Panel Lamps (And Lack Thereof!)

[StrongSpearWorks]

Good afternoon forum,

Last winter I replaced all the incandescent bulbs with LED. Everything has been fine.
However, with the nights drawing in I've just noticed that the panel lamps along the dash (sunroof, heated screen, antenna) left and right (headlamp switch, fog lamps) and the heated seats are no longer illuminated. The lamps for the heater controls are unaffected - I didn't change those over as it was a more involved job.

Fuse is fine (visual inspection and put on the multi-meter).

I mean... it's not life threatening, but it's certainly annoying. Are they wired in series - i.e. one out, all out?

[Laird Scooby]

Originally Posted by StrongSpearWorks

Good afternoon forum,

Last winter I replaced all the incandescent bulbs with LED. Everything has been fine.
However, with the nights drawing in I've just noticed that the panel lamps along the dash (sunroof, heated screen, antenna) left and right (headlamp switch, fog lamps) and the heated seats are no longer illuminated. The lamps for the heater controls are unaffected - I didn't change those over as it was a more involved job.

Fuse is fine (visual inspection and put on the multi-meter).

I mean... it's not life threatening, but it's certainly annoying. Are they wired in series - i.e. one out, all out?

Try adjusting the dimmer a few times and also set it to a higher level ultimately.

They're parallel wired by the way.

[StrongSpearWorks]

Originally Posted by Laird Scooby

Try adjusting the dimmer a few times and also set it to a higher level ultimately.

They're parallel wired by the way.

Hmm... tried that. Looking at the wiring diagram in the green book it looks like they're all connected to a branch somewhere within the centre console. I can't think that two branches have died but all the other things that come off that fused spur are all fine.

Mysteries of 30 year old wiring!

[Ian21401]

Does the OP mean that the illuminated switches have failed? ie: heated seat switches, heated screen/mirror switch etc. He does not mention the instrument cluster or warning lights. IIRC the dimmer slider only changes the instrument cluster illumination, but I may be wrong.

[Laird Scooby]

Originally Posted by StrongSpearWorks

Hmm... tried that. Looking at the wiring diagram in the green book it looks like they're all connected to a branch somewhere within the centre console. I can't think that two branches have died but all the other things that come off that fused spur are all fine.

Mysteries of 30 year old wiring!

I wouldn't put too much store in that diagram being geographically correct, just topologically correct.
Given the three minor switches each side of the steering column all use just the one bulb (of any variety) on each side, i'd investigate those first. You may well find the bulbholders have slipped out of the light guides in the back of the switch panel, likewise on the heated seat switches.

I'd try removing and refitting the bulbs next, if that doesn't bring some life back, try replacement LEDs. Can you remember which ones you got originally?

[Laird Scooby]

Originally Posted by Ian21401

Does the OP mean that the illuminated switches have failed? ie: heated seat switches, heated screen/mirror switch etc. He does not mention the instrument cluster or warning lights. IIRC the dimmer slider only changes the instrument cluster illumination, but I may be wrong.

Good question Ian, i know i have a light guide that operates from one light source to light up the heated seat switches, similar to how the illumination for the three minor switches (up to three anyway) each side of the steering column.



That's the one for the heated seat switches, note the original bulbholder had broken hence my "repairs". Also the reflective silver paint on the outside had chipped off over the years so i masked the ends then sprayed with silver paint.

As for the telltale bulb inside the switches, they had both failed on my switches so i pulled the switches apart and fitted 3mm red LEDs each with a 680 Ohm resistor so i now know when the bum-warmers are (allegedly) active :



The thing with LEDs is because they produce a coloured light, they're less likely to be confused under bright sunlight or similar conditions.

[Ian21401]

I haven’t gone down the LED route. I’ve simply replaced the odd defective bulb when required.

[Laird Scooby]

Originally Posted by Ian21401

I haven’t gone down the LED route. I’ve simply replaced the odd defective bulb when required.

I hate replacing bulbs which was my main reason for going to LEDs, some of teh cheap ones on ebay use a series resistor that is calculated to give not just maximum brightness (usually at about 2/3 maximum current or If) but also maximum current flow (max If) at 12v - most cars runs at ~14V so straightaway the input voltage is 20% higher than designed for, this results in ~50% more current going through the LED than it can handle so often the cheap Chinese "12V" LEDs will fail very quickly.

I turn the dimmer down until the LEDs just start to dim to counteract this these days, except on installations where i've built the LED bulb myself.

[StrongSpearWorks]

Originally Posted by Ian21401

Does the OP mean that the illuminated switches have failed? ie: heated seat switches, heated screen/mirror switch etc. He does not mention the instrument cluster or warning lights. IIRC the dimmer slider only changes the instrument cluster illumination, but I may be wrong.

Morning!
Yes the instruments and warning lights are all still working as normal.
It’s the the lamps behind the accessory switches on the dash have all gone out.

All the new LEDs are in the bulb holders as they were.

It’s a bit of a head scratcher. I suppose the next port of call would be to test the bulb holder for voltage. The green book shows an in-line fuse, but that’s before the branching point so I’d expect everything else attached to be off too - such as the heater control lighting.