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MG MGB Technical - Headlights

I need to do something about my headlights.

At the moment I've got H4 Autopals with 100w/80w halogen bulbs. Main beam seems a bit high and fairly dim and dipped beam is slightly better, but still yellowy, and is a bit low. Seem pretty bright when looking from outside of car.

My first thought was I wasn't getting the required volts, but I seem to be getting 12.6v with a 0.5v drop. Anyway, I've now fitted relays which didn't seem to make much difference. All other bulbs are standard and I've a Lucas 18ACR alternator fitted.

I suspect it's the reflectors, rather than the bulbs, causing the issues.

In days of yore I had Lucas sealed beam units which I remember as being OK, but maybe my eyes aren't quite what they were, or I've been spoilt driving my wife's Golf.

Any thoughts on the above, or recommendations on decent headlight units?
Peter Allen

Well you have removed the switch and some bullets as possible resistances. But the main connection culprits are the forward ones under the slam panel. They are the ones which get the most weather thrown at them and are most likely corroded. Clean or replace them all, and make sure the headlamp ground/earth is good.
Those 100/80 bulbs are technically illegal, for off-road only. Everything being electrically good, you lighting should be stripping paint off the car in front!!😎
Allan Reeling

What make are the bulbs? There are some absolute rubbish 'hi wattage' bulbs.
I know I fitted some, first time out I had to stop to replace them with the old 55 watt so I could see to get home.

Relays will help with the voltage drop, but you will need thicker wires from the relays to the lights, cannot remember what size wire.

And, yes 100 watt bulbs are illegal on the road.

Colin
Colin Parkinson

Thanks for the input, chaps.

I cleaned up the connections under the slam panel as part of the relay installation. Original gauge wires from lights to relays (located just behind slam panel). Both lights put out equal light. Apologies - when I said dim. It's not like a bad earth/ground dim. They seem bright enough from outside, and as said, have good volts.

Can't remember what make the bulbs were, but initially I might go back to the 65w bulbs I had before. If that doesn't work it may point to the reflectors. I'll then try the old Lucas sealed beams out of my Riley.

I was hoping that somebody would say that the recipe for half decent headlights in an MGB, once you've got past good maintenance, is, for example, such and such reflectors with such and such bulbs.

Point noted on illegality of bulbs!
Peter Allen

Assuming you have 100w mains the fact they seem dimmer than dipped does tend to indicate there are volt-drops somewhere as they take 25% more current.

Where did you measure the voltage? It has to be as close to the bulb as possible or you are not seeing the effect of any volt-drops further on.

Did you measure the volt-drop in the earth wires? Depending on the year this often comes back to a body earthing point near the fusebox and relay(s). Again this has to be done from as close to the bulb-holder as you can get (easier than the live side) to a good body earth elsewhere.

Problems are usually in switches and connectors not wiring - factory wiring at least which on my 73 and 75 is a thicker gauge than most other wires. Relays get over most of that but still leaves the connectors under the slam-panel as said and earth wiring.

Reflectors are an unlikely cause unless they are visibly discoloured with the lights off.

Relays should make a big difference to losses in the supply side. I fitted some for a pal with 100/80s, he said before that when switching from main to dip the 'new' beam came up with a noticeable delay, after it was instantaneous and noticeably brighter.

With relays fusing should be considered or any shorts can damage wiring more and faster than without relays. At least one fuse per beam, if not one per filament or you can lose the headlights completely.

paulh4

I was going to recommend the Cibie / Valeo 7" headlight, but it seems they are no longer available, or at least I can't find anyone with stock. I have these on my GT and they are excellent with standard H4 bulbs (not those over-powered ones you have), better light than my modern VW. The Cibies have been on my car for over 11 years and show no sign of deterioration.

I have Autopal headlights on my Dolomite and they are rubbish. Made in India they have poor beam control and are not a patch on the real thing.

Since Cibie/Valeo aren't possible, another decent make is Hella and you can get these from Demon Tweeks https://www.demon-tweeks.com/uk/hella-7-inch-e-approved-headlight-conversion-hel1l6002395-261/ Depending on the age of your car you may not need the sidelight facility, so just leave that bulb out.
Mike Howlett

Peter , now that you've fitted relays, it's an easy little job to link Hi beam into your Lo beam relay so that you have both beams going on Hi
Good trick to get more light on the road on Hi beam
Have you checked your headlight beam adjustment--It sounds a bit weird that Hi is too high and Lo too low --- dodgey globes are the most likely cause of that.
MkV VW Golfs had a similar issue where the (separate) lenses in the headlights weren't matched Hi up in the trees and Lo pointing at the ground, If you set say Hi correctly Lo would point at the ground but if Lo was set correctly Hi would be up in the trees--A cheapy pair of aftermarket headlights was the fix for them, the genuine reflectors were just junk

willy
William Revit

Peter, Mike and Willi have hit the nail on the head; Focus is the key to sharper lighting, we can change the colour temperature with new bulbs to get a whiter light or increase the wattage to get more light but in either case, the effect is wasted if the light is not accurately focused.

The debate predates the H4 conversion when the factory headlights were not up to the improved performance provided by the B. Spot lamps or a spot/fog combination was essential. Dealers fitted Lucas versions but in the early sixties the word went round that Cibie lights were sharper and more useful. We changed ! In 1961 mine were on an A.

Since then the H4 conversion has made the B a reasonable proposition for nightime use. I came back to the B after a short spell with a P1800 fitted with Hella heads. Since then all our MGs sport Hella lights. The originality argument does not hold water with brakes or lights.The MGA also has an alternator.

It's a pity these issues get forgotten - we need a Barney Gaylord (MGAGuru) for the B. Doing anything Willi ?
Roger Walker

Thank you very much all for your very comprehensive advice and feedback.

Allan, Colin, Paul - I'll check again voltage at the headlights. It was 12.6v behind the bulb before I added the relays. I'll also check the earthing again. Think I'll back off on the wattage and return to more sensible (and legal) wattage bulbs.

Willy - yes, I had checked the adjustment. Doing the chalk mark test on the garage it looked about right. You and Mike have confirmed my suspicions that the Autopals might not be the best. You sometimes get what you pay for!

Thank you Mike & Roger for your recommendations for the Hella conversion. A bit odd that Valeo/Cibie seem to have dropped the 7" lights. Interesting that the lights weren't considered that good in the day - I guess back then they would have had BPF fittings.
Peter Allen

I fitted the Hella headlamps to my MGA a few years ago and they are really good.

Mind you, the old ones were brand-new repro Tripod units which I did like the look of, but the lens design was so bad that you could honestly not tell if you were on dip or main. When you hit the dipswitch, the beams just illuminated different sections of the the tree-tops!

I gave the Tripods to Frank Camilleri in Malta quite a few years ago as he was desperate for a set, he just paid me the postage. I did warn him though that they were pretty useless as lights.

But I think he may have binned them since then so I am glad I didn't actually charge him for the Tripods.

I have been recently looking for a set of Cibie/Valleo headlamps as the Hellas are showing signs of age, but so far, I have not been able to find any and I may have to get some more Hellas.

Cheers
Colyn
Colyn Firth

This thread was discussed between 08/12/2021 and 10/12/2021

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