Hello, I posted of a problem recently where my windows wouldn't move due to a burned out 5A passenger side door switchpacks fuse. When I replaced the fuse, the windows worked, but the drivers's side window switch started burning. I pulled the window switch out and ordered a replacement. The wiring harness that was a attached looks fine, and the window switch was definitely the source of the burning. My question is if there's something I should be looking for like an over voltage going to the switch box? Or is it probable that something shorted out in the switch in the first place and it simply needs to be replaced? Thanks!

 

Tommy, there's no way voltage to your switch could be higher than battery 12 to 23 volts. To specifically increase dc voltage you'd need a transformer in line, there isn't one. Besides that everything on the same circuit (IOW everything that didn't work when fuse blew) would have seen the same increased / destructive voltage. So don't worry about that.

For the switch to fail like this, it must have seen a lot of heat, which would have been caused by a short circuit allowing lots of current to pass very quickly.

When you have a short like this something's going to fail, we hope it's the fuse. Sounds like you saw the switch heating up.

Normally 12 volts comes into switch, goes into window motor, then to ground. Something allowed enormous current (# of electrons per second) to pass through the switch for it to heat up. We have to track the short circuit down so it doesn't destroy your next switch.

Somewhere between the hot wire (12volts) into the switch, and the motor, something is touching ground. (If the other switch wire went to the motor, there would be resistance, not a short circuit).

Take a volt meter. One lead on chassis screw ( this is grpund); other lead on wire #1 to switch, ignition on. Do you see 12volts?

If so note which wire this is. If not plug into other switch wire for 12 volts.

The other wire should go to window motor. Put your meter on ohms. Measure resistance on this other wire to ground. If low resistance this indicates a short circuit that caused the problem. You must find and fix where this is happening.

Let's hope it's an abraided wire rubbing on metal. Could it be inside the motor itself? Yes but we'll figure it out.

Take off door card. See wire harness that plugs into motor? Unplug it.

Identify the wire from switch to motor. Plug ohm meter into both ends of wire ( by switch and by harness.) Should show nearly zero ohms. One end of meter in switch end, other end to ground. Show continuity? Yes equals short in that wire segment. Find where it touches ground and fix. No? Wiggle wire to ensure you haven't moved/ disconnected the short circuit.

If not found measure resistance at exposed wire into motor and ground. This would show if motor is defective and shorting out.

Tommy let us know what you think. Ask any questions, happy to help. It's tempting to call it a bad switch and just replace it, but that would not explain why the switch heated up. Any short circuit inside the switch would have just opened the window.

As I think that through I was about to type there is a relay that would then trip just like when you reset windows. Tommy after all that typing I'm left wondering how a 5 amp fuse is then involved. As I just said, the windows are protected with a thermal relay . The truth is that without a wire diagram in front of me I can't help too much more. Let me ask others to chime in here.

John

 

Given that the switch is burning without pressing anything, it's possible that it has shorted internally, so replacing it should be OK.

However, you don't want the replacement doing the same, so I'd check that there isn't a short in the loom downstream of the switch or, possibly, the driver's door module.

With the switch removed, hook one wire of a test lamp (bulb not LED) into the driver's side window switch socket brown/white wire.

Now take the other lead and touch in succession the black/ green, black/orange, black/purple and black/red connections.

What you want to see is firstly the LH window drop and then rise, followed by the RH window as you make the connection in the above sequence.

If the test lamp lights without the window moving, then you have a short somewhere.

Here's the relevant snippet from JTIS. 36 (the brown/white wire) connects to the 5A fuse that you have replaced. DDCM is Driver's door control module.




HTH,
Mike

 

Thanks very much for the in-depth responses! Yes, I would like to avoid burning up a brand new window switch, so I will check the readings as per your instructions before installing.

What I cannot answer is what popped the passenger's side 5A fuse in the first place- it may have just been coincidental timing.

Here's the order of events:
1. Battery dies (turns out it was a bad battery), replace battery
2. I notice that windows will not roll up
3. I try every technique I can find to reset the windows
4. Notice that 5A passenger side door switchpack fuse is blown
5. Replace fuse, start car, raise windows using driver's side window switches
6. Notice that something in the driver's side window switch box is burning
7. Immediately turn off car and remove passenger's side 5A fuse
8. Remove driver's side switch box and notice a strong burnt smell

Cheers

 

Are you saying the fuse that was blown wasn't the window fuse? If not, which fuse was it?

According to the wiring diagram both passenger and drivers windows go through the same 5A fuse in the passenger side fusebox.

 

Thanks to Mike, my response wss written as though the switch connected power to the window motor. Diagram clearly shows switch connects to drivers door control module. Which explains the 5 amp fuse to the switch and a relay to the motor. Sorry for confusion. If switch grounds the 12 volts in it would explain short circuit heat and blown fuse. Use multi meter to probe this in burned out switch if you like. Thanks Mike.

Hohn

 

I am still waiting on the switch, probably got tangled up in the holiday mail.

In response to dibbit's question, the fuse I replaced was the 5A passenger side 'door switchpack fuse.' Since both windows worked after replacing the fuse, I guess that was the right one.

I am taking the door off and inspecting the wiring today, hopefully the switch will arrive soon! Thanks

 

Thanks for the help with this. I checked the door wiring and it looked fine, popped in the new window switch and everything works fine now. Cheers

 

Would the same problem on a 2002 XJ8 be solved the same way? Would the color of the wires and their designation be the same? Thanks for any information that can be provided

 

Hi wrd0225,
You would be better posting in the X308 forum (or asking one of our mods to move your post)

In the meantime, here is the electrical guide on Gus' site of everything:
http://www.jagrepair.com/images/Auto.../jagxj2002.pdf

It's titled 2001 in the pdf (as are the 2001 & 2003 files) but it should get you started.
Surprisingly, the colours to the front window pack do correspond with the snippet above (except for one, which may be a typo), but the XJ has 4 controlled windows rather than two. You will need to trace the power feeds etc. as I wouldn't expect the numbering or fuse positions to match.

Good luck.

 

Thank you for replying.