Sunroof Troubleshooting

[nickbartleet]

I'm just finishing up the restoration of my 944, and I have a problem with the sunroof that I feel like I am close to diagnosing but can't quite work it out.

Up and down works with ignition on perfectly now after some fettling. The problem comes when i go to release the roof latches. Instead of it sliding back until limit switch 2 has depressed and stopping, the dog slides past limit switch 2 until the roof latches bottom out. This of course means that limit switch 1 is working, but limit switch 2 is not, however I have checked both limit switches and even switched them around and the problem persists. I have checked and again switched around both of the relays too and no difference. Each time, it ignores limit switch two and retracts all the way back untill it bottoms out and the dog go's past limit switch 1 and limit switch 1 breaks contact.

I have checked the wires coming from limit switch 2 to the console switch and they are reading OL and CL as they should.

Could this problem be the console switch. I don't seem o be getting the same readings as the clarks garage troubleshooting pages suggest I should. Terminals 1 and 3 seem to be reading 93 ohms not less than 1 ohm when in the rear position and a few other anomalies, but i'm confused that the switch seems to be working when the ignition is on for the up and down.

It would be great to get thoughts from anyone who is more familiar with this than i am before buying anything new.

[dme]

I know relay 1 and two are adjusted together, but could it be possible that relay two is physically not getting engaged? Relay would be good, but arm just not pushed down far enough.

[nickbartleet]

Well that makes a lot of sense, but i'm testing the relay by manually rolling the dog over it and off it, so no i don't think so.

[nickbartleet]

Fixed it. Read the clarks garage article in detail and realised that for the latches to retract they should move into close closed on the two limit switches but must also bottom out sooner on the car bodywork which they were not doing, so that the dog doesn’t overshoot the limit switches and is stopped by the motor slip clutch instead when the latches hit the roof opening.

What i did is put a hard stop (plastic piece bolted onto the end of the rail where i wanted the dog to stop with the latches fully open... well before the dog over runs the limit switches sending them to open open, and confusing the whole system.

Everything works perfectly now.

[nickbartleet]

This put too much force on the rail so and caused it to snap. Had to fix the rail and then took gearbox apart again and found the snakes had worn down causing them to slip on the gear which is why the dog was overshooting in the rail. I managed to carefully remove the latch snakes from the gold tubes, remove the crimps holding the snake to the latch, trim and inch off and reassemble, putting the crimps back on and all is working like its fresh out the factory.

If you have worn or slipping snakes/ gears in an early car it is a fairly easy job with a good vice, a hacksaw and some old drill bits.

[rbuswell]

I'm also using Clark's Garage repair guide. My car is a '87 924S so it has the new sunroof design. Both plastic gears were bad which I replaced with the brass URO gears. A very nice upgrade BTW and reasonably priced. I think I have everything indexed correctly after I figured out that Clark's diagram for the mounting plate and cam is actually a mirror image of the actual set up (Grrr). When I move the cable manually, I can hear the #2 micro-switch engage (clicking noise). If I put my hand under the mounting plate and press on the #3 micro-switch I can hear it click too. Not when I move the cam manually to that end though. I can't hear #1 at all.

When I started testing everything under power I did it with the sunroof out. The arms would move to the roof locked position but not to either of the other positions. With the roof in and the front micro-switch engaged, the arms would move to all three positions but wouldn't stop at any of them including the #2 locked. When I get to either end of the motion the clutch is working but the switches don't stop anything. Just the whirring noise of the motor. Of course I let up on the center console switch immediately to prevent damage.

My questions are:

1. Any idea why the #2 switch would work with the sunroof out but not when it's in?
2. Can there be another reason why the micro-switches wouldn't work other than they are bad? ... e.g. some other adjustment I'm not seeing or that was not included in Clark's manual.
3. The PET shows that switch #1 & #2 are the same part number but it doesn't even show switch #3 at all. Anyone have any idea what the part no. is or how to find it? The PET is usually the best resource.

[dbonds007]

Originally Posted by rbuswell

I'm also using Clark's Garage repair guide. My car is a '87 924S so it has the new sunroof design. Both plastic gears were bad which I replaced with the brass URO gears. A very nice upgrade BTW and reasonably priced.

[...]

Question/thought on the "brass replacement gears" - in the event of anything going wrong with limit sensors (which you already indicate are sketchy in your setup) or other portions of the sunroof system, the "most fragile part" will likely break first. I'd rather loose a few teeth off a plastic/nylon gear than burn out motor, snap cable, or break something else in the mechanism.

Thoughts/concerns with using brass gears instead of plastic?

[rbuswell]

Originally Posted by dbonds007

Question/thought on the "brass replacement gears" - in the event of anything going wrong with limit sensors (which you already indicate are sketchy in your setup) or other portions of the sunroof system, the "most fragile part" will likely break first. I'd rather loose a few teeth off a plastic/nylon gear than burn out motor, snap cable, or break something else in the mechanism.

Thoughts/concerns with using brass gears instead of plastic?

Although Clark didn't come right out and say it, he implied that the reason the gears get stripped is the clutch isn't set correctly. I have backed way off on the tension from where the prior owner had it set. Clark recommended a torque of 6 Nm which is practically nothing. I suspect most owners set the tension way too high.

I can't really say why Porsche used such an under-built gear but it is really a crappy part. My theory is that Porsche builds race cars for the street and they only offer features like sunroofs, electric mirrors and door locks, etc. because buyers who aren't really enthusiasts demand the luxuries. Since Porsche doesn't want to include them, they don't focus on doing a good job. If I had my way, the cars wouldn't have any of that stuff but since my car has it, I want it to work.

[911tracker85]

we just replaced the lift mechanism, one was broken, and the sunroof motor, existing one too weak.

we replaced the broken lift and cleaned up those parts, but motor still would not move them.

got a used motor, installed it, and it works fine now. but the console wiring is a bit of a mess from the PO and no sunroof switch.

we are suspecting the PO took stuff apart trying to troubleshoot what was an bad motor. it runs but will not move the lift mechanisms. got all the parts, relays, and wiring with the replacement motor (Thanks Plyhammer!). so will source a switch and see if we can get it to work normally. but when necessary I tend to go the 'creative wiring' approach. a few years ago I wired up a toggle switch for my trolling motor direction control, and may do the same with this. bypass all the intermediate microswitch, etc. we'll see....

[UROParts]

Originally Posted by rbuswell

My car is a '87 924S so it has the new sunroof design. Both plastic gears were bad which I replaced with the brass URO gears. A very nice upgrade BTW and reasonably priced.

Thanks for the feedback! These gears are pretty tiny considering their function.

If anyone else is interested, Pelican offers brass Sunroof Drive Gear 944 564 430 01-PRM at a great price.

[911tracker85]

considering the wiring mess decided to just go creative...

got a two way switch, and jumpered the outputs by crossing the wires. worked perfect. need to tidy up the wiring today. them move on to the next job.

[rbuswell]

... at least I don't think it's perfect.

I installed the new micro-switches, adjusted it per Clark's instructions and all the functions work well now. The only thing I don't think is correct is the arms that raise the roof only raise it about 1 1/2 inches. They will extend much higher manually but they stop raising like you would expect them to based on a switch working. Is 1 1/2 inches all it should go up?

[911tracker85]

we had to 'reset' those arms to their highest position manually. that is, open up the gear box and manually raise them to the correct height, and then ensure the motor is at it's highest point, then reassemble the gearbox. work perfect now.

but then I dropped the sunroof and broke both of the rear brackets into which the arms fit. getting another sunroof from Plyhammer.

but we have the car out and running. some sputtering/surging at high rpm, hoping a new set of plug wires, cap, rotor, and coil fix that.

[rbuswell]

Originally Posted by 911tracker85

we had to 'reset' those arms to their highest position manually. that is, open up the gear box and manually raise them to the correct height, and then ensure the motor is at it's highest point, then reassemble the gearbox. work perfect now.

but then I dropped the sunroof and broke both of the rear brackets into which the arms fit. getting another sunroof from Plyhammer.

but we have the car out and running. some sputtering/surging at high rpm, hoping a new set of plug wires, cap, rotor, and coil fix that.

So after you were done, the unlock, lock and raising the roof all the way all worked correctly? One hates to disparage the dead but I only wish Clark had included that step in his instructions. His directions for unlocking the roof for removal with the later sunroof didn't include the all-important need to turn the key off before using the unlock function at the control switch either. If it was there, I missed it. It wasn't until I read the owner's manual that I got that part. It is a safety measure I assume so you have to turn the car off before removing the sunroof. Sorry to hear about your busted roof. That sucker is really heavy so I understand how it could happen.

I'll have to decide if I want to go through the brain damage again for an inch or so of additional lift. It is an inordinately difficult process especially when you count messing with the headliner and rear deck lid seal. I'm wondering how you make sure the motor is in the right spot for the fully open spot since you can't see inside it. I had tried a similar idea by setting the cam to the right spot manually while matched with the arm fully engaged before I put it back together which didn't work. Thanks for the insight.

BTW, I have a pretty lively thread going on for my 924S about driveablity problems that focuses on the AFM and fuel pressure. If the parts you are planning to replace are old, they are a good start. But if they are fairly new, give some thought to the AFM and fuel pressure and fuel regulator.

[911tracker85]

well it worked until I dropped the panel...

and since I bypassed all the original wiring and little micro switch it just raises and lowers based on pushing the rocker switch.

not sure if you can get the roof off if the arms are not all the way up.

currently I think the cutting out issue is electrical. first time I thought may be fuel. but after a couple more test drives pretty sure it is elec. think I saw that thread but once I moved toward thinking elec, attack that first.

[rbuswell]

Originally Posted by 911tracker85

well it worked until I dropped the panel...

and since I bypassed all the original wiring and little micro switch it just raises and lowers based on pushing the rocker switch.

not sure if you can get the roof off if the arms are not all the way up.

currently I think the cutting out issue is electrical. first time I thought may be fuel. but after a couple more test drives pretty sure it is elec. think I saw that thread but once I moved toward thinking elec, attack that first.

The micro-switches are a nice touch but they also limit the movement of the arms and motor so as not to stress out the plastic gear wheels. I switched to the URO brass wheels but I turned the clutch way down to reduce the chance of trashing stuff. Caught a little flak for using brass and doing it that way, fearing I would mangle the drive cable. The clutch can be set way down and still drive the system. That and the working micro-switches was my compromise.


BTW, I think you want to make sure the arms are fully retracted before you take off or put on the sunroof.

[rolls 912]

On of my 968, the sunroof lifting arm (RHS) is not working. I can manually lift it. The other side operates perfectly.

I assume the sacrificial plastic gear has topped itself. Would that be right?

What’s the verdict on the brass gear? I would have thought Porsche would have deliberately allowed the plastic one to fail in place of more expensive components in the system?

[rbuswell]

The theory is that Porsche used a plastic gear so that a malfunction or wrong adjustment wouldn't ruin the long toothed cable. It probably is a risk but it seems worth it to not have to take apart everything to replace the cheap plastic gear. So far the brass gear seems to be a good solution but I'm still sorting out adjustment. That isn't the fault of the gear though.

If you replace one plastic gear, I would replace them both with brass. You'll have it all apart anyway. Unfortunately, you have to mess around with the headliner, the hatchback seal and a bunch of other stuff to get this job done. It is an example of why Porsche is a racing car company. They aren't very interested it making jobs like this easy to do. I've never worked on a Porsche that's post-Toyota consultation in the late '90s but I suspect that newer cars don't have this sort of under-engineering on creature comforts.

[UROParts]

Normally automakers choose plastic to cut weight (to help maximize MPG) while reducing material and manufacturing costs, but that's just an assumption. Modern transmission pans, intake manifolds, and cooling system components are now plastic instead of metal, but are in no way fuses in the system.

[rbuswell]

Originally Posted by UROParts

Normally automakers choose plastic to cut weight (to help maximize MPG) while reducing material and manufacturing costs, but that's just an assumption. Modern transmission pans, intake manifolds, and cooling system components are now plastic instead of metal, but are in no way fuses in the system.

I'm pretty sure you guys made my brass gears. Well made part.

Ferdinand Piech would have fully endorsed your premise that he was saving weight with plastic over brass. By then, he was at either Audi or Volkswagen IMS when the 924s were being built ... after he created the firestorm that caused the Porsche family to be ousted from management. They had to settle for eventually being billionaires. Tough duty. Piech was a brilliant engineer but a stubborn, PITA to work with. Drilling holes in the ignition key, seriously?!

The difference in weight between your brass gears and plastic were negligible. Porsche was known for overbuilding some items that added unnecessary weight. If our cars were built like a Lotus, they'd be light like a feather but wouldn't make it out of the driveway.