1995 993 sunroof question

tteplitzmd · 09-17-2008, 04:37 PM

Which part(s) are defective if the sunroof opens, closes, properly, motor works just fine, but motor no longer seems to shut off when the sunroof is finished closing?

It is as if the motor is continuing to try to close the sunroof after it has fully closed--and now makes a clicking/gear turning kinda noise.

BeauBlues · BeauBlues's Garage

I would first assume that there is a short in the switch. Maybe it's not fully releasing when you want it to.

jimmcc · 09-17-2008, 06:34 PM

I agree with BeauBlues. Looking at the wiring diagram there is nothing trick about the setup, just a switch and motor.

The sound you are hearing is the sunroof transmission. It may have a slip clutch that would make that noise. If not, it is the sound of plastic gears doing bad things to each other. I would locate the fuse and pull it until the console switch can be checked and or replaced.

Jim

1995 993

tteplitzmd · 09-18-2008, 03:36 AM

But the console switch, itself, correctly powers on and off---it is as if the motor continues to try to close the sunroof, causing the gears to keep going---my recollection is that the motor would continue before, but the gears would disengage when working correctly (at least that's my theory). Am I wrong?

jimmcc · 09-18-2008, 05:39 AM

You are correct. The switch powers the motor in either direction and the transmission has a slip clutch to disengage the motor from the transmission when the end limit is reached on the roof movement either way. There are no limit switches to interrupt the power to the motor.

I believe you are experiencing two problems, (1) the console switch is bad and is not interrupting the current flow when you remove you finger and (2) the slip clutch or the gears or grinding on the transmission probably due to being over worked due to problem number 1.

I checked my 95 sunroof this morning to confirm the previous observations. When I have the sunroof at either limit and bump the switch I can hear the motor start and a slight bump as the clutch engages and then begins to slip.

Start by replacing the switch and hope that you do not have to replace the transmission as it will be expensive.

Hope this helps

Jim

1995 993
1980 930

tteplitzmd · 09-18-2008, 06:33 AM

Thank you jmmcc. I think you've got it!

tteplitzmd · 09-18-2008, 06:45 AM

Actually, re-reading your comment, let me clarify, the motor powers off correctly when I let go of the switch---so doesn't tha suggest it's in the clutch?

jimmcc · 09-18-2008, 12:05 PM

If the motor is off then there is nothing to drive the clutch or transmission so now I'm a bit confused as to the nature of the problem. As I indicated earlier, there are no limit switches and the motor is driven forward or backward directly from the console switch.

Jim

tteplitzmd · 09-18-2008, 03:22 PM

Jim, doesn't it have to be the slip clutch?

The rocker switch on the console, when pushing to retract, can be pushed down, and does not engage the motor after the sunroof is fully retracted.

Now, when the rocker switch is pushed to close the sunroof, the motor remains engaged as long as the rocker switch is depressed (and you get the grinding rat a tat tat until you release the rocker switch). That is, you've got release the switch to stop the motor now. It wasn't like that before.

It would seem to me that the rocker switch is correctly functioning, it effectively only powers the motor on and off, and that's working in both directions.

Does that seem correct? If it is the slip clutch, is that the dreaded $100+ rubber clutch, with a lot of labor vs. the $50 actuating swtich?

Terry

jimmcc · 09-18-2008, 04:15 PM

Terry,

I'm understanding your problem a bit better now. I spent some time looking at PET. Porsche is using the same motor, slip clutch and transmission as the SC. The cables are different.

I have not worked on a 964/993 but I have rebuilt a couple of SC chassis and am familiar with that arrangement. Based on your last post I am now thinking it may be the pull cables. I don't believe it is the slip clutch as I would think if it were bad you would have the same problem at full retraction and close. What I am thinking, based on SC experience, is that at lest one of the pull cables is partially striped at one end and therefore the transmission never develops enough tension for the slip clutch to sense. The rat-a-tat-tat sound is the transmission gear grinding on the end of the cable. That would explain why you hear it in one direction but not the other. The motor itself is very quiet and you may not have noticed it running in the past. I don't believe it has a time out timer built in to limit the run but am not sure.

The real problem is that if it is one of the cables, eventually it will strip and the sunroof will close slightly cocked and then will jam (open of course). Most of the sunroof problems I have dealt with were of this nature and they always were the result of at least one worn cable.

Replacing them is not easy from a time and neck strain consideration. If I remember correctly you have to lift the sunroof up and out after disconnecting it which is very tight and a study as to prevent an scratch.

The slip clutch is a rubber sleeve between the motor shaft and the transmission shaft and the more I think about your problem the less I believe it is either the switch or the slip clutch. Is the sunroof closing all the way and popping up to seal the roof as it should? Sometime if the cable has problems it will not complete the close process.

Hope this helps

Jim

1995 993 with rarely used sunroof due to cabin buffeting
1980 930 with sunroof switch disabled as the cables are bad

tteplitzmd · 09-18-2008, 04:32 PM

Well, Jim, you must be psychic!

The roof is not closing completely now, without a few seconds more of pushing the console button, but it is closing completely, and will stay that way until such time as I can brave the next step.

I think you're right about the slip clutch, I thought the same thing: it disengages in one direction, not the other. The console switch is doing it's job in both directions.

I am afraid to even open it again, but if I did have it fully retracted, can you visualize which cable is bad from inspecting the cable/guides? Elsewhere on this site is a nice article about removing the sunroof/cables. It sounds like a lot of work, with a lot to go wrong with the headliner and sunroof assembly. Bad news right?

jimmcc · 09-18-2008, 05:40 PM

Terry,

I believe it is called "been there - done that". It just took a bit to revive the memory cells.

You can actually push the sunroof forward a bit as you close it with the switch and that will often give enough additional force to close it and seal the op. Otherwise it will be prone to leaking and being noisy but that beats being open.

Other than dismantling the sunroof I know of no way to examine the cables as they run in tracks along the sides of the sunroof. Replace both of them and don't worry about which one is bad. If you don't, you will get to do it all over on the old side.

Post a link to the article. I'll read it and try to remember the fun of doing it. You have to be careful at two stages, removing and sliding back the headliner cover to prevent it from being cut and removing the sunroof panel without scratching it or the roof. Having someone to help you remove the panel is an asset as well as putting it back in. Like I said earlier, I don't have any experience in doing it beyond the SC but remember a lot of little screws and pieces. Other than worrying about hurting the paint it's not that difficult just a neck pain working in the close space above your head.

Jim

tteplitzmd · 09-19-2008, 04:09 AM

http://www.pelicanparts.com/techarticles/911_sunroof_repair/911_sunroof_repair.htm

Thanks Jim. The article is pretty comprehensive, and recommends replacing all the seals. My 911 has been garaged, the sunroof rarely used, and I am inclined to skip those replacements. Would I need any parts beyond the two cables?

More important, does anyone know of anybody in the Washington, DC, area likely to be competent to do this???