Electric Window - Limit Switches?

[Paddy_SP]

I'm in the middle of installing electric windows to the front doors of my '93 110 which are being built up from bare - before putting the glass in place I thought it'd make sense to power the systems up to check that all works properly. While the mechanisms go up and down as expected, I was surprised to find that when they are at their travel limits the motors still draw lots of power. I would have thought that there would be limit switches to shut them off at this point - both sides do the same thing, and both are brand new, so I very much doubt there's a component problem. Am I just expecting too much design sophistication or am I missing something?

[Bowie69]

Expectations way above what it needed I'm afraid -not come across any vehicle that uses limit switches in their windows, though I don't tend to work on anything VERY modern, so who knows how they have managed to complicate things in recent years!

[Paddy_SP]

Ah - thanks for that - my background is in motor racing (especially motor cycles), so windows are a bit of a new concept to me!

Edited December 22, 2021 by Paddy_SP

[Retroanaconda]

I don’t think even cars that have one-touch window switches use a limit switch, given everything is computer controlled now they probably just monitor the current draw on the motor to know when they’re either closed or trapped on something.

In ‘good old fashioned’ motors like a Defender the limit device is the person taking their finger off the button once it’s fully open/shut 

[ThreePointFive]

The only car I know of that does is an XK8 (and by extension any car that has frameless windows) because they need to know where they should sit when up, without a physical barrier.

I'm glad the answer was 'not needed', none in mine and I'm very happy with how they work.

[Paddy_SP]

Thanks for your continued comments! I've replaced (well, repaired) the regulators in my D1 several times over the years, but I've never bothered to look very deeply into the electrics. When one of the rears stopped working, I just disconnected it as I didn't use it. 

[Mo Murphy]

3 hours ago, Retroanaconda said:

I don’t think even cars that have one-touch window switches use a limit switch, given everything is computer controlled now they probably just monitor the current draw on the motor to know when they’re either closed or trapped on something.

In ‘good old fashioned’ motors like a Defender the limit device is the person taking their finger off the button once it’s fully open/shut 

Or the winder won't turn anymore 😁

Mo

[David Sparkes]

Having owned a 1995 LR model that had electric windows, from LR ....

What you are fitting now is certainly illegal now, and was probably illegal then, if  installed by the manufacturer.

They have to allow that children might be involved, either in pressing the button, or in lacking the self preservation instincts they will hopefully go on to develop.
Nowadays the control system has to recognise if the window stops 'early', and reverse the movement for a second or so, so that the 'screamer' can remove their fingers from the trap.

As a private individual you can of course carry on as you are.

Regards.

[Paddy_SP]

Many thanks for the info - my rusty old brain must have heard something along these lines for the thought process to have been triggered!