In this forum there have been questions with the same subject/problem. I’ve read most of them and tried the solutions suggested there on my own car, a LHD European spec car from 1992. The interior and puddle lights are on all the time. Pulling fuse #3 will kill the lights but also the radio, aerial and the electric mirrors.

I checked the aerial motor and pulled all the leads from the relay. I pulled all the doorswitches from the pillars and checked them and ground with a PowerProbe. All seemed normal. If I engage one of the door switches I notice a slight increase in light intensity of the interior and puddle lights. That is also the case when pushing the interior lighting switch.



I have tried to make any sense of the electrical diagram. As far as I can tell from this diagram 12V power comes from the top to fuse A (fuse #3 I presume) and goes from the fusebox to a connector C. What I find puzzling is key switch 38a which is said to be part of 38, the ignition/starter switch. What is its function? 20 = puddle lights, 280 = interior lights, 59 = interior light switch, 21 = doorswitch, 335 = interior lights delay BUT ONLY UNTIL 1983 so not on my car.

If all would be normal and I pull one of the doorswitches and measure voltage on this switch what am I supposed to see? 12V on one end end ground on the other but 12V on both when switched is engaged (door open)?

How is fuse C integrated in this diagram? Does it feed 12V to the same interior lighting harness as fuse A?

Thank you for thinking with me and hopefully shed some light.

Olav.

 

I'll have a look at my diagrams later and do some mulling.

I think your diagram might be confusing the issue. First, when the delay unit was eliminated there were changes to the circuit that I don't think your diagram shows. There were more changes in 1986-87. And, since yours is such a late car, I wouldn't be surprised if Jaguar made yet more changes. Tech info/documentation is very scarce for the late cars

Cheers
DD

 

what model diagram is that picture?

 

Partnr is AKM9006 edition 2. It doesn’t say when last edited, first publication was 1985.

 

If the book is nothing to go by how should I proceed. Whatever the layout, there is an unintentional ground somewhere. Is that after the interior light, either left or right, up until the doorswitch or could it also be in one of the doors after the puddle lights. If one puddle light makes ground do all interior lights stay on?

If all would be normal and I pull one of the doorswitches and measure voltage on this switch what am I supposed to see? 12V on one end and ground on the other? And 12V on both when switched is engaged (door open)?

 

I would check all the door plunger switches one by one, what else could it be? If pressing the plunger does not shut the lights off, the switch is bad.

 

As you can read in my first post I did all that. There is a ground somewhere before the doorswitches. Doorswitches are fine.
Another ground issue has arisen. The brakefluid level warning light is on even when connectors to the fillercap are disconnected. Same symptoms. As far as I can tell the wires black/yellow and black run all the way to the rh side of the firewall and go through it into the cabin. That is where I lose track but am very hesitant to dismantle the entire dashboard. I find that scary.

 

if the wires run to the passenger side and thru the firewall, then they go to the passenger side fuse box or components. In that case, removing the knee panel under the dash gives access to many components and wiring, fuse box, etc. No need to remove the dash cap.

 

I just checked this on own car. I used the passenger door switch to avoid further mysteries that the drover's door diode might cause

Door open (switch plunger out)
Both side of the switch are ground

Door shut (switch plunger in)
One side of the switch ground, the other side 12v "+"

Cheers
DD

 

I was convinced that the unintentional ground had te be somewhere behind the facia and I was in no way going to take that apart. The brake fluid warning light was also playing up and 12V could no longer be detected at the brake fluid level switch. I traced the wites down from the switch all the way to the rh side of the engine bay. The yellow/black wire runs against the bulkhead from left to right and disappears into the cabin by means of the three white rubber connectors mounted right of the abs unit. From the connector to the brake fluid level switch there was a good connection. So I gave up. I would remove all 6 lightbulbs in the interior and that would be it. Reinstall fuse #3 and the radio and antenna would work again properly. I started on the rh side and when the 3 bulbs were removed I shut both doors to work on the other side when I noticed the interior lights going off. Reinstalled puddle light front right door; all still ok, reinstalled b pillar light; all ok, and finally the puddle light from the right rear door was the culprit. The fault was either in the bulb holder of which the contacts were mangled or it was the speaker nit being connected and the contacts hanging loose. Strangely the brake fluid level warning is now ok too. Don’t ask me why.

Thank you for thinking with me here. I hope this will be usefull for anyone else in the future.