Nearside rear window goes down only

Sounds like you may have a failed control switch?

 

For the non-UK, members not familiar with the UK jargon nearside and offside, nearside (n/s) is the left side of the car, and offside (o/s) is the right side of the car.

 

But if the steering wheel in the UK is on the right side of the car, wouldn't the right side of the car be more near the driver than the left? Maybe you have it backwards?

 

I doubt the side of the car is actually all that important, as the circuit is going to be pretty much the same for both of the back door window motors.

It sounds like the "motion limit" circuit is broken. If you open up the door to get access to the window motor (be careful not to get that black mastic stuff all over the place), and then hang a DC (not AC!!!!) clamp ammeter on the +12V power wire going to it, and then run the window down you should see the current go up as it moves normally, and then go up even higher when it hits the bottom. That 2nd rise in current is supposed to tell the controller to turn it off. My bet is that you see the 2nd rise and it doesn't stop because that function in the controller is broken. Is that controller in the motor itself? Don't know, perhaps somebody else here can say.

It doesn't sound like a switch problem - even if the switch was stuck the controller is supposed to stop the window motor at the limit.

 

The 12v battery has been disconnected and reconnected, which should (?) reset any 'auto' window functions, yet the window rolls downward, with no operator input, as soon as the motor is plugged into the car harness...................does it act differently if the window lock button on the driver door controls is activated?

Does the auto up/down feature work on the driver window? The switch on the driver door has an AUTO light on it. Is this light blinking or solid?

 

Lol... Thanks for trying to help me out...

I'll never make sense of the British! I still have yet to understand if my mom's side is Scottish or Irish? They kept shipping my ancestors back and forth to confuse us and it worked. Seems near same with rules of the road right now!

 

I don't know where @ChapmanF is right now, but he's always the smartest person in the room when it comes to window control sensor issues.

 

Most of the times I'm the smartest person in the room on anything boil down to when I'm the only one in the room who's looked in the repair manual, and I have no control over that....

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That's definitely where I'd start with an issue like this. A good scan tool or Techstream would probably be handy, because I bet you can ask it what the condition of the window switch is. If it says it thinks the switch is in the "go down" position, then you know why it's going down, and you look at the switch or the wiring to the switch. Or, if it says it doesn't think the switch is being pressed, then you focus on the wiring to the motor.

 

But...

Shouldn't the motor stop at the limit regardless if the switch is being held down? If the motor keeps running then it wouldn't be the switch's fault, but the fault of the range limit detection circuit, wherever that is.

I just ran out and tried this on our 2007. Holding the switch down for the driver's side rear window, from the driver's seat, with all the fans off, it moves smoothly down to its range limit and just stops. There are no noises like the motor is trying to do anything, even though the switch is firmly in the down position.

 

That seems like at least two questions for the person who will be diagnosing the car:

1. why does the window want to go down at all when no one is pressing the switch?
2. why does it not stop wanting to go down when it's all the way down?

Unless they changed something between the 2006 repair manual I'm looking at and your 2007, they just didn't have a very sophisticated power window system in Gen 2. The driver's window (only) had a pulse counter, with auto up/down and jam protection and reversing. All three other windows are like the ones in grandma's car; the switches connect the motors to +12V and ground, or to ground and +12V, and the motors try to move until you let go. The whole "range limit detection circuit" is a PTC resistor to keep the motor from burning out; the hotter it gets, the less current can flow. The test in the manual is to go hold the switch for 90 seconds or more, and then confirm that it takes a minute or so for things to cool before you can make the window move again.

There doesn't seem to be much more to this system than you'd check out with a multimeter. It sounds like you've got +12 on the green and ground on the yellow, when you'd want to see both grounded when no one is holding a switch. The local switch or the driver's-door switch is probably doing it. Apply multimeter, find out which, and correct.

There's a good 50+ pages in the repair manual on the power windows, including how to test all the switches and the window motors.

 

Normally, two wires for each of the satellite window switches are connected to earth through the master switch (in default position). Each satellite switch (in default position) connects both circuits "straight through to the appropriate motor.

Move a switch at the master, and it lifts one circuit from earth to 12V, and the motor and glass moves. Switch directions, and the connections reverse, as does the window.

There's a 12V feed to the satellite switches. Move one of those switches and a circuit is lifted to 12V. The other circuit remains earthed at the master switch and things move.

It sounds like the "down" circuit for your problem window is remaining at 12V - most likely within the master switch. Disconnecting that switch will disable all the windows (but you can test both circuits to the RR window to confirm that neither is shorted to 12V). Then you can replace the master switch - or connect both of those circuits to earth. That would allow you to test operation of the window from the satellite switch. If that's good THEN replace the master.

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I measured the current going through the big rubber shrouded connector to the passenger side rear door with a clamp DC ammeter (UT210E). Take these with a huge grain of salt because the rubber shroud was pushing hard on the clamp and might have opened the end part a bit.

0 mA window not moving, switch not engaged, clamp zeroed after being clamped on (ignores any background current or magnetic fields)
~23 mA window moving down, switch pushed down
~150 mA window all the way down, switch pushed down
~10 mA window moving up, switch pulled up
~10 mA window all the way up, switch pulled up

I have no idea why the current draw is so different going up versus down. In fact, the up measurements don't make much sense, unless maybe the ammeter didn't want to measure current moving in the other direction.

Anyway, the 150 mA at all the way down was maintained for as long as the switch was pushed down (about 20s), so there is clearly nothing in the down switch position circuit that turns it off, at least not quickly.

I think the 23 mA vs. 150 mA is due to the way the motor itself works. These motors usually have brushes so the current while it is turning will consist of a series of pulses as each of the two brushes lose contact with its respective section of the commutator as they move on to the next. The DC measurement cannot really measure this correctly and just gives some sort of average of the waveform. However, once the motor stops at the end of the range the brushes sit statically on their respective sections of the commutator and that creates a continuous resistive circuit which doesn't change. So the 150 mA measurement should be the actual DC current. In terms of heat the stalled position will be continuously heating the same 2 plates in the commutator, and those could get pretty warm. When the motor is spinning the heat is spread around the entire commutator, so no one part gets too hot, and besides, it only takes a few seconds to move all the way up or down, so the total amount of energy dumped isn't very much.

In terms of figuring this out, unplug the door connector (door has to come apart), determine where to put in +12V and ground into the door side of that connection, and see if the same behavior is observed. If yes, it is probably the door switch, and in any case, there is definitely a problem inside the door. If not, it is probably the driver's switch. Taking the switch apart and cleaning it might resolve the issue, as at least on some cars dirt can get into/under these sorts of switches and jam them into one position or the other.

 

Your amp-clamp technique needs work. The hall effect sensor in the clamp detects the magnetic field that's created by current flowing through a conductor. That field is proportional to the amount of current.

You have to place the clamp around ONE of the conductors in a circuit (+ or -). If you clamp both, the magnetic fields cancel each other out and the meter reads zero. The jaws must be able to fully close, or the (absolute) reading on the meter is useless.

If you don't want to dig down to a specific wire for the power windows, try this. Power up to "ignition ON" - not READY. Place you clamp on one of the 12V cables then zero it. Have a second person operate the windows while you read the meter.

FYI, for typical power windows, I have measured around 7 amps going down and 8-14 amps going up. It peaks at 20 amps when you "stall" the motor at full up or down.

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Well, I did say that I wasn't very confident in the result because the rubber was pushing out so hard on the clamp.

I was expecting to either measure zero amps (for the reason you described) or a current (if the motor was grounded to the frame through the hinges). The measurement was in between: not zero, nor as high as you say it should be for a true current measurement. In any case, I ran the window up and down a couple of times and the numbers were always about the same. Now I have no idea what was being measured, some sort of induced magnetic field, but from where? The meter didn't move, I didn't move, one finger moved slightly (up, down or off the switch).

 

Did you have the meter set for DC amps? I like the UT210E for the price vs cost, but not thrilled that the default is AC amps (& that I have to zero the meter after switching to DC amps- at least in the low amp range).

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