If you pick an older luxury car the two main things near certain: the first is that it could have Power seat motor, and the second is the fact at least one of your seat functions won’t work! Now how hard will it be to solve a defective leccy seat? Obviously it all depends a good deal on which the specific concern is and the car under consideration, but as being a guide let’s take a look at fixing the seats inside an E23 1985 BMW 735i. The seat architecture in other cars can vary, however, if you don’t have any idea where you’d even learn to fix such a problem, this story is sure to 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 got 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 plus they don’t have airbags. (In the event the seats that you are working on have airbags, you must read the factory workshop manual to find out the safe procedure for taking care of the seats.)
The seat functions are common controlled by this complex switchgear, which can be duplicated about the passenger side of your car. As can be seen here, the driver’s seat also has three position memories. Incidentally, the back seat is additionally electric, having an individual reclining function for each and 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 might be moved backwards using one of the memory keys.
The top 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 proper buttons were pressed.
Receiving the Seat Out
The first task was to remove the seat from the car so that entry to every one of the bits may be gained. The seat was electrically moved forward and therefore the two rear floor-mounting bolts undone.
But just how was access gonna be gained on the front mounting bolts? Pressing the adjustment button didn’t make the seat to go backwards, and also by this stage the memory button had stopped allowing that action too! The answer was 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 see wiring for seat position transducers and things such as that within the loom, however the motors is going to be powered by noticeably heavier cables.)
Using a high quality, over-current protected, 12V power source (this particular one is made very cheaply – see DIY Budget 12-volt Bench Supply), power was used on pairs of terminals connecting on the thick wires before the right connections were found. The seat was then powered backwards before the front mounting bolts could be accessed. They were removed and therefore the Power seat switch moved forward until it sat during its tracks, making it simpler to get free from the vehicle.
Fixing the pinnacle Restraint
This is what the BMW seat appears to be underneath. Four electric motors is seen, plus there’s a fifth in the backrest. Each electric motor connects to a sheathed, flexible drive cable that consequently connects into a reduction gearbox. While I later discovered, inside each gearbox is actually a worm that drives a plastic gearwheel, which drives a pinion operating on the rack. During this period, though, a straightforward test may be created from each motor by connecting capacity to its wiring plug and being sure that the function worked since it should. Every function nevertheless the head restraint up/down worked, and so the problems besides the pinnacle restraint showed that they have to maintain the switches, not the motors or associated drive systems. But exactly how to repair the head restraint up/down movement?
The back trim panel of your seat came off through the simple undoing of four screws. As with one other seat motors, the mechanism was made up of a brush-type DC motor driving a flexible type of cable that traveled to the adjust mechanism. The motor worked fine with power connected, nevertheless 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 inside the mechanism closest to your head restraint itself.
The adjustment mechanism was located in place with one screw, that has been accessible using the leather upholstery disengaged from small metal spikes that held it in place. The legs in the head restraint clipped into plastic cups about the mechanism (the initial one is arrowed here) and these could actually be popped out with the careful utilization of a screwdriver.
The whole upper section of the adjustment mechanism was then able to be lifted from the seat back and placed near the seat. Keep in mind that the electric motor stayed in position – it didn’t should be removed as well.
To see that which was occurring 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 in place on their own track. By using these out, the act of the pinion (a tiny gear) on the rack (a toothed metal strip) may be assessed. Neither looked particularly worn and applying capability to the motor demonstrated that in fact the pinion wasn’t turning. In order that resulted in the problem was within the gearbox itself.
The gearbox was held as well as 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 may be, 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 might be seen. Initially I figured how the plastic cog must have stripped, but inspection revealed that this wasn’t the case. Why then wasn’t drive getting out of the gearbox? Again I applied capacity to the motor and watched what actually transpired. Things I found was while the cable might be heard rotating inside its sheath, that drive wasn’t progressing to the worm. Pulling the worm gear out and inspecting the square-section drive cable indicated that the end of your cable was a little worn and it was slipping back out from the drive hole from the worm. (The slippage was occurring inside the area marked from the arrow.)
The fix was dead-easy – simply pull the drive cable out of the sheath a little bit, crimp a spring steel washer on it (backed from a plain washer that here is out of sight – it’s fallen into the mouth from the sheath) and after that push the drive cable back down in its sleeve. With the crimped washer preventing the worn area of the cable from sliding back out of your square drive recess within the worm, drive was restored to the gearbox.
The mechanism could then be reassembled. New screws were used to replace the Vicegripped ones, while 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 put on the tracks how the nylon sleeves are powered by. In the seat, the mechanism dexqpky30 checked by utilizing power – and worked fine.
So in such a case the fix cost nearly nothing, except a little while.
Since all of the motors had now been proved 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 like it had to 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 can be a control Power seat switch both relays as well as the seat memory facility. Close inspection of your plugs and sockets on both the device as well as the associated loom demonstrated that some corrosion had occurred. (Perhaps at some stage a drink have been spilled onto it.) The corrosion showed itself as being a green deposit around the pins and a few tedious but careful scraping with a small flat-bladed screwdriver removed it. Once which was done, the associated plug was inserted and pulled out 20-30 times to scrape off of the deposit in the pins of the plug, which were otherwise impossible to gain access to to wash.
At commercial rates, fixing the seat would have cost a lot of money – in both labour some time and in a complete replacement head restraint up/down mechanism. No one might 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.