If you opt for an older luxury car there are 2 things near certain: the first is it can have Power seat motor, and also the second is the fact one or more from the seat functions won’t work! So, just how hard would it be to fix a defective leccy seat? Obviously it all depends a good deal on what the actual concern is as well as the car involved, but like a guide let’s take a look at fixing the seats in a E23 1985 BMW 735i. The seat architecture in other cars can vary, but when you don’t have idea where you’d even commence to fix such a problem, this story will certainly be appropriate to you personally.
The front seats inside the BMW are amongst the most complex that you’ll find in any older car. They already have electric adjustment for front/back travel, front of 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. (In the event the seats that you will be taking care of have airbags, you need to look at the factory workshop manual to find out the safe procedure for working on the seats.)
The seat functions are controlled from this complex switchgear, which happens to be duplicated about the passenger side from the car. As is seen here, the driver’s seat also offers three position memories. Incidentally, the rear seat can also be electric, by having an individual reclining function for every side! But in this car, your 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 possibly be moved backwards using one of the memory keys.
The front from the seat couldn’t be raised.
The pinnacle restraint wouldn’t move up or down, although in this instance the motor may be heard whirring uselessly whenever the right buttons were pressed.
Receiving the Seat Out
The first step ended up being to get rid of the seat through the car in order that usage of every one of the bits could be gained. The seat was electrically moved forward and then the two rear floor-mounting bolts undone.
But just how was access going to be gained for 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 answer was 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. (You will have wiring for seat position transducers and such things as that in the loom, but the motors is going to be powered by noticeably heavier cables.)
Utilizing a durable, over-current protected, 12V power source (that one was created very cheaply – see DIY Budget 12-volt Bench Supply), power was applied to pairs of terminals connecting on the thick wires till the right connections were found. The seat was then powered backwards till the front mounting bolts may be accessed. These were removed and so the Power seat motor moved forward until it sat during its tracks, making it easier to get out of the auto.
Fixing your head Restraint
This is exactly what the BMW seat seems like underneath. Four electric motors is visible, plus there’s a fifth inside the backrest. Each motor unit connects into a sheathed, flexible drive cable that therefore connects to your reduction gearbox. As I later discovered, inside each gearbox is actually a worm that drives a plastic gearwheel, which drives a pinion operating on a rack. During this period, though, a basic test may be manufactured from each motor by connecting capacity to its wiring plug and ensuring that the function worked as it should. Every function although the head restraint up/down worked, therefore the problems besides the top restraint showed that they have to 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 of your seat came off from the simple undoing of four screws. Just like the other seat motors, the mechanism consisted of a brush-type DC motor driving an adaptable cable that went along to the adjust mechanism. The motor worked fine with power connected, although the head restraint didn’t move. Feeling the outside the drive cable sheath indicated that the drive cable inside was turning, hence the problem must lie from the mechanism nearest the head restraint itself.
The adjustment mechanism was kept in place with one screw, that was accessible together with the leather upholstery disengaged from small metal spikes that held it in position. The legs of the head restraint clipped into plastic cups on the mechanism (the first is arrowed here) and they could actually be popped out with the careful use of a screwdriver.
The entire upper part of the adjustment mechanism was then able to be lifted out of the seat back and placed next to the seat. Note that the electrical motor stayed into position – it didn’t have to be removed at the same time.
To discover that which was taking place 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 your rivets which held the plastic sliders into position on his or her track. With one of these out, the act of the pinion (a small 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. To ensure resulted in the issue was inside of the gearbox itself.
The gearbox was held together with four screws, each with the oddly-shaped internal socket head in which I don’t possess a tool. However, understanding that I really could always find replacement small bolts, I used a couple of Vicegrips to undo them – that is certainly, it didn’t matter if they got somewhat mutilated in the process of disassembly.
Inside of the gearbox the worm drive as well as its associated plastic gear could be seen. Initially I figured that this plastic cog will need to have stripped, but inspection demonstrated that this wasn’t the truth. So just why wasn’t drive getting out of the gearbox? Again I applied ability to the motor and watched what went down. Things I found was even though the cable might 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 showed that the end in the cable was a little worn plus it was slipping back out of the drive hole in the worm. (The slippage was occurring in the area marked with the arrow.)
The fix was dead-easy – simply pull the drive cable out of your sheath a bit, crimp a spring steel washer onto it (backed from a plain washer that here has run out of sight – it’s fallen into the mouth of your sheath) then push the drive cable down again in their sleeve. With the crimped washer preventing the worn area of the cable from sliding back out of your 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, 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 that the nylon sleeves run on. Back in the seat, the mechanism dexqpky30 checked by using power – and worked fine.
So in this instance the fix cost nearly nothing, except a bit of time.
Since every one of the motors had now been became in working order, fixing the electric rearwards travel and front up/down motion could simply be achieved together with the seat in the car – it looked as if it would have 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 remainder
Under the driver’s seat is really a control Power seat switch both relays as well as the seat memory facility. Close inspection from the plugs and sockets for both the device and the associated loom indicated that some corrosion had occurred. (Perhaps at some stage a drink have been spilled upon it.) The corrosion showed itself as a green deposit around the pins and several tedious but careful scraping by 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 the pins from the plug, that were otherwise impossible gain access to to clean.
At commercial rates, fixing the seat might have cost hundreds of dollars – within labour some time and within 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 might have been cheaper, although the total bill would have still been prohibitive.