there’s a fifth inside of the backrest. Each electric motor connects to a sheathed, flexible drive cable that therefore connects into a reduction gearbox. When I later discovered, inside each gearbox is actually a worm that drives a plastic gearwheel, which often drives a pinion operating over a rack. At this time, though, a simple test may be created from each motor by connecting ability to its wiring plug and ensuring the function worked since it should. Every function although the head restraint up/down worked, and so the problems besides your head restraint showed that they must stay in the switches, not the motors or associated drive systems. But exactly how to fix the top restraint up/down movement?
The rear trim panel of the seat came off with the simple undoing of four screws. Much like another seat motors, the mechanism consisted of a brush-type DC motor driving a versatile cable that traveled to the adjust mechanism. The motor worked fine with power connected, but the head restraint didn’t move. Feeling the beyond the drive cable sheath established that the drive cable inside was turning, and so the problem must lie within the mechanism closest to the head restraint itself.
The adjustment mechanism was locked in place with one screw, that was accessible together with the leather upholstery disengaged from small metal spikes that held it set up. The legs of the head restraint clipped into plastic cups in the mechanism (one is arrowed here) and they were able to be popped by helping cover their the careful consumption of a screwdriver.
The complete upper portion of the adjustment mechanism was then able to be lifted out from the seat back and placed next to the seat. Remember that the electrical motor stayed in place – it didn’t have to be removed as well.
To see what was going on within the unit, it needed to be pulled apart. It absolutely was obviously never built to be repairable, so the first disassembly step involved drilling out of the rivets which held the plastic sliders into position on their track. Using these out, the act of the pinion (a compact gear) in the rack (a toothed metal strip) may be assessed. Neither looked particularly worn and applying power to the motor demonstrated that the truth is the pinion wasn’t turning. To ensure meant that the issue was in the gearbox itself.
The gearbox was held combined with four screws, each by having an oddly-shaped internal socket head where I don’t have a tool. However, understanding that I could possibly always find replacement small bolts, I used a set of Vicegrips to undo them – that may be, it didn’t matter once they got somewhat mutilated at the same time of disassembly.
Inside the gearbox the worm drive as well as its associated plastic gear may be seen. Initially I assumed that the plastic cog will need to have stripped, but inspection revealed that this wasn’t the situation. Why then wasn’t drive getting away from the gearbox? Again I applied capability to the motor and watched what went down. A Few Things I found was even though the cable could possibly 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 demonstrated that the end in the cable was a little worn and yes it was slipping back from the drive hole of your 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 little, crimp a spring steel washer upon it (backed with a plain washer that here has run out of sight – it’s fallen into the mouth from the sheath) then push the drive cable down again in the sleeve. Together with the crimped washer preventing the worn section of the cable from sliding back from the square drive recess within the worm, drive was restored on the gearbox.
The mechanism could then be reassembled. New screws were used to switch the Vicegripped ones, as 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 placed on the tracks the nylon sleeves run using. During the seat, the mechanism dexqpky30 checked by utilizing power – and worked fine.
So in cases like this the fix cost nearly nothing, except some time.
Since all 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 the seat during the car – it looked just as if it must be a wiring loom or switchgear problem. But while the seat was out, it made sense to wipe over-all the tracks and exposed cogs and re-grease them.
Fixing the Rest
Within the driver’s seat can be a control Power seat switch both relays as well as the seat memory facility. Close inspection of your plugs and sockets on the machine and the associated loom indicated that some corrosion had occurred. (Perhaps at some stage a drink ended up being spilled upon it.) The corrosion showed itself like a green deposit on the pins and 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 from the deposit in the pins in the plug, that were otherwise impossible gain access to to clean.
At commercial rates, fixing the seat will have cost large sums of money – in labour time and in a complete replacement head restraint up/down mechanism. Nobody could have bothered repairing the gearbox drive – they’d have just replaced the whole thing. The corroded pins? That might have been cheaper, although the total bill might have still been prohibitive.