Power Seat Motor – Check Out Every One of the Options Whenever Looking at the Systems Included If Shopping For Power Seat Motors.

If you pick an older luxury car there are 2 things near certain: first is that this may have Power seat flexible shaft, and the second is that a minimum of one in the seat functions won’t work! So how hard will it be to correct a defective leccy seat? Obviously it all depends a great deal about what the exact dilemma is and also the car involved, but like a guide let’s look into fixing the seats within an E23 1985 BMW 735i. The seat architecture in other cars may vary, however if you don’t have idea where you’d even learn to fix this type of problem, this story is sure to be useful to you.

The top seats from the BMW are one of the most complex that you’ll find in any older car. They have got electric adjustment for front/back travel, front of 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 also don’t have airbags. (If the seats you are concentrating on have airbags, you have to look at the factory workshop manual to ascertain the safe procedure for working on the seats.)

The seat functions are common controlled by this complex switchgear, which is duplicated around the passenger side in the car. As can be seen here, the driver’s seat also offers three position memories. Incidentally, the rear seat is additionally electric, with an individual reclining function for every side! However in this car, the rear seat was working perfectly.

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 front from the seat couldn’t be raised.

The head restraint wouldn’t move up or down, although in this case the motor might be heard whirring uselessly whenever the best buttons were pressed.

Having the Seat Out

The initial step was to take away the seat from the car in order that usage of all of the bits could be gained. The seat was electrically moved forward and therefore the two rear floor-mounting bolts undone.

But exactly how was access gonna be gained for the front mounting bolts? Pressing the adjustment button didn’t result in the seat to advance backwards, and through this stage the memory button had stopped allowing that action at the same time! The answer was to manually apply capability to the seat to activate the motor. Each of the connecting plugs were undone and people plugs containing the heaviest cables inspected. (There will be wiring for seat position transducers and things like that inside the loom, nevertheless the motors is going to be powered by noticeably heavier cables.)

By using a durable, over-current protected, 12V power source (this was developed very cheaply – see DIY Budget 12-volt Bench Supply), power was used on pairs of terminals connecting towards the thick wires till the right connections were found. The seat was then powered backwards before the front mounting bolts could possibly be accessed. These were removed and then the Power seat motor moved forward until it sat in the middle of its tracks, making it easier to escape the auto.

Fixing your head 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 motor unit connects to your sheathed, flexible drive cable that subsequently connects to some reduction gearbox. As 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 made of each motor by connecting capacity to its wiring plug and ensuring the function worked because it should. Every function nevertheless the head restraint up/down worked, so the problems aside from the pinnacle restraint showed that they must maintain the switches, not the motors or associated drive systems. So how to repair the top restraint up/down movement?

The back trim panel from the seat came off by 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 traveled to the adjust mechanism. The motor worked fine with power connected, but the head restraint didn’t move. Feeling the away from the drive cable sheath indicated that the drive cable inside was turning, therefore the problem must lie in the mechanism nearest your head restraint itself.

The adjustment mechanism was locked in place with one screw, that has been accessible using the leather upholstery disengaged from small metal spikes that held it set up. The legs in the head restraint clipped into plastic cups on the mechanism (the initial one is arrowed here) which could actually be popped by helping cover their the careful use of a screwdriver.

The complete upper part of the adjustment mechanism was then able to be lifted out of the seat back and placed near the seat. Be aware that the electric motor stayed into position – it didn’t must be removed too.

To find out what was going on in the unit, it needed to be pulled apart. It had been obviously never built to be repairable, and so the first disassembly step involved drilling the rivets which held the plastic sliders into position on his or her track. Using these out, the action of the pinion (a little gear) about the rack (a toothed metal strip) may be assessed. Neither looked particularly worn and applying capability to the motor demonstrated that the truth is the pinion wasn’t turning. So that meant the situation was within the gearbox itself.

The gearbox was held combined with four screws, each by having an oddly-shaped internal socket head where I don’t possess a tool. However, knowing that I could possibly always find replacement small bolts, I used some Vicegrips to undo them – that is certainly, it didn’t matter when they got a little mutilated at the same time of disassembly.

Inside of the gearbox the worm drive along with its associated plastic gear might be seen. Initially I figured that this plastic cog will need to have stripped, but inspection indicated that this wasn’t the situation. Why then wasn’t drive getting away from the gearbox? Again I applied capacity to the motor and watched what actually transpired. A Few Things I found was while the cable might be heard rotating inside its sheath, that drive wasn’t arriving at the worm. Pulling the worm gear out and inspecting the square-section drive cable showed that the final of your cable had been a little worn plus it was slipping back out of your drive hole from 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 of the sheath just a little, crimp a spring steel washer into it (backed with 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 in its sleeve. With the crimped washer preventing the worn area of the cable from sliding back out from the square drive recess within the worm, drive was restored towards the gearbox.

The mechanism could then be reassembled. New screws were utilized to replace the Vicegripped ones, as the drilled-out rivets were also substituted for new screws and nuts (arrowed). The gearbox was re-greased before assembly and a smear of grease was positioned on the tracks that the nylon sleeves run on. In the seat, the mechanism dexqpky30 checked by applying power – and worked fine.

So in cases like this the fix cost nearly nothing, except some time.


Since every one of the motors had now been proved to be in working order, fixing the electrical rearwards travel and front up/down motion could basically be achieved using the seat during the car – it looked as though it would have to be a wiring loom or switchgear problem. But as the seat was out, it made sense to wipe overall 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 both the machine and the associated loom indicated that some corrosion had occurred. (Perhaps at some stage a drink have been spilled onto it.) The corrosion showed itself as a green deposit on the pins plus some tedious but careful scraping by using a small flat-bladed screwdriver removed it. Once which was done, the associated plug was inserted and pulled out 20-30 times to scrape from the deposit within the pins from the plug, that were otherwise impossible to gain access to to clean.

At commercial rates, fixing the seat might have cost hundreds of dollars – within labour efforts and within 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 could have been cheaper, although the total bill will have still been prohibitive.