Technical Window Motor Fuse Blowing

[littles]

Hello,

I have a 2007 2.3 120 Multijet Ducato with an intermittent issue with my passenger window motor. The window motor fuse keeps blowing and I could use some help diagnosing it.

The fuse never blows when the window is moving. I only notice it has blown when I go to open the window or try to close an open window. The length of time it takes to blow the fuse varies, it doesn't seem to be related to whether the passenger window motor is used or not.

I tested the earth pins for the passenger switch and window motor connectors and both appear fine. The passenger switch and window motor connectors both have 12V on their power supply pins. The Up and Down control pins on the window motor connector have 12V as expected when the passenger switch is moved.

The passenger window seems to go up and down at a similar rate to the driver side window so it doesn't seem like the passenger window motor is struggling or there's debris in the window track.

Other items I still need to check are whether there's a short to ground, a faulty relay or an issue with the driver side switch? I also haven't checked the continuity of the motor inductor because it's difficult to access.

Has anyone had a similar issue before that could recommend my next steps for troubleshooting?

Thanks

 

[Anthony489]

Hi

Those 20 Amp fuses take plenty of current to blow, either a stalled motor running for a long time (which you have discounted) or an intermittent short to ground. My first suspicion would be a short to grounded metalwork from the loom where it crosses the door hinge and is subject to movement and flexure.

I attach a marked up schematic from elearn. Bear in mind that RHD vehicles may differ in detail.

 

[Communicator]

I have not suffered from this problem, but chafed cables where they enter the door arenot unknown. This could account for the intermittent nature of the fault.

 

[littles]

Thank you both for your replies.

I think the issue is a short to ground alright. When I open and close the passenger door a number of times, the fuse blows, even if the window motor isn't ran.

I checked the cables in the door hinge and no visible damage. Similarly, there is no damage to the cables running in the door itself.

My next step is to remove parts of the dash to check for damage where the loom enters the van.

 

[Anthony489]

Hi

For easier faultfinding, try connecting a 12 volt bulb (for example a tail light) in place of the fuse. When you waggle the door or manipulate the loom(s), the bulb will immediately light up if a short occurs. Altenatively if you have a multimeter with a continuity beeper, connect that between the "downstream" side of the fuse holder and earth (with the fuse removed). You will get a beep for a short.