Door lock system and right headlight not working
 

I am going to start a thread on this, as I suspect it will get really interesting. This is on my wonderful 92 Sov. I have been using the car for a couple of weeks now and didn't initially notice a problem (not to say it wasn't there, just didn't notice). This week I noticed the door lock system wasn't working from the front door lock knobs. I didn't think much of it. Then, I drove it to work and noticed both a bulb out lamp and a fuse lamp on my dash. Still not too worried, but odd in their concurrent appearance and apparently being unrelated. The little bit of testing I have done so far shows that with front windows down, pushing and holding the lock button on the dash raises the right front window and releasing that button clicks the left front window as if to close it. As stated in the title its my right headlight and the fuse for the door lock system. I put a new bulb in the headlight but no joy there. I am suspecting mice in my passenger knee bolster. Anyone want to start up a pool? I have a dollar each on mice and bad solders......

On Very Slightly further testing, I realize that the windows and sunroof are supposed to close as part of the locking system. (Dopeslap.) Not sure why the drivers didn't go too now that I see that....

Jerry:. An interesting problem, but you will have a much more accurate and informed response if you post this in the correct forum. This forum is for the Series I through Series III XJ cars...your car is what might be called a "Series IV" (and it is commonly known by the factory development code XJ40). Your car is entirely different from those covered in this forum with not a single nut, bolt or trim piece in common. So you are looking for the XJ40 forum.

PLEASE IGNORE THIS. *I* am the one in the wrong forum. Not sure how that happened but I have only had one cup of coffee this morning, so that is my excuse...

Actually Gregory, this isn't the XJ40 forum at all, but the forum for the nuts (and bolts) driving the Jaguar brand of cars, some of whom have a hard time loading cars onto their various ferries.

april 1st 2019

Larry

Are you suggesting the old "Loose Nut behind the wheel" excuse?
Wait a minute.... Series IV? I like that! Maybe I'll start using it.....Although, series IV might be 88-90, and series V might be 90-92. OY Gevalt!
In any case, I am making "relatively" huge progress on the 66 so I have just set the 92 aside for a moment. I had another look at it today and still dont see anything obvious. Leaning toward bad solders at this point, but who knows....

"""""URGENT UPDATE """"""" Light problem seems to have been the fog light. All bulbs are good and No Money was spent! The clip that holds the bulb in had slid sideways and was causing a ground to blow the fuse...... No movement on the door locks, although no evidence of mice incursion has been sighted.... more at Eleven....

I have located and opened the door lock module. I dont see any obvious problems beyond antiquated technology. That is, no burn marks or blown up parts. Can someone show me the wiring diagram for the module and maybe how to test it? As it is, pushing either front door lock knob or the dash button will lock the fuel flap and the trunk, but no doors. There is no unlock at all. My research shows this part is Not located on the Moneyfunnel, so I cannot swap to test. Sad face. Thanks!

Hi Jerry,

Unfortunately the Electrical Guide doesn't show the internal circuits for the Door Lock Control Unit, but it does show the system schematic:

https://cimg4.ibsrv.net/gimg/www.jag...4534bc81bb.jpg

And the previous page lists the inputs and outputs for the Control Module:

https://cimg8.ibsrv.net/gimg/www.jag...05883e3db7.jpg

This list is probably sufficient to test the module. It appears pins 3 and 4 connect to the actuator motors via Purple/Pink and Purple/Orange wires. A voltage pulse is sent to the motors, and the polarity of the pulse reverses to turn the motor in the lock or unlock direction.

However, since your trunk and fuel flap are working, your Control Module must be working because all the motors are connected in parallel to the Control Module outputs. So your suspects are the wiring to the door actuators or the actuators themselves. You can test the actuators by pulsing them with a 9V battery.

The actuators contain tiny little electric motors and gear sets that are known to sieze up when the grease hardens over time. They can sometimes be resuscitated with a good cleaning and relubrication. Somewhere in the Jag-Lovers photo albums there's an album by a member who successfully cleaned his motors and even found a source for replacement motors.

You can download the Electrical Guide at this link if you don't have it:

Jaguar XJ40 Electrical Guide 1991-1992

Cheers,

Don

Thanks Don. I was thinking about the partial locking thing. I had used the door locks last fall. At that time everything was working correctly. I am hoping for a one wire break for all the doors with the possibility of a separate wire to the rear which remains good... I notice too that the "panic" switch on the dash is not shown for 92, but is shown for 93-4 in the Haynes book.

Since the weather is for **** today, I am tinkering in the garage. Taking Dons suggestion of wiring colors I determined that I could "hot wire" the door lock system with jumper wires. Then I considered Larry's Oft Repeated mantra of reflowing the circuit board connections. Viola! My locks work! Thank you guys for your patience and presence. Two unrelated problems. No Dollars spent and only about one actual hour spent on repairs. Yay!!!