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TD5 Disco Leccy question


Les Henson
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Got a problem with the drivers window stuck in the up position. The relay clicks when the button is pressed for up or down, but nothing happens. I swapped front switches over, and the switch operates the passenger side fine. I did a comparison test with the passenger door - one wire becomes live when the switch is operated 'down', and the other becomes live when the switch is pressed 'closed'

On the drivers door, only one wire becomes live for the 'closed' position, but the other remains dead for the 'open' position. As the switch is ok, I would assume that it's a faulty relay? The relays appear to be located behind the glove box, but I can't figure out how to access them. I was going to swap one of the good ones for the possibly faulty one as a test. Does anyone know how to get at the relays?

Thanks.

Les.

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The motors are driven directly by the BCU, no relays in between, 'cause the BCU needs to measure the current to avoid trapping someone's head when lifting up the windows.

Here's the diagram:

post-1725-1238681733_thumb.jpg

I see three possible causes:

1. the BCU is faulty

2. the window mechanism is blocked

3. there's a current flow to the ground (short circuit) on the wire that doesn't turn "live" when supposed to anywhere on the way between the BCU and the motor or in the motor itself.

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Thanks Cipx2. I take it that the click is an internal relay within the BCU that can't be replaced/tested? If the winder motor was faulty, do you think that it might give the BCU wrong information and then give the symptoms I describe in my first post? It seems that the two wires to the motor are either both lives - dependant on the switch position, or swap live and earth - dependant on the switch position. I was wondering if it would be possible to unplug the motor and test it seperately with a feed directly from the battery?

Les.

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Here are some quick answers:

- yes, the clicking relay must be in the BCU; don't know if it can be opened and the relay replaced; either that or get another BCU from e-bay, not so expensive; but, before that, you should test it

- if the motor is faulty you should get "live" on each wires with the motor disconnected (remove the plug from the motor) - that is to remove the faulty bit (the motor) from the circuit; I don;t know how you did the test for "live" in the first place so, if you didn't disconnect the motor, repeat the test with it disconnected.

- yes, you can test the motor by feeding it directly to the battery (be prepared for a shortcircuit or use a fused 12V feed)

Also:

- if you get "live" on each wire with the motor disconnected, you can use a 15W bulb in place of the motor to see if the BCU can handle this current flow as it should (the motors draw 1A); you can also connect the passenger side motor to the driver's side wires but this means running some wire across

- you can reach for the corresponding connector on the BCU, disconnect it, identify the pins on the BCU and test for "live" directly at the BCU's output (same, as above, use a 1A load after and if you get "live" on both pins).

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It's worth pulling the BCU apart and checking inside for dry joints, I had this on one of mine recently with one of the connections on the circuit board where the relay is soldered in. A quick dab round with the soldering iron and some fresh solder cured it in my case.

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