Electric window motor repair- how to

[mk2]

After weekend of messing about, my window is working again. But I don't think I fixed anything at all.

Ok, so one of my Lupos decided recently that the passenger side electric window wasn't going to play any more. It was shut and didn't want to open. All it did is make a click sound every time I pressed the down (or up) switch. This happened with both the driver's and passenger's side window control switches. My first thought was that the Central Convenience Module (CCM) had thrown a tantrum as is so often the case in our Lupos. It affects central locking, window behaviour and interior lights (plus a few other bits). Locks were ok, as was the inside light. So I thought I'd check if I could control the windows without using the control switches- by using the door locks. There's a handy feature on all electric window Vdubs where if you want to open all the electric windows at the same time without getting into the car, you simply insert key into driver's door lock and turn it to the unlock position and hold it there for five seconds. (To close them all you lock it for 5 secs.).

The driver's window opened no problem. Passenger side; Nothing.

By the way, this fault is different to the really common wire rope snapping, the glass clamp breaking loose or the track or pulleys getting jammed (often caused by trying to work the windows when they've been glued shut with ice (or frost). Sticky or slow windows just need some silicone oil sprayed onto the felt window tracks to help them slide more easily.

So off with the door cards. Carefully cut or peel the waterproofing membrane away from the top only (to be reused- essential!). Reach in and unplug the motor connector (not easy). Tape the glass up to the top of the door so it doesn't drop down. Reach up and slightly loosen (but don't remove) the two 10mm glass clamp bolts (also not easy). Gently unhook the plastic cable 'X' stay from the door. Unbolt the five 10mm bolts/nuts and carefully remove the entire assembly. So far all pretty standard stuff. At this point you could spend money and just get another new assembly, swap over and reassemble.

The following pics I took while working show what you need to do to sort out a clicking motor that doesn't want to work. It's all basically just cleaning and testing. I pulled everything to pieces, cleaned a LOT of dust off the PCB and the two sensors, wiped bits of metal off the magnet ring and washed any carbon brush material off the PCB using brake and clutch cleaner fluid. Then put it all back together again. I couldn't find any faults. My guess is that the bits of metal stuck to the magnet ring messed with the output pulses and carbon brush dust, which conducts electricity partly shorted out the components on the PCB. The relay also appeared to work just fine- you can't test it without removing it from the PCB because 12V goes backwards into the circuit (which would damage it). Trickiest bits are unsoldering the PCB without damaging anything and then putting the brushes back in. An extra pair of hands is useful there. I suspect that during factory assembly, they use a plastic 'loading ring', sliding the rotor in place while a thin rigid plastic tube holds back the brushes.

The rest of reassembly is the reverse of dismantling. The easy way out would be to simply swap the motor/gearbox over which was my first choice. But they are unique to Lupos/Arosas; I couldn't find one anywhere (for a reasonable price).

Edited June 9, 2020 by mk2

[mk2]

Update:

Just did another different Lupo with exactly the same symptoms. All you can hear is the relay clicking, but nothing happens when you press the window switches.

Another easier solution...

Once I removed the slider/cable/rail/motor assembly thing, I pulled the motor out, separating that plastic drive spline from the cable drum (that pulls the window up or down). I thought, "I wonder what will happen if I plug it in now, without the cable assmbly attached to it?". It worked. Yes, the motor worked perfectly. Up, down, start, stop. Perfect.

Must be jammed tracks/cable? Assembled it again, and the damn thing carried on working as if nothing had happened. Very odd. Put it back in the door, this time with glass clamped down. It worked again. Normally. Not slow or stiff. Normal.

Back out again. I needed to know why. Then I noticed that the plastic spline gear thing that the motor rotor drives, was slightly warped. The central spline was running at an angle, presumably where it was held shut for ages, as most of the time the passenger window is never used. The only reason it worked again is that when I reassembled it, the splines were in a different position (by pure chance), so there was no angled stress.

Then it hit me. The slight spline shaft angle acts a lock, preventing the cable drum from turning once there's some tension on it- which there will be once the motor drives the window hard up against its stop (at the top).

Solution: Pull everything out of the car as before. Separate the motor from the cable drum. Don't move the window sliders at all. Mark the white plastic splined drive cog (that I've marked 'up' and 'down' in the pic). Run the motor so the plastic worm gear spline drive is 180 degrees out before reassembly. All sorted. The new position should, over the next 20 years mean the thing will slowly unwarp... It should carry on working perfectly now, asssuming the rest of the system holds out. Yay!