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MG MGB Technical - Dash Lights

Last weekend we were driving our '72 B well after dark (which we rarely have done) and noticed it had dim lights. I was able to adjust the rheostat to get it the "brightest" but it was still difficult to see. Each instrument or gauge had some illumination, just not much. Any one have any ideads of how many bulbs are in each instrument/gauge, and are they the threaded or the "eared' base. I plan to crawl under the dash this weekend, but would like to have the right bulbs on hand to replace if necessary.
Joe

Yep mine are very dim too. This has come up before, you may want to check archives. From what I can remember not many elegant solutions were offered. One is to just hardwire past the rheostat, this removes some resistance and will give you the max juice to the bulb. I've been curious about also adding a brighter bulb, it may burn out sooner but if I have to replace even once a year it's a small price to pay for nicer brighter lights. Perhaps someone will offer a better solution or know of a replacement bulb. Could also go out and by some night vision glasses from your friendly special forces soldier or by a mining helmit with brim mounted light. I also wear a light that clips on the brim of my hat for fly fishing in dim light....but now I'm getting off topic.
Brian

You might want to check out that rheostat...I had the same problem on my 67 MGB. I jumper'd over it and the bulbs shined bright. I just leave the rheostat switch in the dash for looks, but I left it bypassed for the maximum illumination. The bulbs are the threaded type. -Rod
Rod in NC

Numerous things affects how bright the lights show up on the instruments. Of course, the rheostat is the first thing to take care of. Pull it out of the dash and clean it well with some contact cleaner that can be purchased from Radio Shack. When this is done. then turning the rheostat all the way to one side or the other (can't remember which way removes all the resistance and essentially jumps the rheostat out of the circuit. Check that the ground circuit for the lights has a good connection. The connection should be to a spot on the body that has been cleaned to bright metal and preferably coated with something like Kopr-Shield, a conductive, anti-corrosion surface compound made by Thomas & Betts (P/N 201-31879) to improve the conductivity of the connection and prevent corrosion. Finally, insure that the blue colored film in each instrument is clean and not fogged from old age. Good luck - Dave
David DuBois

Every one I've ever met who has ever owned an MG complains about the dim dash lights, I, like Rod, eventualy bypassed/shorted the rheostat. The cause might be age and tarnish as Dave says or the lights may have been like that to start with, you never know with MG's (any one out there had one from new and can tell us?)I've thought that a possibility might be to replace all the bulbs with a lower wattage variety. Before you switch on the lights for a test (if you try this), turn the rheostat to max' resistance/dimness otherwise you might blow all the bulbs and have to start over .
Peter

I forget where I saw this but Radio Shack has bulbs --their # 55 that fit the instruments on MGBs they are 7.5 v so burn brighter in 12v system. I have converted all my instrument lights---with some effort-- to these and it is an improvement . To lenghten bulb life just turn down reostat a little ---worked or me !
Gil Price

Get some halogen bulbs. They are a bit pricey, but well worth it, as they make a big difference. My gauges were just about unreadable at night before I put the halogens in. Now they look great. (In fact, I've got a 66B without dash liners, and the light from the gauges is so bright my feet are illuminated as I drive at night...)

I bought my halogens from Little British Car Co. www.LBCarCo.com
They can tell you which bulbs you need.
Kim de Bourbon

I have a 68 GT and for me, I found that installing relays, as Dave has mentioned, automatically rerouted the electron flow and without any other changes, my dash lights came up to a very nice level. 68's don't have a dimmer switch to bypass, but apparently there were enough losses within the OE wiring harness (for whatever reasons) that simply moving the load from the headlamps out of the OE wiring path, was enough to allow the dash lamps to brighten.

I think you could compare the OE routing's problem to that of your own household wiring, both of which send current over branches (circuits) from their source (battery/alternator for the MG, Mains for the house). Ever notice that sometimes when a large load device cycles ON, like a refrigerator compressor, the lamps in the house temporarily dim? Yet, if you were to give the fridge its own circuit, the lamps that remained on the original circuit tend to dim less or not at all when the load strikes.

I think this is what happens within the B harness in its original form, and adding relays to the headlamp circuit is comparable to adding a separate circuit for them. A long way around to getting brighter dash lamps, I'll admit, but if it presents a better balance of current flow through out the system, so much the better. And using relays has the additional benefit of presenting far less load to lighting switch contacts, allowing them to last much longer.

The best sites for relay conversions/install info, are http://www.mgbexperience.com/electrical/relays.html and http://lighting.mbz.org/tech/how_to/relays/ - Good Luck!
Bob Muenchausen

Jim,

One factor which affects instrument lighting brilliance (or dimness) is the extent of reflection inside the instrument casing. You can remove the instrument, take off the bezel (by rotating until the clips release the front - or, if the instrument is old and slightly corroded, slightly bend back the clips - remove the instrument from the casing and repaint the inside of the casing white or silver. As in the Havnes manual, re-assembly is the reverse of the disassembly process! It might be worth putting a new rubber seal behind the glass - perhaps a suitable rubber band would suffice.

The other thing is to clean the glass and the bulb and to ensure you've got a good earth. (How often does the term 'ensure you've got a good earth come up!?')
Peter Hills

Bob - Good analogy, bad example. I don't know about the wilds of Idaho, but in most of the rest of the country, the cods require a seperate dedicated circuit for the frige : ). Cheers - Dave
David DuBois

Just my two cents worth...I too bypassed the rheostat on my '64 B. The tach and speedo lights did get brighter. I can't say I've noticed a big change in the fuel gauge or oil/temp.

In reply to Gil's suggestion, I used the 7.5v Radio Shack bulbs in the tach and speedo. They were brighter than the stock, and did last 2-3 years. But they both burned out with a day of each other. That is when I bypassed the rheostat. I would say that the bypassed rheostat with the correct bulbs gived about the same brightness as the 7.5v bulbs.

But, the gauges still are no where near as bright as modern car gauges. I'll be trying Bob's suggestion of the relays for the headlights.

Bill Barge

This thread was discussed between 29/05/2002 and 30/05/2002

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