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944 rear hatch locking mechanism


DC242

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I've just undertaken the tail light upgrade as mentioned in another forum with great results. Very easy and looks great. Anyway, why I was under the carpet thought I'd investigate how the rear hatch lock works.

I don't know if what I have is standard or something is missing. Presently, if you turn the key to open the hatch or use the button inside, the motor continues to function until you let off. There's no spring/s to "pop" the hatch away from the catch, so you have to guess when the lock has released the hatch pins, which can be very frustrating when your seated and wanting to open the hatch. Then, once you've lifted the hatch, you have to again use the key or the switch to bring the lock "jaws" back together again so you can close/lock the hatch.

If this is standard, its a piece of crap engineering. If this is not correct and something is missing from my system, I'd like to establish what I'm missing and set about fixing this annoyance. Any pictures appreciated.

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When I first got the car I had the same issue because I was pressing the hatch release for too long. I would go out and it isn’t unlocked so have to back and press it again. Usually if I press it just the once it is okay.

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Your gas struts should exert sufficient pressure to release and raise the hatch when they are in good condition.  As time passes, they lose pressure and require a helping hand to release.  You'll find the problem is worse in cold weather than in hot.

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Oh my goodness DC242 ,   "pierce of crap engineering" , could you imagine if this was the case when these cars were new ??????? , of course it wasn't, and you know that as well , think about it and may be you can figure out what is not correct 30 years later ( yes 30 years later ) 

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All i need to do is push the button once, it'll do 1 cycle, and i can lift the hatch. And for 30 years old, the system is fine. If the hatch is coming apart from the frame, it pushed the hatch back causing the pins to lock more which makes unlocking it harder. 

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Sorry about the "crap engineering" quote but I had a 40 year old Volvo that had an electric boot release from new. If this is the way Porsche designed the system from new, barring a little loss of pressure in the gas struts, then I know what I have to work with.

Pauly, you say that pushing the button once and it'll do one cycle. I'm guessing this means the locking jaws open, releasing the hatch pins and returning to the lock position? Mine doesn't release the pins so I have to guess the time for a half cycle, lift the hatch then press the button again for a half cycle to get it ready to lock.

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My 86 works fine, but there a list of things that you can check.

The latch jaws, are they working correctly, there is a hatch pin seat in each latch. Over time they perish and fall apart these pieces can stop the jaws from working correctly.

https://www.only944.com/partscatalog/only/hatchpinseats/

The latch's may not be located correctly, if they are out a little your hatch will not pop up. 10mm ring spanner and a lite touch.  The info below has how to adjust.

https://www.only944.com/instructions/hpsinstructions/

Then there is of course you gas struts, but if you can use your key and the hatch opens and hatch stays up, my guess is your struts are fine. 

Information

A noisy rear hatch (squeaking or rattling) can be caused by several different things.

Over time, the hatch seals tend to dry out and shrink. As a result, the hatch does not fit as tightly and it can rattle or squeak. If so, this can often be corrected by adjusting the two posts on the rear hatch. To adjust the posts, loosen the lock nut next to the hatch. To tighten the post, turn it clockwise several turns and then tighten down the lock nut. Be careful not to tighten the post to much or the hatch will difficult to latch and unlatch.

Another possible cause is latch mechanism for the rear hatch. The latch mechanism needs to periodically lubricated. Use a good quality grease to lubricate the latch mechanisms on both sides. A combination of lubrication and adjusting the posts will often solve a squeaky hatch.

Finally, the most difficult hatch repair is caused by the rear glass separating from the hatch frame. This is caused by repeatedly slamming the rear hatch. The vibration caused by slamming the hatch closed, over time, causes the glass to separate from the frame. That's why it's important to close the hatch by lowering it down against the hatch opening gently and then pushing down on the rear of the hatch to latch it.

There are several schools of thought with regard to repairing the rear hatch. Many will tell you that the car must be taken to a professional glass service to be re-glued. While this does ensure a quality repair, it can also be very costly. There are others who have taken on this repair themselves and have successfully repaired the rear hatch. However, the hatch has to be removed from the car for repair. So, if you decide to do the repair yourself, you should have someone assist you during the removal and installation.

Repairing Separated Glass

Introduction

There are a number of different sealants/adhesives that can be used to repair the rear hatch glass. The best ones are urethane based. Probably the best overall is 3M Window Weld Urethane Auto Glass Sealant.

I've added a few notes to the procedure that follows which were devoloped by Russ Bullock and provided by one of our members. The notes added are intented to help with separateing the rear hatch glass from the trim and the frame.

Procedure

 

  1. Remove the rear hatch as follows:

     

    1. Disconnect the rear window defroster wires (one on each side).
    2. This step is not mentioned in the factory shop manual. If you have a rear wiper, the power and control wires for the wiper must be disconnected from the wiring harness. This connection is not anywhere near where the wires feed into the rear body pillar. It is accessable thru the side panel. Then these wires must be withdrawn thru the hole in the rear pillar near the top of the hatch. I nearly yanked them out in a bad sort of way when I first tried to remove the hatch. (Russ Bullock)
    3. Disconnect the rear hatch shocks.
    4. Lower the rear hatch but do not allow it to latch. You may place a piece of wood between the back of the hatch and the body to prevent the hatch from latching.
    5. From inside the car, remove the bolts that hold the rear hatch hinges to the body of the car (2 hinges - 2 bolts per hinge). On early cars, there's a cover over the hinges. On later cars, the rear header panel will have to be removed.
    6. Have someone assist you to lift the rear hatch off of the car.

     

  2. Remove the trim strips from around the edge of the hatch. You'll find clips that hold the strips in place. In most cases, the clips are accessed from the underside of the hatch.

     

    Note from Russ Bullock

    Removing the spoiler trim is a royal PITA! The top trim was a snap. The side trim is attached with what I would call knurled-knob nuts which have nearly useless flat-blade slots in the top of them. The factory must use a special tool to fit over the stud and engage these slots on each side of the nut. I used brute force (i.e., a pair of vise-grips). The rear spoiler is attached with phillips head machine screws with a hardness rating similar to that of warm butter. I actually got a couple of them off with a screw driver, but most had to be drilled out.

     

  3. Work slowly and carefully to pry the frame off of the hatch glass. Scrapers usually work well for separating the glass from the frame.

     

    Note from Russ Bullock

    The sealing compound had completely let go from the glass at the left hinge, which was the motivating factor behind this project, but the remainder of the seal was still very much intact. Separating the glass from the frame is the toughest part of the job. I started with a 1.5" wide flexible putty knife to slip between the glass and the seal. The metal blade and the amazing rubber-kryptonite sealant did not want to slip past each other without considerable force and a variety of four-letter words. WD-40 applied to the working surfaces helped greatly. I also sharpened the end of the blade by grinding on only one side (like scissors) and used the unground side on the glass side of the bond. In addition to this putty knife operation, draw your attention to the top side of the hatch and use a good sharp utility knife to cut the outer edge of the glass from the sealant. WD-40 comes in handy here too. Cutting this edge bond first allows the putty knife operation on the other side of the glass to go a little more smoothly. I kept a thin block of wood wedged between the glass and frame where I had already achieved separation. This helped to force open the gap so that the putty knife could do its job. Take care with the wedge block so that the frame is flexed, but not bent. Overall, it took me four hours to separate the glass from the frame.

     

  4. Using an adhesive remover and scraper, remove the remains of the old sealant.

     

    Note from Russ Bullock

    Once separated, I cleaned the glass of remaining sealant with a razor blade scraper followed by 4X steel wool. I tried using a Scrub-Brite pad, but found that it left slight scratches in the glass surface. I used some fine polishing compound and a cotton cloth to remove scratches that might be seen after the glass is re-bonded. I might actually grind or sand a rough surface into the glass at the bonding surfaces near the hinges to make a stronger bond there. Any thoughts or warnings about this idea would be most appreciated.

    Concerning the use of solvents to soften the sealant: GOOD LUCK! I even went so far as to try GumOut carb cleaner, the stuff with Xylene and other possibly carcinogenic (and definitely flamable) solvents. That sealant took everything I could throw at it, then threatened to taunt me a second time. Apparently the only thing that can make this stuff turn loose is 20 years of UV solar radiation.

     

  5. Reinstall the hatch frame onto the car with it in the closed position. Do not attach the hatch shocks yet.
  6. Make sure the hatch frame fits properly to the hatch seals. Over time the hatch frame may have become bent and may need to be bent to get a proper seal.
  7. Place a bead of sealant all the way around the hatch frame following the directions for the adhesive.
  8. Place the glass on to the frame and push down around the edges to make sure the glass makes good contact with the frame. Here's a good suggestion from Vaughn Scott for installing the glass. "With the glass upside down, maneuver it so that it's behind the car with the rear edge facing forward. Place the rear edge of the glass in the rear of the frame and rotate it forward until the front of the glass is about a foot from being in place. Have one person hold it in place while the other person goes inside the car and takes the weight of the glass. Then the person outside of the car pulls their hands out of the way and the glass is lowered into place."
  9. Using the adhesive, fill in any gaps between the glass and the frame.
  10. Allow the adhesive to cure for at least 24 hours.
  11. Reinstall the trim strips and clips. This may require unbolting the hatch hinges.
  12. Attach the shocks to the hatch.

Clark's Garage © 1998

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The hatch on my S2 operates with either one quick press of the button or a single key turn now that I've done a few things.

First I replaced the hatch seals & the hatch pin seats with new seals & the above listed seat kit from only944. 

During this process I adjusted the location of the jaws so that they were in the right spot & at the right depth.  Later Rob helped me adjust the hatch pins to ensure they were at the right height. 

All up it was a few hours work (someone with more experience/ confidence that weren't going to fuck something up/ better tools would've completed it quicker).

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Port 911: thanks for the information and instructions.

Yesterday I removed and cleaned the locking mechanism's and discovered the hatch pin seals have perished and gone. This explains the annoying rattle. New ones ordered from 'only944'. The mechanism's themselves work fine and the motor is quick and quiet.

I've checked all the seals and they appear in good nick and the glass and frame appear happily united. The struts are doing their job at present but the test will be when the weather gets cold. I've also established that for one full cycle of the latch jaws takes one second. Hopefully when everything is put back together, greased and aligned the hatch will pop just enough to release itself and my judgement of one second will be accurate so as to have the jaws ready for the locking action. 

Learning this car little by little.

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  • 2 months later...

Has anyone here ever had the hatch glass separate from the frame? Those shocks required to lift the very heavy hatch put a lot of pressure on the seal.
As a precaution I disconnected the shocks,  but it is a PITA lifting the hatch with one hand to chuck stuff in.
But perhaps worth it rather than having to reseal the glass?

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40 minutes ago, tazzieman said:

Has anyone here ever had the hatch glass separate from the frame? Those shocks required to lift the very heavy hatch put a lot of pressure on the seal.
As a precaution I disconnected the shocks,  but it is a PITA lifting the hatch with one hand to chuck stuff in.
But perhaps worth it rather than having to reseal the glass?

I have had people talk about this, but have never known anyone that it has happened too. 

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5 minutes ago, Port 911 said:

I have had people talk about this, but have never known anyone that it has happened too. 

I guess it's possible some hatches have been pushed hard against suitcases or boxes, stressing the glass? Not every Porsche owner treats

the car with elderly  respect.

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2 hours ago, tazzieman said:

Has anyone here ever had the hatch glass separate from the frame? 

Yep this happened on my '86 and from what i researched it's all about keeping the hinges in good working order so they don't become stiff and put extra strain on the frame around the glass.

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If you try to close any 944 / 944S /951/ 944S2 /968  rear hatch that its gas struts that hold the strut up properly , meaning they have correct pressure & then you you attempt to close the rear hatch with (say) one hand and only one side of the rear hatch ( not in the middle )as a lot of people do  , just look at the amazing amount of flex / distortion the hatch glass & thin alloy frame has to deal with up and all along the top section of the hatch glass to thin alloy frame area , this is the reason they eventually separate , its all very basic human laziness in not knowing the consequences of closing one of these are hatches on one side only

Ideally the closure  of the rear hatch is with both hands ( one each side)  and close the hatch evenly

Its all very basic stuff when you see the flex when its not closed correctly  

Regards
Bruce Buchanan

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16 hours ago, brian in buddina said:

Bruce @Buchanan Automotive

Do you know what the correct pressure is for the struts? I would assume any strut would de-gas with the age of these cars. Is this something where you can get the original struts re-gassed?

Brian 

New struts are pretty cheap, well that's the route I took!

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The " new "gas pressure of the genuine made in Germany by Stabilus ( the real thing ) 944 rear hatch struts is meant to be 320N each ,  re gassing of the old rear lid gas struts is 98% of the time a waste of time & money , remember when the gas is gone ( after say X number of years & thousands of openings & closings ) the strut seal/s and its internal support bush/bearing will have minute amount of wear & you just can not successfully keep the "re-gassed " old  struts gassed to the correct pressure for more than a few weeks or months ( sometimes days ) , so the time & money spent is a waste of time & over the years / decades we have seen plenty of these old struts that had been "Re-gassed" previously just seize up , but most commonly they become very noisy when operated , remember inside these struts and other gas struts from the front lid or on other Porsche's , they have a very tiny amount of oil in them as well & its this oil that leaks out as they are loosing gas in the first place ( from wear & tear)

We have been through this( re-gas) years ago and in the end we had a 98% failure rate in getting Stabilus Porsche gas struts Re-Gassed , by 98% failure rate , I mean do they last like new ones after one year = NO  , most didn't even last months or weeks

So for years & years now we only purchase & install genuine made in Germany ( not Mexico ) Stabilus gas struts for Porsche cars we work on , it works out far cheaper in the long run

Regards
Bruce Buchanan
Buchanan Automotive

 

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  • 3 weeks later...

Well time flies and I'm still looking for the answer to my hatch opening issue. 

Since putting the hatch seals in and enjoying driving the car I've again been looking for the answer to how the hatch lock works. On mine when you press the button or turn the lock the latch motor stops immediately and the lock stays where it is, could be open/closed/half way between. Whilst scouring the interwebs this morning, I found this comment:-  

"Listen to the motor. It should run a bit and then when you release the button, you should hear the motor run momentarily once again. if you don't hear that, there's a white wire that plugs into the motor that has probably come out. That was my problem. I couldn't understand why sometimes I could close it and sometimes I couldn't. The motor is supposed to open and then return to the close position. This is operated through the white wire."

So, a quick look at my wiring revealed no white wire but it got me wondering what controls the motor and its self 'return'. Is it the switch, the lock or something in the motor? Does anyone know or point me in a direction to investigate further.

Additionally, where's the best place to purchase the Stabilus gas struts as with a quick change of weather the struts are showing their true condition.

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@DC242

The micro switch in the tailgate lock has a 'normally closed' contact (i.e. it opens when you turn the key) that keeps the motor running when you release the key or button.  If that contact has failed (or the wire detached/broken) the motor will stop as soon as you release the key (or button), rather than complete its rotation until stopped by the limit switch in the motor.  On my car the 'normally open' contact appears to have failed so I can only release the tailgate with the internal button.  If anyone has any experience with replacing the micro switch any tips would be welcome!!

Hope that helps

Tim

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On 3/29/2018 at 2:46 PM, Buchanan Automotive said:

The " new "gas pressure of the genuine made in Germany by Stabilus ( the real thing ) 944 rear hatch struts is meant to be 320N each ,  re gassing of the old rear lid gas struts is 98% of the time a waste of time & money , remember when the gas is gone ( after say X number of years & thousands of openings & closings ) the strut seal/s and its internal support bush/bearing will have minute amount of wear & you just can not successfully keep the "re-gassed " old  struts gassed to the correct pressure for more than a few weeks or months ( sometimes days ) , so the time & money spent is a waste of time & over the years / decades we have seen plenty of these old struts that had been "Re-gassed" previously just seize up , but most commonly they become very noisy when operated , remember inside these struts and other gas struts from the front lid or on other Porsche's , they have a very tiny amount of oil in them as well & its this oil that leaks out as they are loosing gas in the first place ( from wear & tear)

We have been through this( re-gas) years ago and in the end we had a 98% failure rate in getting Stabilus Porsche gas struts Re-Gassed , by 98% failure rate , I mean do they last like new ones after one year = NO  , most didn't even last months or weeks

So for years & years now we only purchase & install genuine made in Germany ( not Mexico ) Stabilus gas struts for Porsche cars we work on , it works out far cheaper in the long run

Regards
Bruce Buchanan
Buchanan Automotive

 

I bought a set of aftermarket struts from a firm in Victoria via ebay.  It was an entirely shite process.  First they were too soft - sent back.  Them they were too hard - sent them back for a refund - months of wrangling - finally full refund.  I just reinstalled my old Stabilus Struts & they are great.  If I was to do it again I would do as Bruce advises & buy the Ridgey Dige stuff from the Fatherland.

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