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Discussion Starter · #1 ·
Dear All

As I have mentioned in another thread, I'm hoping to be able to fix the front electric height adjuster on my driver's side seat (RHD car).

I spent a few hours (yeah, I'm a really rubbish amateur, should have been a few minutes work I'm sure...) taking the seat part way out and even got to the unit which is misbehaving, but now I'm a bit stuck.

Access is not great (I really hated trying to release the electrical connectors..) and it was only possible to get the relevant motor out by removing the screws that secure the front of the seat base to the lower frame and tilting it up a bit.

The motor spins when the buttons are pressed, however I think there must be a problem with one of the drive gears for it not to translate to any movement of the seat.

I removed the motor and the initial worm gear in the drive train and they look fine. Unless its something crazy like that squared off end to the flexible shaft for the worm gear not reaching far enough in to engage with the motor? It can't be that though, surely. I'm not hearing any teeth jumping nor do I see broken plastic / metal in the opening that the worm gear sits in.

Has anyone had a similar problem? I am well and truly stumped - plus all my fingers are sore from pulling those ghastly electrical connectors...:-(

I've loaded a few pictures which show where I got to.

Thanks in advance for any pointers!

tim

127930

(brown plastic bearing on the wrong way round for this next pic - sorry...)
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I have no personal experience with that are but looking at you pics and here is my line of thoughts (feel free fix my assumption):
1.the motor is working (True)
2. the squared end of worm gear (right side on the image) goes inside the motor (or motor housing) - true
Test this put the worm gear inside the motor housing and activate the motor. or just rotate the worm with your hand. - I'm trying to establish the fact that the end of gear that inside the motor is not broken/stripped and torque is passed from motor to the worm gear. agree? so if these rotate freely - mean you can rotate the gear and not feel you are turning the motor rotor (to turn the motor on and hold the gear and it wont rotate ... ) that means that what ever suppose physucally connect the motor shaft and worm gear is broken.

But actually you might skip this part because if you were able to pull out the worm gear from the aluminum housing without any effort it means than there is no connection between the gear and the toothed wheel that would be part of gearbox. in this case I would look into the aluminum housing...

Does it make sense?
 

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Discussion Starter · #3 ·
Many thanks for the reply. I have now put it all back together as I need to drive the car tomorrow...

However, I think I could probably get it back apart again fairly easily to check those kind suggestions :)

When I was 'in there' earlier, it was really not obvious how to remove the aluminium casting / gearbox.

Part of the problem is the very poor access, as I am reluctant to detach the seat belt anchor point from the seat unless I absolutely have to!

Does anyone have any experience of how these units on the P2 cars typically fail?

I was tempted to try and locate a second hand unit in the UK to better understand how it works. But alas I cannot even find the part number - even if it is possible to remove it from the frame.

kind regards, tim
 

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"....Ghastly...."
Best word ever. Some of these things will entirely drive an amateur crazy. Ask me how I know...
 

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You can get a used seat base and swap it over.
 

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Discussion Starter · #6 ·
Hi Exocet - yes indeed. That's pretty much what I plan to do. However, I'm going to initially attempt to swap out just the defunct gearbox unit. I've sourced an old seat base and have been stripping the parts off it in the kitchen (sorry to my Mrs...)
 

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Discussion Starter · #7 ·
The worst bit is removing that tension spring. I can hardly move it by hand, so I need to find a better way. Unfortunately, it really has to be removed to be able to get everything apart enough to remove a gear-box unit.

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It's not very obvious from this picture, but the two units are not identical - Volvo (in their wisdom) threaded the leading mounting hole of the front unit and the rear hole of the back unit. As these units are mirrored on the left side, that means four different gearbox casings. Crazy!
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On the other side is a cover plate which can be easily removed (everything thus far just needs Torx bits). Beneath this is the main drive shaft with a nylon transfer gear from the worm driven by the motor, which turns another metal worm which acts on the metal segment gears on the seat frame. Worst case would simply be removing this shaft and swapping for one from any of the four units as at this point my guess is they are most likely to be identical.
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Thus far, I'm impressed by the basic quality of the seat parts.

Next stage is waiting for a dry day to actually do the swap.

kind regards to all,
 

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Discussion Starter · #8 ·
Dear All:

I have finally gotten round to removing the faulty unit and replacing it with a good condition used one.

It turned out to be (for me at least) quite a tricky repair as I had to learn how to actually remove the faulty gearbox - I had not been able to find any tear down instructions for the P2 platform electric seats on either YouTube, Volvo forums or indeed on VIDA. That doesn't mean they aren't out there, it's just that I couldn't find them! Most of the lessons I learnt were from pulling apart a seat base from a scrap yard (sourced via eBay).

As I don't have a bench to work on I decided to try the fix without actually removing the seat from the car. For many of you this might sound daft, but I wondered if it was possible and it turns out that it is. There's also one quite good reason to have the seat in the car for one crucial step of the process and its reverse.

The first step was removing the rear seat base behind the driver’s seat – this allows the seat to be pushed or tilted back to a greater degree than with it still in place. There are no sharp edges either, so the back of my seat was going to be safe from potential damage.

Then you remove the four trim pieces covering the M14 bolts which hold the seat in place and then the those bolts as well.

Also, it helps to unclip the plastic unit holding the seat motor buttons, but I’m not sure now that was strictly necessary.

Then, the seat can be tilted back to give access for unplugging the main cable blocks you can see on the front of seat. This time I knew what I was doing and none of them gave any trouble.

At some point you also want to remove the two bolts that attach the front of the seat to the base. This means you can tilt the seat itself away from the seat base a bit and get much better access to the various bolts.

Next you release the plastic clip round the front motor which serves to keep the plastic ‘tray’ above it in place.

Then the motor is removed via two Torx 25 screws. This plastic tray then flaps down and you can release its outer clips to get even better access to the various bolts within the base of the seat.

Then, the worst part: removing the tension spring. This provides some assistance to the motor in overcoming the weight of the occupant and is incredibly strong; in fact I found it impossible to stretch without some mechanical advantage. In my case it was all made even worse by the fact that the seat was stuck in the lowest position, which is when the spring is tensioned to its greatest degree.

So I fashioned a simple tool from Meccano / Erector which can be seen in the image below. This is where it actually helps to have the seat rail bolted down (finger tight is more than enough) which gives you something to push against. Hence, having the seat actually in the car helped this step. The tool is simply a steel bar which pivots on a bracket resting in a convenient cup formed by the end of the gearbox casting. This in turn pulls on a narrow perforated strip of steel which has its end hole round the end of the spring. I provided the tool with a range of attachment points for this strip to suit the different requirements of removing the tension in the fully extended spring, vs the much easier process of returning the spring to its rightful place (carried out with the seat motor unit reassembled in its uppermost position such that I needed very little force).

After releasing the spring I also removed the seat frame bolts again.

With the tension spring unhooked, you can now actually remove the pivot bolts for the front raising mechanism. There’s the obvious black torx bolt which serves as the pivot for the toothed segment (driven by the motor) and its much shorter partner on the opposite side of the frame. The toothed segment is also retained in the gearbox by a metal pin – which is also simple to remove.

Then, you can finally undo the two screws which hold the gearbox in place and it literally drops out…

It had to cut two cable ties where I didn’t want to put to much strain on a couple of cables, but other than that nothing was destructive and it was all easily reversible – including putting the tension spring back in place once the replacement gearbox was fitted.

Sorry for the long post, I just hope it is helpful to someone else in the future. There aren't many pictures as I focussed on what for me was by far the most difficult step - releasing that spring!

I’ll cover what was broken in the gearbox in the next post!

tim

It wasn't necessary to have the seat frame bolted down to put the spring in place as the tension / force needed was so much less:
(sorry, no picture of the spring being released)
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My first attempt at this lever resulted in quite a few bent bits of Meccano. So I rebuilt it and packed it out with loads more strips and angle girders down its length to ensure it was strong enough for the task:
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there really is enough room to work on this without taking the seat out of the car. Ok, one or two bolts were a little awkward to get a straight line onto, but not that bad:
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I decided to re-use the old motor as it was working fine. I tested it of course before installation:
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Discussion Starter · #9 ·
I opened up the old gearbox to find what was wrong. The plastic drive gear (which mates with the worm on the end of the squared shaft which is spun by the motor) had cracked and fragmented so was never going to work again.

Thus far, I haven't dared drive the seat to its end stops in case it needs calibrating first. I'd really appreciate some advice on this aspect though.

The motors are equipped with two further terminals so I'm guessing they have a role to play in deciding when to kill power at the ends of travel.

Maybe it failed because the motor didn't stop when it was supposed to, some time back in the past?

any ideas? thanks in advance :)

tim
130357
 

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Impressive. Great set of details and text! Impressed also with the meccano lever thing you built!
 
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