Driver's Side Window Really Slow to Go Down (1978 SC)
 

Problem: The driver’s side power window on my 1978 SC (US spec) is extremely slow to go down for the first two thirds of its travel, and has only gotten slower over the last few months. It is much better when going back up, but is still fairly slow on the final third as it closes. It’s at its worst when it’s raining/wet.

Symptoms:

1. (see video) the leading (front of car) edge of the window doesn’t seem to sit in the guide properly at first, and “sticks” until I give it a gentle push on the trailing side: https://www.dropbox.com/scl/fi/h144pkvgcz9st2ppmqrfk/Video-Jan-15-2024-12-39-31.mov?rlkey=2fy053ckr9bvy41pxh8ztad3h&dl=0
2. (see video) …which also causes (or vice-versa) the window regulator mechanism to flex and push inwards on the door itself with quite a bit of force. I’ve re-torqued those bolts, but ultimately there is very little adjustment with these earlier type parallel-arm regulators: https://www.dropbox.com/scl/fi/txf4a6gphltlcodamriml/Video-Jan-16-2024-12-45-05.mov?rlkey=c9se1p07ha4jrn8x6j2eacubc&dl=0
3. (see video) The rear of the window lags behind a little, which is likely related to #1: https://www.dropbox.com/scl/fi/vchjue9pfy1jr20cmf9h3/Video-Jan-16-2024-12-45-22.mov?rlkey=3mepj2gtfreyo5dixpk64rlfo&dl=0

It feels like the entire window is misaligned throughout its travel down, however it does close/seal against the top of the frame (no leaks, no meaningful wind noise) at the end of its travel.


What I’ve checked:

* The felt guides look good: great, even! The felt is smooth and in-tact all the way down on both leading and trailing edges.
* The stand-offs that secure the regulator to the door panel don't seem to have any play: when the regulator flexes against the door, the entire regulator flexes. The stand-off have no wiggle/play, as I've seen from others with regulator issues.
* The horizontal guides/rails that the window slides across inside the door look OK: no rust or debris, and I don’t see the window sticking or jolting inside the clamps
* I’ve also adjusted the bottom bracket/clamp that holds the window frame and thus the leading window guide rail in an attempt to better align (camber) it with the leading edge of the window. A very minor difference here, at best, but I don’t think I’ve exhausted the adjustment here.
* I think the motor is OK, because the window is almost normal at the bottom third of its travel on the way down, and “decent” on the way back up as described before. The teeth seem to mesh OK with the regulator.
* I replaced both the felt seal and the outer rubber seal a couple of months ago, as the inner felt seal was in pretty bad condition. No difference.


Notes

I have read a LOT of threads on this, and many of them talk about regulator adjustment, but...

* The early year (78-79) SC’s do not have the later scissor style regulator, but instead the earlier-model parallel-arm regulator, and thus don’t have the same adjustment screws later (1980+) - e.g. https://forums.pelicanparts.com/porsche-911-technical-forum/1046451-window-parallelism-adjustment.html
* There’s a tech bulletin on replacing the regulator (which means drilling new holes in the door panel) - https://members.rennlist.com/emcon5/Tech_bulletin_7.pdf - but I am as-of-yet unconvinced the regulator is the issue, and want to be sure before I embark upon that fun journey (and buying a $600+ regulator from our host).
* Passenger side window is totally fine.

Disassembled door panel (note the lack of adjustment due to the older regulator):

http://forums.pelicanparts.com/uploa...1705433805.jpg

Obligatory photo of the car:

http://forums.pelicanparts.com/uploa...1705433924.jpg

Since you haven't had any bites, I'll share some thoughts. I don't have much experience with Porsche windows, but have some experience with other cars.

It seems like the window is experiencing a lot of drag in the channels. The window goes faster at the bottom because less of the glass is in the channel, hence less friction. Doesn't mean the regulator isn't failing though.

Troubleshooting ideas (non-exhaustive):

1. Lubrication. Lube the channels if possible. Silicone grease (not spray) has worked well on rubber channels (clean before applying the grease), but probably not good for felt. Lube the regulator where possible
2. Check the voltage supply to the regulator and work your way back to the switch if needed.
3. You could try removing the outer horizontal rubber seal at the top of the door panel to lessen the pressure on the window in the channel to check if drag is the issue
4. Adjust the window frame like was mentioned in one of your linked posts
5. Remove/support the glass and see how the regulator moves without it

Thanks!

This thread (https://forums.pelicanparts.com/porsche-911-technical-forum/1046451-window-parallelism-adjustment.html#post11644030) on window frame camber - also gave me a theory to run with.

My next steps:

1. Remove the window frame and see if the window moves smoothly up & down (which would confirm the window frame alignment theory)
2. Else, tape the window to the top of the frame and then pull the regulator out through the door and inspect it + the motor

The frame is much easier to remove vs the regulator, hence the ordering. There’s also a 13mm bolt at the back of the parallel arm regulator that I’m going to take a peek at too.

Does the cold affect motor speed ?

No. No better/worse on the driver’s side, and it’s been 25-35F here in NYC over the last week unfortunately!

Interested as my 1979 has the same issue on passenger side and last drive a few weeks ago the driver side started doing it as well. It is parked now for winter and I was going to dig into next weekend.

Let me know what you uncover. I’m about to tackle the frame & pull the regulator tomorrow and will update with any findings / photos.

Before you remove anything spray some lube in the window tracks to help diagnose it. If the operation improves, you know where to go. If there's no change, then do the voltage checks at the motor wires and check the regulator.

My SC was doing that. Both sides slow to some degree or another. I sprayed Wurth HHS 2000 (WD 40 would be OK) on the gear in there. The old grease had got a bit hard. Worked well after that.

Then at a later date I sprayed some white lithium grease on the gear for good lubrication.

and silicon spay on the felt channel.

Lube (3M ceramic, magic stuff) was the first thing I tried many moons ago, unfortunately. Both on the guides, on the tracks, and in the motor.

I can see the window misaligns in the track, which pushes on the regulator. Why it’s misaligned is still the mystery.

The 13mm bolt on the back of the parallel arm regulator was fine/tight, but re-torqued it for good measure.

Very cold out today so going to pull the frame this week when it warms up a bit.

Probably needs new felt. Easy to do without pulling the frame. The felt wears off and the glass drags on the base rubber. Lubing the felt with anything wet just makes things worse unless you used a dry teflon spray.

The felt — from the 90% I can see with the frame in the door, and the rest by touch — is in excellent condition. No obvious wear, sits neatly in the channel.

The lower 50% is just a guess. That's where the felt usually rubs off.

OK, after a ton of work travel, I’m back to trying to figure this out.

New theory: the window glass is possibly too far back in the horizontal guide, causing it to catch/drag?

- With the window frame removed the window works fine - perfect, even. That’s a huge win!
- The felt guides are fine - no issues at all - on both sides.
- The frame is very hard to put back in on the rear: its hard to see but it’s as if it catches on the edge of the clamp/guide that holds the glass on the back side?

That may be why it “pops” out of position on the front edge until I push the rear down to re-align it.

http://forums.pelicanparts.com/uploa...1707567636.jpg

I forgot to update this, but earlier this year:

* On a rally in Florida (put the 911 on the Autotrain!) the window popped off the regulator wheels
* The next day it fell into the door and shattered
* I ended up taking it to a local shop once back in NYC and we rebuilt the regulator + new glass. Window worked and was fine.
* The shop claimed the screws at the top of the door - the ones towards the rear of the car that hold the frame in - were interfering with the window in the channel. This was odd (they were never changed) but given that the screws are 16mm (bottom) and 12mm (top) in length, and easily mixed up, it sounded plausible enough.

Fast forward to about 3 weeks ago and… we’re back to square one. The window is jamming again.

* About 1/5th of the way down the window seemingly “catches” at the rear, tilting it in the frame so it’s kinked about 5-6 degrees forward. With some force I can push the rear down and get the window to move, but it’s not great. It will NOT make progress on its own.
* Felt channels are fine - great, actually. No obvious issues - as far as I can tell with the window still in the door/frame in the door.
* Door card off so I could run a plastic trim tool up & down to check for obstructions.
* The window goes UP fine, slightly slowing when it hits this “trouble point” but only a little.
* I have checked all fasteners (nothing was loose) and adjusted the pitch of the frame & bottom of the rail to only minimal effect.

This is pretty infuriating: I’m open to ideas here or recommendations for a good shop in NY/NJ/CT that can take a look.