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MG Midget and Sprite Technical - Headlights

My headlights work but sometimes when I put main beam on the headlights go off.
Have got halogen bulbs and relays fitted.
What is the most likely candidate for causing this, light switch, relay of dip switch?
Incidentally my dip switch doesn’t look like any I can see in supplier catalogues, attached is a picture - any idea what it’s off?


Les Robinson

Could be anything.

You'd need to check voltages with a meter or test lamp when the fault occurs.

Is this any good?

https://www.ebay.co.uk/itm/326044299400
Dave O'Neill 2

Looks a bit like a mini dip switch, or an Austin 1100 one.
GuyW

Les
Assuming dip beam stays on then the switch is unlikely. So you have an intermittent connection somewhere, so check starting at the dip switch main beam relay feed followed by all connections to the main beam relay then any further connections between relay and main beam bulb connection.
Bill B

Assuming you have the original bullets connectors my guess would be one behind the grill needs a clean.

Trev
T Mason

Right then, had a good look at all connections and they are fine.
I reckon it’s the dip switch, if I put main beam on nothing happens but if keep lightly tapping it then beam comes on. If switch beam off then sometimes headlights weren’t on so lightly tapping the dip switch again made them come on.
Or could it be the relays?
Might try a new dip switch first.
Les Robinson

Since it's the wrong dip switch anyway, you may as well look for a correct one.
GuyW

Les
If you can get hold of an original correct dip switch, they're tough as old boots and re-buildable (and better than new aftermarket stuff). I rebuilt mine, including making a new threaded terminal and it's worked well since fitting.
Bill B

Bill
Funnily enough I have an old switch, think it came off a ‘65 Sprite although not certain. Anyway tested it and didn’t work so stripped it and cleaned the contacts inside and it works fine now so thought ah ha I can use this.
Then tested my existing switch and that also works fine.
So my conclusion is that it’s a relay issue.
Attached is a picture of the old switch I have.



Les Robinson

If you have relays in your lighting circuits, can you swap them around and see if the fault follows them?
GuyW

Actually, is it normal on Spridgety things for both main and dipped beam to be on at the same time? I am pretty sure on mine its an either or arrangement. The reason I know this is that on occasions there is an appreciable delay on the headlights coming on when I cancel the main beam. It seems like an age when suddenly driving in darkness but in reality its probably a fraction of a second. Still, for that moment oncoming traffic (the reason for dipping) must wonder where I have gone!
GuyW

The dip switch feeds power to either the headlights or main beam, not both.
Les Robinson

Try swapping relays, as Guy suggests. Or you may have an intermittent bullet connector, even though it might feel tight.
Bill B

Although it is legal for dipped beams to remain on when main is selected.

With relays, a decent alternator and appropriately sized power cables it could be a good idea to wire this way if you enjoy driving unlit roads at night.
AdrianR

Might the momentary black out when dipping that I get be due to the filament bulbs taking time to warm up? It does seem quite long though, like a slow blink. Long enough for an adrenaline reaction if its unexpected. Which of itself is interesting as a measure of how rapidly one's chemical & nervous systems respond.

I don't drive at night that often these days (contradiction there) but it may be worth rewiring to use both high and dipped together. Some of my most memorable drives in the outdoorsprite have been long night drives on fast open roads in the north country, with no other traffic, top down, dashboard lights off. Just the wind, exhaust and intake roar.
GuyW

Have fitted a new relay to the main beam and it works fine now. Hopefully that’s it all sorted.
Les Robinson

A bit late now, but one way of testing the switch would be to swap the two outputs with each other. If the fault stays with main beam, it’s not the switch.
Dave O'Neill 2

Fiddling about with the switch is a right pain due to its location. Even using it with your foot isn’t easy, there just isn’t much space being squeezed in between the clutch pedal and side wall.
So was thinking maybe fit a dash mounted switch, or one just under the bottom edge of the dash -(to save drilling holes in the dash). Will have a look at what options there are, any suggestions would be welcome.
Les
Les Robinson

If you aren't fussy about originality, how about fitting a later style steering wheel stalk switch. Gives main and dipped beam, headlight flash and indicators.
GuyW

And includes a horn push too doesn't it?

But somewhere in my head says the later combined stalk switch isn't an easy fit to the eearlier column. Not impossible, but a 'task'. I seem to remember considering it myself a while back... ; or was that my Capri?

Useful swap if it can be done 'easily' though. Use the horn push as a finger tip momentary wiper switch. Which is primarily why I thought about it.

But I much prefer the dip/main on the floor, so the dip/main on the stalk could control two speed wipers.

anamnesis

Yes, horn too. I forget about that. I have hardly ever used the horn on any car. I just forget it exists, at least until well after whatever might have necessitated it!
GuyW

This is what I have on my frogeye fitted by a PO, any idea what they're off? Someone suggested a Hillman Imp. IIRC right stalk is indicators, left stalk is high beam low beam when up/down and horn when pulled. I like them so they'll stay.

David Billington

Our first family car was one of the very first Morris mini travellers off the assembly line. 1960 "Little Jo" LJO can't remember the numbers though. My job, as front seat passenger, was to operate the floor mounted dip switch. That and to check oil, water, tyres etc every week. I can still feel that double click of the floor button.
GuyW

Yep David, Hillman (L)Imp; as it was unfairly in my view, called.

From the Imp owner's handbook.

"COMBINED DIP AND HEAD LAMP FLASHER SWITCH This is a 3-position switch. When the switch lever is in the central position the headlamp beams are dipped. Movement of the lever upwards switches on the headlamp main beams. Flashing of the beams is achieved by moving the lever downwards from the central position until pressure on the lever is released, whereupon the beams will be extinguished.

DIRECTION INDICATORS AND HORN SWITCH Flashing type self-cancelling indicators are fitted and will only operate when the ignition is switched on. The switch lever is moved upwards or downwards to obtain left or right hand turn signals, respectively, or pulled towards the steering wheel to operate the horn."


Looks really good. They suit the frog dash perfectly I reckon. Definitely keepers irrespective of anyone's opinion.

I'd bet you'd struggle to replace them if broken. Teeth, hen's, rare -- very.


anamnesis

Guy
I thought of your headlight dipping delay issue the other night whilst using the headlights on the Frog. Mine has relays too but the switchover from main to dip and vice versa is virtually instant so I don't know why yours isn't. You wouldn't think it was a poor connection as that would likely cause an intermittent fault.
Bill B

Maybe it's down to the internals of the switch and the point at which one light is energised and the other de-energised. Are the switches the same or different.
David Billington

Thanks Bill. Its not on the frog, it's the other one. I suspect a sluggish relay. I need to try swapping components around sometime. With long days at the moment and it never getting really dark, the problem is somewhat on the back burner for now.
GuyW

David B has nailed it I reckon.
Some relays (and some mechanical changeover switches) are "make before break" and some are otherwise. This is by design.
The test is to observe the lights changing from high beam to low beam and vice versa while standing in front of the car and having your glamorous assistant operate the dipswitch. If the high beam illuminates momentarily before the low beam goes out (or vicky-verky) you have make before break relays. These are common in moderns.
It's not as black and white as that though. Some switches are simply faster. In the case of relays that would indicate a stronger primary coil than otherwise. For mechanical switches it would suggest a stronger trip spring.
Greybeard

David/Grey
Yes, sounds like you're both correct. Perhaps the column dip switch, presumably present on Guy's later Sprite, is "slower" than the foot operated Frogeye dipswitch. I'd have thought the relays were fast enough (one relay for main and another for dip beam) so maybe less likely to cause the problem.
Bill B

Thanks for correcting me Bill. For some reason I had fixated on the idea of a modern type two-way changeover relay instead of the much simpler solution of a pair of single throw devices. Even though that's what I installed in my 1500, and several other cars.
I suspect you're right about Guy's stalk switch. They are mostly make-before-break I think, but if so it's possible that the contacts are a bit compromised by years of carrying the full lighting current before the relays came along.
Perhaps a good blast with contact cleaner would make a difference?
Incidentally the late type combi switchset with high/low beam, turn signals, horn push and headlight flash is pretty hard to find. I had a spare but I passed it on to a BBSer years ago.
The simpler type with just signals and high/low beams seems easier to track down.
Dunno why.
PS; I like David's Imp switches. I'd forgotten all about them.
Greybeard

This thread was discussed between 04/06/2025 and 14/06/2025

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