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MG MGB Technical - make dash glow brighter?

Anybody else suffer with poor dial illumination in their MGB? My 67 roadster is very dim on the speedo in particular - has anybody successfully uprated the bulbs or performed any sort of cleaning or modification to the dials themselves in order to let more light in? Do standard bulbs just fade away after so many years? Any help would be appreciated.
Thanks
Martin Port

A number of options

The contact area in the dimmer get dirty. You can either by pass the dimmer, open it up and clean it, or replace it.

The lights shine into the instruments from round the edge. Some times the become partly dislodged and just need to be put back properly. They shine into the instruments through "windows" which become dusty and may need cleaning as may the surfaces inside the instrument.

Some people fit uprated bulbs. Try cleaning first.
David Witham

Another possible cause is that the interior of the gauge case is yellowing. Most are painted a bright white which tends to yellow over time. As stated in the previous post, the light comes from the rear through slots around the gauge edge. Most of this light is indirect reflection from the case. A good cleaning or repaint will help a lot.
Bill Young

If your car has a reastat, bypass it. Clean the lense, pull the speedo and repaint the inside of the can the btightest white you can find. Then upgrade to halogen bulbs and you instruments will be as bright as modern cars. Don't know where you can find the halogen bulbs on your side of the pond, but here in the US the can be had from The Little British Car Company. A websearch will yeild their website
gerry masterman

Bypass the rheostat!? Sacriledge! They were always like it. Just get used to where the needle is pointing and don't expect to be able to read the numbers, that is what analogue instruments are for.
Paul Hunt

All suggestions (other than bypassing the rheostat) are good ones. Brighter halagon bulbs are available from LBC Co. in the US <http://www.lbcarco.com/> however, cleaning the instrument faces and repainting the interior of the cans and cleaning the rheostat will do wonders for the illumination of the instruments. The rheostat is easily disassembled and cleaned by carefully bending the three tabs back and removing the back. There is a circlip around the shaft that is removed to get the slider out. Once disassembled, scrub everything well with hot water and detergent, rinse well and blow all the water out and then put all the parts in an oven set to no more than 250°F (or the corresponding figure for Celcius) to dry everything out well. One can also use a heat gun for this if the wife objects to things automotinve being placed in her oven. Lubricate the shaft with light oil and reassemble it in the case. Lubricate the resistance wire coil with some switch lubrication like Cramilon and reassemble the whole rheostat. You will have many more years of good illumination by doing this. Good luck - Dave
David DuBois

Martin,

Bulbs DO blacken over the years.

So fit new bulbs - I would not uprate them as they will overheat.

Check the voltage at the bulbs - bad connections may knock off 2 or 3 volts!

The rheostat can be "revived" by turning it repeatedly from one side to the other to clean up the track and wiper.

Despite what others say, the speedo and tacho are internally lit - it is only the small instruments that have exterior bulbs.

Better illumination for the speedo & tacho can be achieved by sticking aluminium foil inside the case - much better than paint.
Chris at Octarine Services

I just painted the inside of my dails gloss white.

But the dials of my Austin Westminster are painted the same 'blue' as the B's but it's dials are very readable, I wonder if it uses a larger wattage bulb.
Cecil Kimber

"All suggestions (other than bypassing the rheostat) are good ones."

David,

Why is bypassing the rheostat not a good idea? At maximum, the gauges are just barely readable at night, so the rheostats on most cars stay in just that position. Bypassing the rheostat eliminates one more source of potential trouble, with no harmful side effects that I can think of. Does anyone actually turn the lamps down?

On my TR6, I removed it altogether and put a clock in it's place - much more valuable than the rheostat.
Dan Masters

I bypassed the rheostat on my V8 conversion with a '74 dash and have had no problems.

I installed a new Moss dash and cut out the hole for the rheostat before realizing I could bypass it. Ended up putting in a "low-oil pressure" light in the hole. Looks factory to me.
Simon Austin

I'm planning to eventually replace the rheostat on my '65 with a push-pull switch and fit the knob from the rheostat to it. Noone will be able to tell the difference, I will still be able to turn the lights off (why the need I don't know) and the old rheostat will never cause voltage loss again.
Steve Simmons

Martin,

LEDs would be a way forward.

Paul
Paul

The advice about servicing the rheostat is helpful. A word of caution about halogen bulbs.

The dimmer is there to lessen interference with night vision - the only other way I know to prevent interference is to light the dials with red light or get a younger pair of eyes. If you are past 30 the recovery time of your eyes will be slowing down - and anyway perhaps you will know most of what you need to know from your ears and the seat of your pants.

Simon's low pressure oil light was used in the RV8 (hope it's red) - the only other warning light worth thinking about is temperature.

If it's a shopping/down to the beach car - what the hell - if it's a driving car - it's worth up-dating and lighting is high on my list.

Navy experience FWIW

RW
RMW

"rheostat can be "revived" by turning" Sometimes. On three cars with dodgy rheostats they have all been of the printed circuit type with the thicker tracks burnt out, which results in a dimmer glow than should be be at maximum (a relative term) brightness. Replacements are flippin' expensive. The thicker tracks are at the 'brighter' end of the adjustable range which is where the greatest heat is dissipated. If you have it turned to maximum brightness and vibration shakes it just off this, you probably won't notice the slight dimming, but the rheostat is taking a pounding, and when it burns out you *will* notice the dimming.

One use for a rheostat is to turn off the dash lamps when parked and save all of 10 watts of drain on the battery.

A Mini I once drove had orange dash lamps, with no dimmer or switch that I could find. They were so bright I had to cover all of them with a piece of card so I could see where I was going on an unlit motorway. Whilst my 89 Celica has brighter instruments than my Bs, and a rheostat, I have never felt the need to reduce the brightness like I did with that Mini.
Paul Hunt

I did use a red warning light. Picked up the unit in an auto parts shop. Simple enough; light, housing and terminals all one piece. I used one of the "star-type" copper washers that are used to hold in the turn signal, high-beam and ignition lamp sockets.

For the sender switch, I used one off a TR6 (I know, a Triumph part in an MG but it works) and screwed it into the oil-pressure terminal that used to contain the switch for the anti-run-on solenoid. I think it's set to come on about 5 psi.

Hopefully I'll never find out for real.
Simon Austin

Just thinking about night-vision comments... at my previous job we built equipment for the US navy and they insisted that we used orange, not red, LEDs to backlight our displays on the grounds that this didn't impair their vision when used in dark submarines.

Odd that there's a colour discrepancy between UK and US navies :o)

How about a few loops of electroluminescent wire around the outside of the dial? All the light would then shine inwards onto the dial, which is what the bulb is supposed to do.

fwiw,
--
Olly
Oliver Stephenson

electroluminescent wire...

add sound control and put it around the outside of the gauge, behind the chrome ring for some bling bling in your B, looks great and is invisible when not activated.

I know, not really the type of stuff to add to your classic, but I do sometimes get bored with the king of darkness.

Jochen
Jochen Beyer

I am not sure LEDs would work since they have a narrow angle that the light comes from them when compared to bulbs. As previously noted the gauges rely on a lot of reflection from the inside of the gauges to work. Haven't tried it though to be sure.

Simon
Simon Jansen

An electronics engineer I know used LEDs in a ring on his 65 Roadster and these are not visible at all, hidden behind the chrome bezel, and they really do improve his lighting. I will email him and ask him to post on here.
Martin
Martin ZT

An unexpected bonus when installing relays to power my headlamps was that the dash lights brightened all on their own. My uneducated guess was that by taking the headlamp load out of the lighting part of the harness, somehow it then allowed more current to pass through the old harness run to all the remaining loads along it, including the dash lamps, since those wires were no longer trying to also supply the headlamp filaments.

I am probably wrong about why, but for whatever reasons, the dash lights did brighten of their own accord, even tho NOTHING was touched in their local wiring, all relay related wiring having taken place at the front latch plate end of the headlamp harness. FWIW.
Bob Muenchausen

Bob , I would say you are spot on about the headlamp load , it was causing some volt drop to the point where the panel lights are split off.I shorted my rheostat years ago and find I can just live with the glow . White LEDs are an interesting idea , as they give more lumens per watt.
S Best

It is always fun to see how problems in one year car are handled differently in another. As Dave knows, Own a T series if you REALLY want bad instrument lighting. You either learn to see in the dark, have a flashlight handy, or use the engine sound as a guage for how fast you are going.

For the B. It is nice to know I have a few more options.
Bruce Cunha

I have a 67 Roadster too, same problem, the variety of solutions has given me food for thought. Ten years ago i bypassed the rheostat on a Mack truck i own...........no problems there at all!
E.L. Martin

Illumination?! You mean there are dash lights?? :)

Roger
'69 Roadster
Roger Hotelling

Had the same "dim" dash light problem on my 80 MGB. It was so bad that the gauges were almost unreadable. The ignition light also glowed slightly at all rpm. Replaced the alternator and solved both problems. The dash lights are now (very) bright and the gauges are easy to read.
Chuck Hassler

Just got back to reading this thread again.
Dan - I am against by passing the dimmer rheostat because, if the inside of the instrument cans are cleaned and repainted if necessary, the old, blackened bulbs replaced, the rheostat is cleaned up and all of the unintended voltage drops in the system are eliminated, the isntrument lighting will be bright enough to need a bit of dimming. It certainly is in our MGB.

Bruce - Ours is a late TD with two bulbs per speedo and tach and those, along with the oil pressure/water temp gauge can be seen quite well at night (I don't know if I have the dimmer turned down or not. The only instrument I can't see well is the ammeter and that is because I have not taken the time to replace the blue filter some one in the past stuck around it in place of the green filter of the proper density.
Cheers - Dave
David DuBois

Bob,

I have been toying with the idea of a headlight relay for years. Thanks for posting the comment about the added benefit of brighter intstrument lighting. I also agree with your premise that more current (power) is available for running the instrument lights.

I'll bet also that you're getting increased longevity out of that chinky headlight switch. On a '73, this switch is very cheaply made and all of the current to run the headlights passes through it.

Did you use an aftermarket relay? Where did you get it?
Richard Smith

This thread was discussed between 18/03/2005 and 05/04/2005

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