Why do electric windows only work with ignition on?

[rcx106]

I'm doing some rewiring in my Vitara, to wire up the Hellas, diff lock compressor, and new alarm and some other little bits. While I'm at it I'm considering any other tweaks, and one annoyance is that the electric windows don't work if the ignition is not on.

So one guy told me this is to stop the battery draining. Maybe because the leccy windows use relays. Is this right?

Considering one of those modules that attaches to the car alarm and closes the windows when the alarm is switched on. How do these devices know that the window has closed? The Vitara does not have any sensor or intelligence in the windows at all. The motor pumps for as long as the user is pressing the button.

[andyiley]

I would have thought it was more to do with security.

Such that you couldnt open the windows when the car is locked, perhaps with a wire coat-hanger through the window, but I am only guessing.

Or to stop the opening of the windows after the ignition is switched off, but before the doors are locked.

[CrutyRammers]

Not all do - a lot of cars now let you operate the windows for a few minutes after turning the engine off. But yes, I imagine it's to stop people running the battery down by playing with the windows.
They will use relays, but that's nothing to do with why they won't work with the ignition off.

[Locknut]

It's also a safety feature. Several children were killed over the years while playing in cars and getting their heads caught in closing windows.

If you want to change it, it might be possible to take the supply from a permanent source instead of the present switched source.

[Faust66]

When I bought my car a previous owner had fitted an electric window conversion that was permanently wired in to a live feed. Some of the wiring was a bit sub standard so I completely renewed it a couple of years back – I followed the original trace of all the associated wiring. In 5 years of ownership I’ve never had a problem with the set up draining the battery.

I didn’t use a relay on the main live feed (there wasn’t one fitted and as windows are only operated for a couple of seconds I didn’t think it was necessary ) but installed separate inline fuses on each of the live feeds (one of each window) for added safety.

[steveo3002]

theives could poke a coat hanger in and open the window , faulty switch could open the window or maybe burn out the wiring if jammed on the up direction

[Jimmyarm]

steveo3002 said:

theives could poke a coat hanger in and open the window , faulty switch could open the window or maybe burn out the wiring if jammed on the up direction

It's much quicker to smash it with a brick

[dbfan]

Many years ago, some children were hurt when playing with "live" electric windows - One was almost strangled (if not killed) when they wound the window up while they had their head hanging out of the window. I seem to think it was "That's Life" (Esther Rantzen's show before Watchdog came along) that campaigned for them to be made so that they wouldn't work if the key was removed.