XJ Power Window Circuit Troubleshooting

A fellow Jaguar owner recently asked:

"My right side front door window came out of the track resulting in it jamming. After a few cycles of trying to free it up by alternate up and down selections on the switch, something clicked and there was no more power to the switch. I have succeeded in reinstalling the window in its track, but not in getting power back to the switch so I can close the window.

There are no blown fuses in the fuse block in the passenger side footwell, the driver side footwell, or the auxiliary fuse block under the hood on the left side of the engine compartment, nor is the in-line fuse by the battery blown. There is continuity between ground on the car and the ground terminals in the connector to the switch. Threre is no +12v on the connector to the switch at any terminal. The right side rear window worked before this incident and does not afterward. It's switch connector also has continuity to ground at the proper places, but no +12v. The left side windows work fine, as does the sunroof.

What am I missing? Thanks to any who can enlighten me."

The Series III power window and sunroof circuit is protected by two circuit breakers. One breaker protects the left side windows and sunroof circuit, the other breaker protects the right side window circuit. Your circuit obviously got too hot and tripped the breaker.

The breakers and the relay are located at the right hand component panel. The relay round and at the extreme right side of the panel. The breakers are square, with two terminals on top, and mounted lower on the panel.

Here's a circuit description and diagnostic quick-reference:

• White/pink wire at relay terminal 85 -- voltage with key "on"
• Brown wire at relay termianl 30/51 -- voltage at all times
• Red/slate wires at relay teminal 87 -- voltage with key "on"
• Black wire at relay terminal 86 -- ground through lock-out switch

Note that the lock-out function (through the console switch) operates by simply removing the ground to the relay, thus rendering the relay inoperative.

The red/slate wires are output to the switches. From the relay the wires go to the two breakers. With the key "on" verify that voltage is present on both sides of the breakers. If not, the breaker is "open" and that portion of the circuit won't work.

The relay terminals should be checked for cleanliness and security as many problems can solved with a few minutes attention here.

If the circuit appears to be fundamentally in order but a window or windows don't operate it is very likely that the switch is faulty. In nearly all cases the switch contacts are simply dirty. After removing the console cubby box and the plug-in at the rear of the switch, the switch can be pushed out through the console after squeezing the tabs on the sides.

Many owners sucessfully disassemble the switch (keep track of all the bits !) and clean the contacts with a pencil eraser or contact cleaner. Many others report good results by simply spraying liberal amounts of aerosol electrical contact cleaner through the small holes in the switch casing.

This circuit, by the way, is not fused.