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lights problem

Posted: Sun Jan 27, 2019 1:09 pm
by keithj
If there is a prize for asking the most daft question I think I am about to qualify. The panel lights and map light don't work though most other things do. There doesn't seem to be power to either switch so I am suspecting the main light switch but the wiring doesn't seem to line up with either the 3 or 4 position switch in the wiring diagram. The switch has 4 positions if you count off (off. side, head fog) but looks more like pictures of a 3 position. While I can count to 4 how do you tell which it is?

Re: lights problem

Posted: Sun Jan 27, 2019 4:37 pm
by classiclife
Hello Keith,

Is this an issue that has now occurred or inherited ??

Hopefully you have a Robert Cantwell size A1 coloured wiring diagrams to hand - if not worth purchasing; as to read the wiring diagram in either the handbook or WSM you need at least the eyesight of a Peregrine Falcon !!

This wiring issue is a case of elimination process.

I take it the switch turns on the sidelights, headlights and fog lamps when the switch is placed in those corresponding positions ?? This will also include illumination of the rear lights plus the number plate light - if the answer is YES to these then I think it is fair to say the light switch is working correctly.

If the answer is NO then it is LIKELY the switch is at fault or power to the switch is not occurring; but from what you say there appears to be power.

If we accept the switch IS working then then the issue must be a LIVE WIRE problem, because the map & panel lights DO NOT share the same earth - the map light has a separate earth.

The panel light switch is fed LIVE at point 4 from point 1 of the main lighting switch.
The panel edge lights are then supplied from point 7 and the panel lights from point 8 from the three position panel switch - this being off, dim and bright.

The panel and map lights run on a separate set of wires and are not linked other than their common point at the main light switch.

In order to check the live to both of these you will need o carry out a continuity check with a multimeter or at least a test lamp.

Do not overlook a faulty bulb / contact on the map light and with regard to the panel light issue this may point to the panel light switch. The best way to check that is to bypass the switch and link a live wire from the battery (best) direct to the common wire which connects to point 8 on the panel light switch. If the lights come on, as I expect they will, then the panel light switch is at fault.

As for the map light (if not the bulb) then again you need to bypass the switch to ascertain if that is the problem and work back from there.

May seen confusing, but the above will assist you to a successful conclusion hopefully.

It really is a logical process of elimination - whilst carrying out the checks ensure the earth connections are earthing properly.

Hope the above assists ??

Regards.

Richard.

Re: lights problem

Posted: Sun Jan 27, 2019 5:15 pm
by keithj
Thanks for the advice. The problem is inherited having only recently taken ownership and am gradually sorting the various issues. All the exterior lights work OK as do the courtesy lights. The confusion is around trying to match what I see on the back of the switch with the wiring diagram both in terms of connectors and the colour of wires. As you say falcon-like eyesight is required, which I don't possess. Where do you get the coloured diagram you suggest? A quick google didn't reveal a source. In the meantime I will do as you suggest and try to bypass the panel light switch as an experiment. I thought that having two duff switches too much of a coincidence hence wondering about the main light switch.

Re: lights problem

Posted: Sun Jan 27, 2019 5:51 pm
by Zbigmak
Maybe this may be of assistance.
Please see attached.
George

Re: lights problem

Posted: Sun Jan 27, 2019 6:45 pm
by classiclife
Hello Keith,

Robert Cantwell's details are in the Driving Member - he and his wife cover the Hampshire section of DLOC.

I dropped him an email and ordered a laminated colour wire diagram - small cost + p&p but worth every penny IMHO.

Regards.

Richard.

Re: lights problem

Posted: Sun Jan 27, 2019 6:50 pm
by Christopher Storey
I think this car is a V8 saloon, so the diagram supplied for a SP is not quite the same . The mark 2 Jaguar/Daimler main light switchusually has 7 screw terminals on its rear . Number 3 should have a red wire going to the map light switch , a red to the side and tail lights, and a third red going to terminal 4 on the panel light switch. It will also have a red/black to 2 , a blue to 7 , a brown /white main feed to 4 and probably a green to 5 .The map switch should also have a purple/light green wire going to the middle terminal. The panel switch should have the red already mentioned to terminal 4 , another red to terminal 7 ( for the panel edge lights ) and several red/whites from terminal 8 via a multi connector or similar to feed the individual instrument bulbs

Complicated, but I hope it helps

Re: lights problem

Posted: Mon Jan 28, 2019 8:46 pm
by keithj
Thanks for all the help. I'm not sure that I fully understand the wiring but by undoing a couple of previous owners bodges and replacing what seems to be a broken link to the panel light switch everything now seems to work. On to fixing the horns next .....

Re: lights problem

Posted: Mon Jan 28, 2019 9:12 pm
by classiclife
Excellent Keith, well done.

Always a great feeling knowing progress has been made.

Good luck with the horns !!

Regards.

Richard.