Dashboard Instrument Lighting

[AidanT]

Hi

 

Looking for some advice on dashboard instrument lighting. I have a standard ~Smiths small Fuel gauge which does not seem to illuminate. I have checked the bulb at the rear and this is working but no light would seem to be getting through to the face of the gauge.

 

Does anyone have experience of taking these apart, knows why this is happening or has experienced the same?

 

Thanks

 

Aidan

[Darren Groves]

Is the bulb holder a 1 or 2 wire type? If it's a single wire it's earthed through the gauge, so ensure the gauge has a good earth, if it's a 2 wire then check continuity in both the live and earth. Should it be a green or white light? Some gauges have a little green plastic dome on the inside where the bulb goes, unless that has got very dirty or covered not sure why the light wouldn't come through to the face.

[AidanT]

The light bulb is working fine the light just doesn't seem to be getting through. Is there any issue in taking the gauge apart?

 

Aidan

[JohnD]

Is this the type with the bulb holder a tube that slides into the body of the gauge?

Easily removed, so you can replace, or just see that the bulb is working.

If that is the case and the light not getting through, then short of dismantlind the gauge, remove it from the dash and examine the recess in the gauge in a good light (!), with a probe.

There must be some obstruction - possible your gauge system has a bug (Sorry - it's Christmas!)

 

John

[Ben Caswell]

Some of these gauges have a little coloured plastic dome over the bulb mounting usually green to give a coloured back light. If the bulb has been too powerful or perhaps its just time the plastic may have become discoloured.   

[Pete Lewis]

if you strip the gauge you may find that

 

some are just sprayed a lick of white paint to aid lighting, if you remove the gauge and strip it down you could add some cooking foil to the back 

 

those with the green filters can burn and go black or fall to bits ,  

 

most wont show up much till dark..its old  not very techy lighting 

 

Pete

[mbullyb]

Hi, I have had a similar issue where the backlighting for my instruments were really dim although all bulbs were working. I removed all of the green plastic filters (which most had burnt out), and replaced the bulbs with green LED's that i bought off ebay 

 

http://www.ebay.co.uk/itm/10PC-New-GREEN-E10-10mm-Screw-In-12V-18V-Led-Bulb-Light-for-LIONEL-1447-1447G-GL-/191736146967?hash=item2ca45d6c17:m:msEvLlK0qXp3yu3iCwu4phg

 

Vast improvement

 

Regards

Mark

[AidanT]

Hi all and thanks for the information

 

I have today stripped down the gauge and have found the problem. The original standard bulb had blown so I had replaced it with an LED one. The problem with this is that the led bulb sends light directly ahead of it and not to the sides. The design of the gauge is such that it needs light to come from the side of the bulb.

 

Light directly ahead is just bounced back to the bulb. Anyway light has to go to the top of the gauge and then reflected back as Pete says with where some white paint reflects the light down on to the scale and needle.

 

There was no green filter in mine burnt or otherwise

 

I will take your idea up Pete and add some foil to the white area so more light is reflected and of course revert to a normal bulb or and 'led that has led outputs to the side

 

 

Aidan

[Pete Lewis]

A

sliced bread still has some advantage over LED , they just do not suit many applications

 

good fun messing about though

 

remember classics have this odd conundrum, when you find the culprit and replace it

It never cures the problem !!!!!

Pete

[JohnD]

This problem, and the many responses, reveals something that every poster should consider.

 

First - what you did to the car last - that is the problem!

 

Second - when asking for advice, tell the whole story.   Your original post, Aidan, didn't mention that you had fitted an LED!

  If you had, then all the talk of little green domes and the merits or not of dismantling the gauge would have been unnecessary.

 I can't say if the assembled diagnosticians would have come to the same conclusion at once, but they would have pointed out Rule First!

 

John

[AidanT]

John I agree with your statement however if this forum is used by others with a similar issue then it will cover more than the use of led bulbs

 

Aidan

[dougbgt6]

I got some additional gauges and was disappointed to find they didn't have green light. This was temporarily remedied using green Quality Street sweet wrappers cut in strips and placed around the rim of the dial. I'm embarrassed to say they are still there, and still working.

 

PS Don't put them near the bulb!

[JohnD]

http://uk.farnell.com/kingbright/l-53gd-12v/led-5mm-green-20mcd-568nm/dp/1142554?ost=1142554&mckv=rwyXIqTx_dc%7Cpcrid%7C78108292869%7C&selectedCategoryId=&CMP=KNC-GUK-FUK-GEN-SHOPPING-KINGBRIGHT&CAGPSPN=pla&gclid=CMar586-7ckCFQ26Gwodu-YONg&CAWELAID=120173390000015257&gross_price=true

 

GREEN Leds, 3 pence  each.

 

John

[Gully]

I'm going to be changing my GT6 speedometer for a correct ratio version as I picked one up recently (also the bearings in mine are going). However, I've noticed the oil pressure green plastic 'jewel' in the replacement is dirty and / or damaged - quick attempt to clean it with a cotton bud did nothing. Are these removable without taking the gauge apart, or not, please? The one in my current speedo is fine, so I'm thinking I could swap them over.

 

Thanks,

 

Gully

[Pete Lewis]

This is the small jewel in the dial ?? They do remove but probably mend it to destruction

 

Do a careful test on the old one , before you wreck the replacement

 

if you get involved with changing the dial assy its most important you keep the alloy drive disc and needle in exactly the same position , when you remove the needle do not let the hair spring unwind

cos then youre pretty well stuffed.

tape the disc firmly in a marked position first.like 0 or 30 etc.a known place so you refit the needle in its

removed place on the disc spindle.

 

pete

[dougbgt6]

And, don't touch the decals! They come off on your fingers. Don't ask.  

[dougbgt6]

Going back to the LED lights, Aidan's problem was down to a one directional LED bulb. Attractive as John's LEDs are at 3p each, they would also be one directional.

 

The club shop sell what appear to be multi directional LEDs but I'm a bit confused over the price. The on-line catalogue says white £5.00, green £6.00 (including VAT) but the club shop button says, white and green both £7.80 (including VAT). Confusing huh?

[Pete Lewis]

the online catalogue assumes you are a member , if in the online shop you need to ..erm....log in for members prices 

 

really Doug   ..... you  must try harder   Ha !!  

 

confusion solved  .........where me slippers   or  I'll  get me coat  !!!!

Pete

[Colin Lindsay]

Simple point but one that we all find out the hard way - lights such as the headlamp illumination or oil pressure use 'straight-ahead' leds, but dial illumination needs to throw the light about and so needs multi-directional leds. All easily obtained in any colour of your choice. Even I was able to do it!!

[dougbgt6]

Pete, the thought had occurred to me so I ensured I was logged in, so ya-boo-sucks to you!  

 

Even if I wasn't logged in why does one have white and green the same price and the other a £1 different?

 

And what percentage do members get? If £7.80 is the undiscounted price and £5 the discounted then the discount is 36%. I'll have one of everything if that's right!

[Gully]

This is the small jewel in the dial ?? They do remove but probably mend it to destruction

 

pete

I suspected that may be the case!

 

Thanks all - I'm sure I can live with it

 

Gully

[Stuart R]

These pictures may be of interest, although not directly related to Aidan's problems.  I couldn't see the blue Main beam warning light on my Herald 1200 speedometer and was concerned that it would be an MOT failure.  Instrument back lighting was OK and the main beam warning bulb was functioning.

 

There are 5 bulb holes in the Speedo, 2 for dial illumination which are larger and correspond with a patch of black paint in the dial housing.  You can see that a forward facing light source is mostly going to hit the back of the dial and go nowhere else.   3 holes for the warning light jewels appear to have plastic/rubber hoods fitted that degrade over time and turn to gloop.  I don't know what the hoods originally looked like, but imagine they are there to stop the dial illumination 'leaking' into the warning lights.   I've seen this on both my Heralds and in this instance the gloop had partially obscured the light path to the blue jewelled lens.

 

I cleaned as much of the gloop off, making sure I kept fingers and cleaning cloths away from the painted dial.  If I remember it was pretty solid and could be picked-off easily.

 

Replaced these hoods with some silicone cable sleeving as thought even if it touched the bulb, it should withstand the heat.  The silicone sleeving is braided and so expands a bit and didn't really grip the back of the lens so addded some black PVC tape to keep things in place and reduce any light transmission from the back lighting.  Everything is quite dim, so I doubt that's an issue.  The main beam lens is a very dark blue, so light transmission is pretty poor to start with.

 

Regards,

 

SR

[Mike R]

Hi Stuart,

This is much appreciated - i have the same problem with the blue main beam warning light not showing even though the bulb is fine. Short term i've replaced the standard bulb with a high intensity LED which has meant it is now visible, although very dim. I had planned to investigate at some point when i was prepared to go through the pain of removing the speedo.

Now I know what I'm likely to find.

 

Cheers,

Mike

[Gully]

I successfully tackled the cleaning of the green Jewel light in-situ on Sunday morning using hi-tech workshop equipment - namely lightly moistened cotton buds! Holding the speedo up to the sunlight, all three jewels now shine beautifully

 

Gully