Lights problem
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Discussion

PurpleMoonlight

Original Poster:

22,362 posts

186 months

Friday 15th July 2016
quotequote all
The old Daimler failed its MOT this morning.

The rear and number plate lights aren't working apparently. Is this likely to be a fuse or something more sinister?

interloper

2,747 posts

284 months

Friday 15th July 2016
quotequote all
I would guess it's probably an earth lead come loose, I think it's unlikely to be a fuse.

Allan L

799 posts

134 months

Friday 15th July 2016
quotequote all
I take it your "old" Daimler double six is one of the modern Jaguar sort!
I can't remember what the rear/numberplate lamp arrangement is on those, but they probably use the bodywork as earth return, so corrosion where the lamps mount is best bet.
If they have an earth lead maybe it is loose as suggested but if not perhaps you should fit one.
ETA Could just be bulb failure of course.

PurpleMoonlight

Original Poster:

22,362 posts

186 months

Friday 15th July 2016
quotequote all
It's from 1993.

I did have to unbolt the electric aerial and move to one side earlier in the year to fit a new grommet so I might have dislodged an earth wire I guess.

TooMany2cvs

29,008 posts

155 months

Friday 15th July 2016
quotequote all
PurpleMoonlight said:
The old Daimler failed its MOT this morning.

The rear and number plate lights aren't working apparently. Is this likely to be a fuse or something more sinister?
Have you had a multimeter on it yet, see how far 12v is getting on the way to the bulbs?

It can't be anything too serious if they were working before you took it for the MOT.

PurpleMoonlight

Original Poster:

22,362 posts

186 months

Friday 15th July 2016
quotequote all
TooMany2cvs said:
Have you had a multimeter on it yet, see how far 12v is getting on the way to the bulbs?

It can't be anything too serious if they were working before you took it for the MOT.
I have no idea what a multiwotsit is.

I don't know when they stopped working. They were a year ago though obviously. I don't use the car in the dark or during winter!

medieval

1,499 posts

240 months

Friday 15th July 2016
quotequote all
Could I suggest just sand paper finishing the brass connectors to achieve a cleaner circuit - has worked for mine in the past if not something more general.

Kind regards

PurpleMoonlight

Original Poster:

22,362 posts

186 months

Saturday 16th July 2016
quotequote all
Hmmmm, this is confusing.

I'm not very mechanically minded so forgive me if any of this sounds silly.

Indicators, fog lights and brake lights all work okay.

Number plate and rear lights not working.

Number plate is on the boot so has separate cables to the rear lights.

I found the earth for what appears to be the number plate lights and cleaned that. I can't find the rear lights earth.

The rear light bulbs don't seem blown although one is a little corroded and I can't remove it from the housing, I didn't want force it too hard in case the glass broke.

I haven't looked at the number plate bulbs as they appear to need the removal of a panel, I guess I could though if absolutely necessary. There is some corrosion around the number plate lights.

Any suggestions gratefully received thanks.


grumpy52

6,055 posts

195 months

Saturday 16th July 2016
quotequote all
I would think that when you had the rear light out to fit a new grommet you have disturbed the connection for the rear lights ,it will be the power feed ,probably one feed for the tail and numberplate lights . If it was an earth problem you would have other lights glowing due to the power finding its way to the nearest earth ,this is why you see random illumination of lights or pulsing tail lights when indicators are used .

PurpleMoonlight

Original Poster:

22,362 posts

186 months

Saturday 16th July 2016
quotequote all
If it's a power issue then the connection would need to be somewhere around behind the rear seat as that is the only point the two sets of cables meet.

grumpy52

6,055 posts

195 months

Sunday 17th July 2016
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You mentioned moving the electric aerial earlier, is this not behind one of the tail lights ?
This is the area that I would start the investigation from .

PurpleMoonlight

Original Poster:

22,362 posts

186 months

Sunday 17th July 2016
quotequote all
Yes it's housed on the right rear wing.

There are indeed loads of wires in that area but I can't see anything detached at all.

I can see the logic of both sets of lights having the same power source as both are turned on by the same switch on the dash, and that I may well have dislodged something but I'm struggling to see where. Frustrating. Grrrrr.

tapkaJohnD

2,000 posts

233 months

Sunday 17th July 2016
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Purple,
Extend your image of the logic. See that cars have a "wiring diagram" that tells you which wire goes where, and that each wire is colour coded.
The convention is a British Standard, BS-AU7a 1983, and lists base colour first, stripe along it, the "tracer" second.
See: http://www.mgexp.com/article/lucas-colours.html
The number plate light wire may be red with black trace.

Find a wiring diagram, the Haynes manual does it well.
Then buy a multimeter, so that you can test for good/bad earths, and if a voltage is present in a given wire.

Good luck
John


imagineifyeswill

1,250 posts

195 months

Sunday 17th July 2016
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most vehicles have seperate fuses for left and right so would doubt its a fuse problem. Does your car have the big fuse box with relays and ECUs in the boot, if so there is a seperate lighting control module in there and thats where I would be looking for the problem, a replacement unit is only £100.00.

TooMany2cvs

29,008 posts

155 months

Monday 18th July 2016
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PurpleMoonlight said:
I have no idea what a multiwotsit is.
Get one.
https://www.amazon.co.uk/dp/B0001K9XKW

Without one, mucking about with old car electrickery is just an exercise in masochism.

For this, all you need is to put it on 20v DC range, stick the red probe on the bit that should have electrickery and the black probe on the body, and see if you have got electrickery. There's much more advanced things to do with it, but that's the easiest, simplest, and most useful.

Yertis

19,707 posts

295 months

Monday 18th July 2016
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I think a test lamp might be a bit more use in this case. I'm reasonably competent but my multimeter has so many functions I find myself using the wrong one when I'm trying to work quickly.

melhookv12

961 posts

203 months

Monday 18th July 2016
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If it's the x300 shape then it's probably the wiring loom from the car to the boot lid. It runs up the right hand hinge ( viewed from the rear of the car ). After constant opening and closing the wires break.

PS should of posted in jaguar section, would of got an answer alot quicker mate 😉☺

imagineifyeswill

1,250 posts

195 months

Wednesday 20th July 2016
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That would sound right if it was just the number plate lights but tail lights arent working either, I would be looking at the lighting control module.

PurpleMoonlight

Original Poster:

22,362 posts

186 months

Thursday 21st July 2016
quotequote all
imagineifyeswill said:
That would sound right if it was just the number plate lights but tail lights arent working either, I would be looking at the lighting control module.
Bingo!

Luckily, I have a local classic jaguar mechanic who services the car. Although the MOT tester did not state it as a failure, the mechanic suggested checking to see if the front side lights are working and if not then it's likely the lighting module. They are not working either.

I have now ordered a NOS lighting module.

I won't be able to get it sorted for the free re-test but that's the price of classic cars sometimes I guess. biggrin

imagineifyeswill

1,250 posts

195 months

Thursday 21st July 2016
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The last time I needed a lighting control module it was available next day from Jaguar, £100 vat and its a 10 minute plug and play job to fit.