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Old 10-04-2023, 09:55 AM   #1
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TS/Mk4/G Astra convertible roof latch motor fix

So the roof on the missus' Astra was cactus, it just beeped for ten seconds every time she switched the car on. After looking at this page, I was able to follow the instructions in reverse to crack it open and have a squiz at the gubbins... you can push the roof through its range of motion and the hydraulic fluid just blows past the pistons in the cylinders, which makes sense - if the pistons sealed fully like normal hydraulic cylinders, they'd be a hazard to people who get in the way, and to the mechanism in case of a malfunction.

Here's another page with some more info. What neither page tells you is that using the allen key manual override on the latch destroys the plastic gear inside. Usually the gear will already be stripped before anyone tries it, but it's kinda crucial info.

Getting the latch cover off is a bit tricky. If the plastic blocks on your latches are cracked so the manual override doesn't work, I reckon you'd be out of luck and have to cut it away to get at the latches. Otherwise, you have to open the latches all the way, which pops the front up a bit, and maybe even lift up the back too, which allows the front to keep coming up. Then have a look along the side of the roof for a couple of straps secured with little torx screws; there's one towards the back on the outside of the frame, and one towards the front on the inside. Removing those screws (don't drop the fiddly little bastards) allows you to get an arm in between the roof fabric and headlining. Poke a light source in there, and you can see nine philips screws, which holds the front of the headlining and the back of the latch cover to the roof frame. There's another four philips screws on the front of the cover.

I made sure the latches were closed but the beeping didn't go away, so I tested the hall sensors in the front of the roof and the top of the windscreen, and they were working okay... turned out the tonneau cover wasn't latching closed, because its cylinder hadn't fully retracted. Tied a bit of thin rope onto the end of the cylinder so I could pull it all the way home after the cover was closed, and that put a stop to the beeping. That was a win on its own.

Meanwhile, I went looking for a replacement for the sacrificial gear, thinking it should totally be a spare... all I could find initially was the corresponding part for the next model, as an aftermarket part in brass. Or the whole unit, for like $500 from the UK. Browsing down the UK page, I saw replacement latch parts, which were for TS Astra and E46 BMW - ahah!

So I repeated my search, substituting E46 for Astra, and Bob's yer uncle. In brass, just like all the wrong ones I found earlier. If you need to replace the plastic gear in the latch drive on your Astra, here's your search term:

I got mine for under twenty bucks, turned up in a week. It came with the other gear that lives inside the unit along with four plastic bushings, but I didn't use that stuff because the new bushings were tight AF, and the old ones were fine, and the gears weren't as good quality as the original brass one.

Put the drive unit back together, after lubing the gears with all the spare grease from inside the unit, and used a battery charger to break in the new gear - I just gave it some juice for a minute or so, until it stopped going faster, then reversed polarity and gave it another shot for a bit. Sweet. But now, the manual override is not a thing, despite the new part having a spot to stick your allen key - there's no way you can turn a gear that's engaged with a worm drive, not happening. I considered moving the connector on the motor power over to above the right door, to make overriding possible in future, but then I figured it wasn't worth the hassle since the brass gear isn't going to strip in a hurry.

I put the unit back in the roof, ready to see what else was wrong... when I was investigating the system, I saw the hoses were pretty tired, with the outer all crumbled off the weave on every hose where it experiences movement, and one of them was slightly pink from a minor weep that had left a bit of a film of oil around the right side of the roof mechanism down in the back. I'd rubbed off all the loose outer and just taped up the hoses with electrical tape for a bit of abrasion protection, with an extra layer or two of gaffer tape where they'd actually been rubbing (the tape isn't worth a damn as far as holding in the fluid goes). Anyway, I figured the weep was probably minimal enough to get away with since the fluid level was still good, but on the other hand I wouldn't have been surprised if it needed more troubleshooting.

Sure enough, the roof stopped opening just after the latches had opened and the front popped up a bit. I looked at where the latch mechanisms were in their travel, and they hadn't finished opening. Part of these mechanisms reaches back along the side of the roof to another latch, which pushes the roof a bit further open before the mysteries of the roof frame take over driven by the hydraulic cylinders at the back... Hmm. I gave it another try, this time taking a bit of the weight off the front with a little push, and away she went! Opened all the way, with the tonneau cover latched no worries. Closed all the way too. Hell yeah.

But the missus wasn't satisfied. "What do you mean it needs a push?" *sigh*

So I pulled out the latches (a 1/4” rattle gun helped a lot here, those bastard T35 screws were tight AF), and spent a couple of hours messing around to minimise the friction. As they open, the second part of the movement is where they got stuck and the motor stalled, where the side latches get actuated. I'd pulled the circlip out so I could punch out the drive shaft with its bearing, and then unscrewed it from the plastic block to see where most of the friction was coming from. Turns out it was the slot in the outer edge holding the rod running back along the side. Removing the screw there revealed a wavy washer, which I swapped out for a plastic washer; that made a good amount of difference without adding much slop to the joint.

The side latches which the rods attach to were also pretty stiff; pulling one of those off and giving it a lube and refitting it did stuff-all, so I had another look. Grabbed the orphan wavy washer and popped it over the screw, and the.OD was a perfect fit to add a little clearance for the pivot. The ID was a little large though, so a dab of grease held it in the right spot while I screwed the latch back on (just using the wavy washer as a flat spacer since it's crushed flat by fully tightening the screw).

Gave it another test, and bam! Sorted. I reckon I might have just boosted the resale value of these cars a bit with this info... have at it.

Last edited by Stealthee; 10-04-2023 at 05:49 PM.
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