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MG MGB Technical - Instrument bulb

Might anyone know the correct bulb number/style for the tachometer on a '74 mbg?....Thx
Pete

Same as the speedo? You would need to look at the socket first, they are usually screw in like a torch/flashlamp bulb but could be bayonet or even push-in. Other than that they are 12v 2.2w.
Paul Hunt

I found it...on this side of the Atlantic...GE 1449, screw in base...
Pete

As an aside on this thread, Ive been meaning to ask. Is there 2 bulbs or just one in the speedometer? Its just that half of my gauge face is dark and the other half is fine.
Ross Kelly

Only one in each of the gauges. Maybe the bulb is wearing out and silvered on one side, there shouldn't really be anything else capable of screening it off.
Paul Hunt

It also may not be fully pushed in to the tube on the speedo.
Paul Hunt

Wow!...I recommend changing old bulbs...Its like a new dashpanel...but oh, that speedo bulb is tuff to get at!...
Pete

was recently a passenger in an MGB where the instrument bulbs had been removed and replaced with LED 'bulbs' - basically little LED units in a capsule which was a straight swap for the original bulb. These were blue in colour, and gave out a lot more light than the traditional bulbs. Being half-cut at the time, I forgot to ask where these were purchased from - anyone else used them, and if so, can you detail where you purchased them from?
Thank You
Mick
mick

Mick,
Try www.ultraleds.co.uk. I seem to remember they do a large range of auto leds and you can also buy dimmer controls for them.
Regards
Richard
PS If you're sucessful let us all know. I'm some way from re-fitting my dash but instrument lighting is at the top of my list of improvements!
Richard Coombs

Ultraleds indeed. However they do render the factory dimmer inoperative and I'm not aware of an alternative from Ultraleds. I tried some white ones and although they give a better light in the speedo and tach they were not that much better, and the smaller gauges were virtually no different, see http://www.mgb-stuff.org.uk/wn_electricsframe.htm, click on 'Lighting', 'Instrument Lighting' and 'Uprating'.
Paul Hunt

Another site which does offer dimmers is www.led1.de. Their dimmer is an Osram part so you may be able to get it elsewhere.
If you are even more practical have a look at the circuit shown on

www.reuk.co.uk/240V-LED-Bulbs-and-Dimmer-Switches.htm.

Pulse Width Modulation (PWM) is the way to go but I suspect the control needs to be somewhat non-linear because of the led and the eye. Probably not a real issue for car dash illumination.
Richard Coombs

Imagine! Need for a dash-lamp dimmer control... I took mine out in favor of an intermittent windscreen wiper control. I have had halogen instrument lamps for many years. Even so, I can't imagine any need for a dimmer pot. The lamps are just the right brightness for all gauges - large and small. No they don't get too hot; and on three different cars I've never had one burn out. Yes they probably would burn out the dimmer pot, but that's academic.

FWIW,
Allen
Allen Bachelder

I agree, the provision of dimmer control for the standard bulbs is somewhat of a joke. But if you uprate the lighting you may find you do need it. I once hired a car for a night journey and found the instruments so bright on unlit roads I couldn't see where I was going. Couldn't find a dimmer, so had to put the hire documents over the instruments. Couldn't see the speed, but at least I could see the road.

In the UK we have Smartscreen (http://www.smart-screen.co.uk/) which uses the existing wiper switch to vary the sweep time between 3 and 30 secs. I have them on both my MGBs and find I rarely need continuous wipe.

Paul Hunt

Hello group,
I would like to replace all of the light bulbs in my dash as they are all very dim. Is there a place I can find or does someone have the bulb part #'s for the halogen replacements? Do I need to replace the toggle swithces as well or just bulbs inside. I have a 74 MGB GT built in Feb. 1974. No rubber bumpers..

Thank You,
Gary Odum CPS
Grapevine, TX
G W Odum

LBCarco sell halogen replacements for MGB instrument bulbs, but they are very expensive and you need to select the right wattage for your year or the much higher heat levels of halogen can damage the gauge.

MGB dash lights are always dim, especially by today's standards. First check the bulbs are clean, aren't silvered inside (in which case standard bulbs may bring a good enough improvement), clean the inside of the glass, paint the inside of the cans, and finally try bypassing the rheostat. Printed-circuit versions of these at least have a failure mode whereby they make the lights dim even on the brightest setting. Replacement rheostats are very expensive for all the use they are, so just bypassing may be enough.

Finally drive your car more, the beauty of analogue instruments as that you only have to see the angle of the needle, not be able to read the number they are pointing at. How many clocks and watches these days don't have numbers on the dial?
Paul Hunt

If you go to LBCarCo.com, hit "search" and type "halogen" into the search window. The halogens share the same Moss numbers as their tungsten brethren, with the important difference that the numbers are suffixed with an "H". LBCarCo makes it clear in the descriptions that the 5-watt bulbs are for the small gauges (fuel, oil pressure, and temperature) whereas the 10-watt bulbs are for single-bulb large gauges (tach, speedo). All of ours are single-bulb.

After they've been on for awhile, if you put your finger on the glass of the small gauges you may think they're too hot, but they're not. I've used these bulbs for many years with no problems. Heck, in the winter time, enjoy whatever heat you can get! The difference in illumination is nothing short of fantastic. Nevertheless, you don't need a dimmer!

BTW, as a retired music theory teacher, I can precisely determine the speed of my MG at night without seeing the speedometer. It requires basic knowledge of musical intervals and a pitchfork. If you want to find out how, e-mail me. It's a long-winded explanation and I don't want to bore the list with it.

FWIW,
Allen
Allen Bachelder

Forgot to ask - Paul, several years ago I tried to order an intermittent wiper switch from Smartscreen. They acknowledged but never delivered, so about a year later I ordered one from Moss. I thought I was getting the same thing but apparently not. I'm very happy with the control I have but one working from the original stalk switch would be a lot neater.

I had concluded that the company had gone belly-up, but are they still alive and kicking?

Thanks,
Allen
Allen Bachelder

I reference them on my web site and at one time had a comment that they seemed to have gone AWOL. The owner of the company must have seen it as some time later he contacted me to say they were now back in production after a problem getting parts. Moss (UK) still show the proper Smartscreen, whether that means they *are* available again or they are still showing the 'old' item I don't know.

As you say working from the original switch is neater than having an additional switch, but it does catch me out every now and again by my getting out of sync with what the unit is doing, and thinking I am giving it two pulses withe appropriate delay between them, whereas at my first pulse it is already in a delay so it stops it, and my second pulse starts another 'learning' period! You can avoid that if you have the LED visible, but I have mine tucked up behind the dash. Nevertheless intermittent wipers are extremely useful, I have them on intermittent much more then I do full-time. Ironically my 89 Celica only had 3 switchable settings instead of the continuously variable of the Smartscreen, and my 2004 ZS only has a single intermittent delay! Sort of off, flicker and on ...
Paul Hunt

Well, rebuilding the tach and speedo cans, reflective white paint and a second LED 270* ultrabright from LEDbulb.com about 180 opposite the stock one, has really enhanced brightness on the 76-80 dash and I went to blue light color-much softer to me at night. The clock, oil, and water temp all were changed out to the one LED in blue. Not blazing bright and I am considering one more,blue, but lesser wattage LED with same 270* spread. Speedo/tach glass is being gang purchased by L. Ingram, on this BBS, for $5 each...a necessity on the rebuild. Cheers Vic
vem myers

The Smartscreen is also available with a sounder function so that it will bleep to tell you whether your "input" is the first or second of the delay period.
Jonathan Stafford-Mills

Haven't heard of that feature before and it isn't mentioned on the suppliers web site. There is a wash-wipe version if you have electric washers.
Paul Hunt

Paul- Have you seen the v-drop through the dash mounted dimmer switch ( rheostat)?
B+ comes in about 12 volts, but resistence throught the dimmer, drops 2-3 volts outgoing when measured. Heck, we're all half geezers and use full on dimmer. I've just bypassed by ganging and soldering the r/w lighting wires. I put the choke pull in the old dimmer hole and sell the dimmer on E-bay for $20 or more. Vem
vem myers

If the dimmer is faulty it drops voltage, it shouldn't drop any on its 'maximum brightness' position. This has been the failure mode on every rheostat I have had, which have all been printed-circuit type and not wire-wound. The printed-circuit type have two parallel paths for current, but when the high-current path burns out you are left with the low current path only, which gives you variable brightness as before, but less maximum brightness. Replacing the rheostat restores full (a relative term) brightness. Yes, they are expensive, and I have never used them on anything but maximum brightness, but I hate things that don't work.
Paul Hunt

This thread was discussed between 12/08/2008 and 14/09/2008

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