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MG Midget and Sprite Technical - Intermittent light failure

Hi everyone, I don't doubt that the answer to this lies in the archives but I can't find it. Any wise words would perhaps save me some time searching the car's electrics tomorrow.

This evening I experienced several episodes of fortunately brief but pretty unpleasant total headlight failure , dip and beam, possibly sides too, they came back on before I killed myself.

Any thoughts regarding the most likely cause? I wondered about a dodgy common earth but a quick check isn't showing anything obvious. My next thought was the switch or feed to the switch? That seems odd given it was intermittent.

The car (the MkIV) is on halogens with relays on dip and beam which have been trouble free for about eight years now.

Intermittent faults are always trouble to find in my experience and I definitely want to find this one before it does it to me again, it was highly un-amusing.

Paul
P Simpson

" I wondered about a dodgy common earth but a quick check isn't showing anything obvious. My next thought was the switch or feed to the switch? That seems odd given it was intermittent"

There is a common earth at the bullet connector near the offside headlamp.

No reason that a faulty switch wouldn't be intermittent.

Do the relays share a common power feed?

Another possibility is the dip switch.

You might want to check for voltage drop across both the headlamp switch and dipswitch, possibly due to high resistance in the switches.
Dave O'Neill 2

Thanks Dave, that's useful and gives me a logical place to start the investigations. I think that the relays do share a common power feed.
I've never enjoyed electrics...
P Simpson

Paul-You could try the old wriggle test-
Turn the lights on, in the semi dark is probably better so you can see the light
Then go round and wriggle connectors etc-
If you have relays already ,the load has been taken off the switch(still a possibility) so I'd start with the feed to the relays and the earth to the lights-,-dipswitch-?
William Revit

Paul, I have had similar with my MK1V on more than one occasion. In my case it is as I go from dipped to main beam, the dipped go out but the main beams don't come on! Pretty unnerving on a dark country lane, and even more so if there is oncoming traffic and you know you have just become invisible!I

Mine also have relays, but with separate power feeds for the main and dipped relays. I think the fault is the contacts in the indicator stalk dip switch. In damp conditions they get a coating of moisture and possibly it's the copper contacts corroding slightly - enough to block current to the relay. After a (long!) moment it burns off and the connection is made so the lights come back on again.
GuyW

I'll put my money on the dip switch.
Jonathan Severn

The wonderful bullet connectors are my prime suspect. They are exposed to damp and muck behind the grille and gradually corrode inside until they can no longer pass the current. It should show up with Willy's wriggle test.

If you have relays, the current load on the dip switch is so tiny that I wouldn't class that as number one suspect.
Mike Howlett

I've found it (easier in the workshop than standing at the roadside in torrential rain and howling wind).
The culprit was the live feed to the relays.
Now that I'm enlightened as regards the absolute catastrophe potential I will be re-wiring to split the feed somehow so that a similar fault won't wipe out all the lights, I might take a look at the earths too.
Thanks for the advice.
P Simpson

Result.

I have yet to fit relays to my headlamps, but separate power feeds is something I will bear in mind when I do the wiring.
Dave O'Neill 2

Mike,
You are right about the low current through the relays. In my case, reducing the current load on the switches was the prime reason for fitting relays. But my interpretation is that in cold or damp conditions (and it was very "damp" here yesterday when Paul's lights failed!)the current through the button contacts in the switch is so low that it doesn't provide the heat to dry them out, and so they corrode or remain damp long enough to cause the temporary black-out.
GuyW

Yes, it was certainly damp, these things always seem to happen when it's damp. Not as damp as this time 4 years ago when the Sprite ended up in 3 feet of water at it's MOT.

All sorted now I hope, I've rewired the relays separately to live feeds, unfused, although I suppose if I fused them both separately the no lights risk would be low if a fuse blew.
New bullet on one earth just in case, as it looked a little shabby.

I got round to making a switch bezel tool too, after 35 years I've had enough of faffing about with circlip pliars.


P Simpson

I had an argument with the MGOC when I fitted their headlamp relay kit. The instructions called for one fuse for both the main and dipped lights. This I thought was crazy, as suddenly losing all lights on a country bend was not something I wanted to contemplate.
I split the power supply and fitted two fuses. They said this was illegal, as driving on full beam is not allowed.
My reasoning was that at least you could get to a safe spot to stop.
The original system did not have any fuses.
Dave Barrow

I'm not sure why they would think this is illegal.

Just looking at a Haynes manual for a Vauxhall Omega that I once owned. It shows four headlamp fuses - dip and main, both left and right.
Dave O'Neill 2

Dave
They said that driving on full beam would be illegal, in the event of a dipped beam failure.
I said that I was only talking about the minimum time to get to a safe place.
They said they could not endorse this modification in the kit.
So the kit still recommends one fuse for all main lights.
Dave Barrow

How can they say that driving on main beam is illegal in the event of dipped beam failure?
Driving a car without any running light failure might get you pulled up by the police, but I really don't see that means that having seperate fused cables for main and dipped relay supplies is illegal.

People drive on main beam all the time, and many seem loathe to switch down to dipped lights. Though I suppose it is unlikely this is because the dipped beams don't work!
GuyW

Dave B I had the same issue with the MGOC kit and opted for a similar solution to yours, except that I arranged the wiring such that if a relay failed I can quickly swap them. If high beam fails then I still have low beams to get home, but if low beam relay quits I can swap wires and carry on with the other relay.
The same redundancy applies to the lamp fuses.
It doesn't help if a lamp fails of course, but I have a spare set.
Edit: this was a lesson I learned the first time I drove the Midget when I lost high beams forty miles from home, which was why I fitted relays in the first place.
Greybeard

In my yoof i was told never have fuses in light circuits, but it seems normal nowadays

In the past I've always used circuit breakers like these-
The only problem with them is that they are a tiddle slow to reset-----

https://www.ebay.com.au/itm/30A-AMP-12V-Circuit-Breaker-Cover-Dual-Battery-Fuse-Automatic-Auto-Reset/302177100223?epid=22020307837&hash=item465b28a1bf:g:K-kAAOSwux5YYLCx

But now there are some nice little circuit breakers (faster reset) that push in instead of blade fuses like these, If there is a short in the lighting they just flash instead of loosing lights altogether like with a blown fuse-- but be aware there are two types auto or manual reset---auto reset is the one needed

https://picclick.co.uk/1pcs-Automatic-Resettable-Fuse-Auto-Marine-Circuit-Breaker-192167074358.html

If you haven't got a fuse block suitable to push them in you can wire direct onto them with normal crimp on terminals or get an inline holder like this/these---but the little cap won't close over the c/b

https://www.ebay.com.au/itm/12V-In-Line-Standard-Blade-Fuse-Holder-6-Fuse-5-10-15-20-25-30A-Automotive-Car/362486510018?hash=item5465e131c2:g:fRkAAOSwa81ZdxQP
William Revit

Dave,
be fair you they can't say (if it is against the law, I don't know not looked it up) it OK to break the law for a short distance. There are a few strange legacy regulations about car lights going back to the days of "us making our own laws for ourselves".

Like David though I remember at least one (70s) Fiat with fuses that acted on one side of one or some of the car lights.

I think headlight relays introduce unnecessary complications on a Spridget with good wiring, switches and connections, unless you need/want to keep some old original switches going and enjoy a bay full of wiring and possibly carrying addition spare parts like relays then you can get away with very good and reliable headlights. The cars didn't originally have fuses or relays on the headlights and were fine for very many decades, I think this Prince of Darkness is wrong too considering 50+ year old cars still have original equipment in use.

And I've had trouble with one of the only two relays fitted to my Midget ("awl no, you never get problems with relays ... very rare ... oh I think it might be the relay").

Guy - my modern stalk switch is/was(?) still working without the benefit of relays - but putting that has put the kiss of death on it now. :)


Nigel Atkins

I have the solution - don't go out at night ;-). Or use the modern - I have never had both headlights fail in almost 50 years of driving.
Bill Bretherton

Nigel said "The cars didn't originally have fuses or relays on the headlights and were fine for very many decades,"

Correct Nigel, but after 50 years of switching quite high current loads the contacts on the switches will have deteriorated. Putting relays in the circuit should protect the switch so it can last a few decades more. We are always beefing about how poor modern replacement parts are, so it makes sense to preserve the originals.

On some cars like my Triumph Dolomite the rotary light switch is just about irreplaceable, so unless you want to fit some alternative and spoil the interior of the car, relays seem only sensible.
Mike Howlett

Most of my driving is in the dark at this time of year, I fitted the relays as I was onto my last dipswitch/stalk and wanted to try and preserve it.
To be fair it wasn't a relay that caused the problems.
I hadn't had both lights fail in 35 years of Sprite driving, once was enough.
P Simpson

Has anyone considered LEDs? Such as these from Classic Car LEDs

http://www.classiccarleds.co.uk/collections/headlight-led-bulbs/products/latest-led-headlights-h4-philips-z-es-hi-lo-beam-conversion-9-32v

A more expensive alternative admittedly but with the advantage of improved lighting and less current being drawn than with halogens (without relays).
Jeremy MkIII

The Jury's still out on LED headlights as far as I'm concerned, Brighter, lighter to look at yes but I don't think they penetrate as well as normal globes and then you get everyone flashing their lights at you thinking you're on high beam when you're on low and, when it's raining fairly solidly the light reflects terribly off the rain limiting vision---when you need it most
I took mine out and went back to normal 130W globes and am happy with that
Personal opinion though
willy
William Revit

It is a minefield, but from what I can find on the web, putting LED bulbs in a lamp designed for a tungsten or halogen bulb is not legal in the UK. That's not because they are badly designed, but simply because there has been no testing and no legislation since 1986.

Current vehicles have lamps with reflectors and lenses designed to be used with LED bulbs and so those can be "E" marked. Our old cars have lamps designed to use a hot wire bulb that has a very compact source of light, and the reflector and the lens were made to use that type of source. Any replacement LED bulb will have several light sources spread over a larger area than the unit was designed to accept. Thus it cannot be "E" marked and so is technically illegal.

That's not to say they will fail an MOT or roadside check (unless they actually dazzle on dipped beam or are too blue in colour), but if the tester or police officer wants to be pedantic, they can fail you for having them.

That will remain the case until government agencies test the new bulbs in all types of lamps and the legislation is rewritten. Don't hold your breath waiting.
Mike Howlett

Mike, that is my understanding too. Modern LED headlights have a very precise cut-off of the light which is necessary because of the light intensity, presumably. An older reflector would not provide such a cut-off.

Willie, interesting what you say about LED light in rain. I find it difficult seeing well in the rain on poorly lit roads with defective cats eyes (common here now) in our modern LED equipped car. I thought it was me getting older! Well I suppose that's a factor, inevitably, but if what you say is true then that makes a lot of sense.
Bill Bretherton

As well as light reflecting off the rain, I find the ultra-reflective road signs now in use can be quite dazzling too.
Mike Howlett

"LED headlights have a very precise cut-off of the light which is necessary because of the light intensity"

The practical problem with this is that there are many drivers who either don't dip, or fail to appreciate how far the intense main beam throws and delay their use of the dip switch. Add to this that if you are on an undulating road, then even a dipped headlight will shine well above the designed cut-off level and it's no ones fault, other than those who sit at computer desks and designed the standards without appreciating the diverse real-world conditions.

I think there is a good case now for three settings of lights rather than just 2. There should be a lower intensity dip and main beam for normal driving conditions on busy roads including but not limited to urban areas. This would also reduce the excessive rear-view mirror dazzling that we are particularly prone to in our little cars. The third, high intensity lights should only operate on fast relatively empty roads when the longer view is actually beneficial. In reality, in the busier parts of the UK, such conditions are relatively rare in some parts of the country other than possibly in the early hours.
GuyW

The other thing with a lot of moderns is that they dip automatically and only in the area where they think something is rather than completely.

As for dazzling I find following an ambulance to be bad at night. I cant understand why they dont have switchable lights like police cars so that the rears dont work when travelling.

Trev
T Mason

Since I'm about to replace the 60 year old wiring in my Frog, I've been considering also going to LED headlights "while I'm at it". I've gotten a relay kit and a new harness but now I'm debating whether I should go with the LEDs or stick with the originals. You all are making life difficult ;-D
Martin

Martin, you will need to find out what the regulations are (if any) in your state.
Mike Howlett

Martin,

me too. Our cars were small (and low) when they were new and are positively tiny compared to the giant SUVs everyone seems to want to run so anything which makes our little cars more visible is to be welcomed IMO. To that end Santa is bringing LED stop/tail lights and four indicator bulbs (with electronic flasher) from the above site.
They look a really nice piece of kit as the body of the LED is made from aluminium, what they're like in practice will have to wait until the 25th.
If they make a significant difference then headlights may be next on the list, along with warmish white sidelights.
Jeremy MkIII

I went all LED (except IGN light) years ago and have never regretted it. The LED bulbs have to have the LED centre line and position the same as the halogen bulbs. After that all the cutoff pattern is dictated by the lens. The classiccarled guy has always sold me good H4 units ( I have done the conversion for a few others too). No relays are then needed

The lights are fused (have had one loom burn out because the license plate lamp was poorly connected after a rear-ender and fell out to cause a short). I'd rather have the fuse blow than have to replace a loom.
Dominic Clancy

Mike,
I take your point of having lots of extra wires, connections and relays if you need/want to preserve original switches but as I put for Guy my last purchase of modern made column stalk is still working well and without any problems so it is possible that when even the tight-fisted classic owners get fed up, or discovered, how poorly made some parts were even they insisted on better made parts.
Nigel Atkins

Jeremey,
you're best to use LEDs in full sets to the circuit so with your indicators you'll want to add the two tell-tale dash lights bulbs too and for your rear side (brake) lights you want to add the (warm white) front sidelight bulbs and rear number plate bulbs too. If you gave hazards then I think you'll need a second electronic flasher unit.

Bear in mind LEDs may show up any shortcomings in your existing wiring, earths and connections and mixing incandescent and LEDs in a circuit (or for comparison between the two types of bulbs) doesn't always work out well.

All the good quality LEDs (not counting headlights but see next) I've seen fitted to classic cars give much brighter and safer lighting, reduced loads on the battery and those switches and contacts.
Nigel Atkins

Only yesterday a mate who uses a Spridget as a daily told me he'd switched to LED headlight bulbs, the ones from the MGOC (other suppliers are available), to go in his existing H4 reflector/lens units and he said the LEDs were a great improvement.

LED headlights must now be on 6th or 7th generation of improvement so more recent are probably better than the earlier ones.

There were (still are?) some cheap poor quality LED bulbs of all types being sold and some good quality ones so you have to know which quality level anyone is reporting on.

Nigel Atkins

Adding relays for the headlights is very easy and despite some comments is neither complicated not does it require lots of extra wires.

Mine needed a power feed cable which has an in line fuse in it, and a short earth wire. Those are the only new additions, the rest of the wiring is already in place. I just cut into the main and dipped beam wires to connect direct to the two relays.

The relays are housed in a plastic box fixed to the front O/S splashguard. It came from a scrapyard car (MK 2_Astra) with slots for 4 relays: Main beam, Dipped beam, radiator fan and a blank which holds a spare relay in case I ever need one to swap over.
GuyW

Thanks Nigel,
I suppose I'll see what happens when they're installed. I spoke to the chap at Classic car leds just in case I'd forgotten anything but it seems what I've ordered will work. He has an MGBGT and was both informative and very helpful even advising the colour of the positive lead for the electronic flasher.
Jeremy MkIII

This thread was discussed between 05/12/2019 and 08/12/2019

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