760 Sunroof Woes

[russwinchester]

I’m in the middle of recovering the headliner, so it was time to tackle the sunroof, it was opening fine but once open, would not return. Ive hooked it up to 12v on the battery and the motor (and roof) moves in both directions. I’ve checked the car and as much as the switch is a bit slack there is 12v supply to the motor assy. I’ve had the motor gearbox apart to check functionality and all looks ok physically. So I’m figuring it’s a micro switch problem. I’m just a bit concerned ripping the micro switch assembly to bits if I don’t need to; of course they are NLA and my only option is a used part from Lithuania at £150 with no guarantee of course.

Have I arrived at the right diagnosis?

Does anyone have a spare sunroof motor assembly squirrelled away to save me the hassle?

Thanks!

[360beast]

Open up the switch, the brass rocker switch burns on the ends so you need to clean them up. That's what I've been finding and the same with window switches.

[Laird Scooby]

What Luke said Russ! ^^^^^ It might show you have 12V coming out of the switch under no-load conditions but as soon as the motor is connected, that will drop considerably. It's almost always the switches that fail in the way Luke described, rare that the motors fail. I think i have a spare motor but would need to check.

Talking of the motor, you may find that it runs backwards and forwards on the switch if you unbolt it from the roof assembly. This again demonstrates the switch can only pass a certain amount of current. You will also notice that it automatically stops in the closed position when you send it in either direction from a fully open position - bear this in mind when refitting it as getting it one tooth out can result in the panel sitting proud or recessed in the roof.

If you don't fancy pulling the switch apart, with the ignition off, spray some switch/contact cleaner in the gap between the switch rocker and housing then "exercise" the switch in both directions several times. Repeat a couple of time, finishing with a good squirt just into the gap and leaving it for 20 minutes or so for the alcohol to evaporate before testing with the ignition on.

You have already proved the motor works though and the only microswitches are built in to the motor assembly.

[russwinchester]

Just whipped the switch out, things don’t look good in there 😩. It’s been apart before…one of the brass contacts is so flat that it looks like it’s permanently connecting, and the nylon roller bush (looks like a mini dumbbell) looks melted on one side, there’s a good flat melted part 😳. I’ll see if I can get some plastic filler and make good, of course the switches are NLA, like everything…

[Laird Scooby]

Originally Posted by russwinchester

Just whipped the switch out, things don’t look good in there 😩. It’s been apart before…one of the brass contacts is so flat that it looks like it’s permanently connecting, and the nylon roller bush (looks like a mini dumbbell) looks melted on one side, there’s a good flat melted part 😳. I’ll see if I can get some plastic filler and make good, of course the switches are NLA, like everything…

If you talk nicely to Luke i think he may have a 760 style sunroof switch Russ, failing that i believe i have.

It sounds as if the switch has stuck in one position or the other (not centrally) and someone has driven around for a month of sundays like it.

I doubt you can recreate the plastic roller, Milliput would be my choice to try though.

[Pete940]

Also check the "worm" part of the mechanism. Not sure if it has a technical name but I've had one where the worm had loads of deteriorated headlining material stuck to it.
I hate sunroofs. I'm replacing a saloon headlining right now so I know your pain.
If you come to a dead end then maybe you could look for a manual winder mech instead.

[Laird Scooby]

Originally Posted by Pete940

Also check the "worm" part of the mechanism. Not sure if it has a technical name but I've had one where the worm had loads of deteriorated headlining material stuck to it.
I hate sunroofs. I'm replacing a saloon headlining right now so I know your pain.
If you come to a dead end then maybe you could look for a manual winder mech instead.

That's a very valid point about the "worm" (technical name - worm, it's a worm and pinon or worm and gear drive system) but he's already proved it's the switch and stripped the switch and found the evidence.

There were no manual winder versions of the 760 sunroof and i'm fairly sure the 740 used a slightly different mechanism so although some of those had manual winders, i'm fairly sure they're not interchangeable.

[Whippy]

On the roller, see if you can find some shrink tube to fit over. You may need to do some profile restoration first but the tube will give it a proper surface.

[tofufi]

Originally Posted by Laird Scooby

That's a very valid point about the "worm" (technical name - worm, it's a worm and pinon or worm and gear drive system) but he's already proved it's the switch and stripped the switch and found the evidence.

There were no manual winder versions of the 760 sunroof and i'm fairly sure the 740 used a slightly different mechanism so although some of those had manual winders, i'm fairly sure they're not interchangeable.

I converted my 1990 740 to electric sunroof using the components from a 1989/90 760.

The motor was a direct fit/swap for the manual winder.

The gear didn't have a worm, it had a normal spur (or possibly helical spur, I don't remember) gear.

[Laird Scooby]

Originally Posted by tofufi

I converted my 1990 740 to electric sunroof using the components from a 1989/90 760.

The motor was a direct fit/swap for the manual winder.

The gear didn't have a worm, it had a normal spur (or possibly helical spur, I don't remember) gear.

The worm is in the sunroof frame Jim. The gear/pinion on the motor provides the drive to the worm. Interesting that you were able to use 760 bits to pgrade your 740 though.