Electric window motor

They're usually well and truly sealed because of the hostile environment. But I'd say it's unlikely the brushes would wear out anyway, given their limited use.

You're certain it's the motor and not the control or wiring to it? The switches, relays, and connectors are IMHO more likely to give trouble.

The only certain way is to apply battery volts direct to it. They're usually a simple two wire device with no ground required. Reversing the connections reverses the motor. If it's working but sluggish I'd first check for voltage drop.

Dave Plowman (News) ( snipped-for-privacy@davenoise.co.uk) gurgled happily, sounding much like they were saying :

It's also well worth checking the physical side - is the glass moving smoothly, is the cable grotty etc.

I *think* it's the motor; when the window works it works perfectly but it just stops on occasion. A good tug on the window often makes it start working again so I guessed it might be that when the motor stops in a certain position it won't restart.

I will apply the leccy to it directly, as you suggest, and test the output from the box of gubbins. Bugger to get to though.

Si

It's all fine mechanically, but I did wonder where the "stop" sensor part lived, and whether it just detects strain within the motor itself or something a bit more technical. Oh, I know; why not have a look at the workshop manual which arrived yesterday on cd!? Sometimes.......

It's a Nissan Terrano (the bane of my life), btw.

Si

If the window jams (or reaches the end of its travel) the motor can't turn any more and the current it draws goes up. With one system a sensor detects this and cuts the power feed. If the motor is one where the current is being monitored like this either the monitor is too sensitive or the glass is jamming on its way up. You need to be sure that neither of these factors is true in your case.

Rob Graham

Righto, will do. Ta.

Si

It could also be that one of the coils in the motor has fried leading it to run at normal speed when no load is applied but then running slowly under load and/or refusing to start if it stops with the dead coil connected across the brushes, just a brief helping hand is needed to startit. You can only really check this by dismantling the motor and checking for shorted/open circuit coils between the armature segments. If this is the problem then just change the motor.

Chris

Something that surpised me was the way my Punto's service manual says that it detects when it ought to stop.

Apparently there's a microphone and some electronics detect a change in the pitch of the sound from the motor!

Is this unique to Fiat?

I can't see why, given that modern windows use much less powerful motors than once. The ones on my SD1 positively whizz up and down compared to my much newer BMW.

What a strange way of doing it. ;-)

The easiest way is simply to measure the voltage drop in a length of the cable feeding it (or by using a very low series resistance which won't effect performance) - easily done with modern electronics. Really a bit like an ammeter. Once that drop exceeds a certain figure, it means the motor is drawing too much current and gets switched off.

The message from "Dave Plowman (News)" contains these words:

I noticed that getting back into the Montego after the Audi. Apart from being high up, tinny and plasticky, the windows fly up and down so fast.

Fiat tends to have a very unique approach to anything approaching elektrikery, often with amusing or dire results.