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MG Midget and Sprite Technical - Indicator problem

My R/H front indicator is misbehaving. When I operate it the side light bulb flashes but not the indicator bulb. I haven't yet checked to see if the bulb is O.K. but there is clearly a glitch in he matrix. Where should I check first? Obviously a wiring problem but where to look.

Had a one hour drive this afternoon on roads which were not cluttered by Parisiens (the Dordogne is full of Parisiens in August) and the car is better than I had hoped for. It really rewards thoughtful driving. Brilliant!
Roger D

Sounds like it might be an earth fault so check the indicator earth.
David Billington

What bulbs illuminate when you just put the sidelights on ?
richard b

Second vote for earth being the root cause of the problem.
Jeremy MkIII

Richard makes a good point but it could be also and in addition be poor earth and wrong wiring and/or poor connections.

Easy way to test the earth is to run a test wire from the battery earth post to the sidelight unit.

But I'd remove both side light units and check and clean the connections live and earth, clean the bulbs glass and base and connection, and clean the inside of the lenses and reflectors. It can be very surprising how much a little debris inside the lenses and on the bulbs can dim them and how much brighter they are when cleaned.

Then I'd do the same with the rear lights, check and clean connections and clean lights. Very important the rear lights are as bright as can be, side/brake, indicators, number plate, (reversing) all help to be seen and what your doing.

Don't use polish on the reflectors just wipe clean, I made that mistake and it polishes away the reflectors.

I think it's a good idea to check and clean and repair as required all electrical connection from the battery posts on, can be done in stages and as part of work already going on. Helps to find and prevent issues and once it's done it's done for a (hopefully) very long time.
Nigel Atkins

Thanks all. I'm just going to try the method described by Nigel, hadn't thought of that.
Roger D

I had to make up a kit to test the reversing lights when I first got the midget. Just a length of spare twin wire that was long enough to go from the battery terminals to the furtherest point on the car. Each end I have spade connectors to which I can fit tails with a selection of terminals to cover all connections. Battery end I have some big clips off my old 'smart' charger.

You can get a probe with a point on it that does similar and much more but I prefer the direct clean approach.

You can also add in to the wire test lead a bulb and/or switch for testing and diagnostics.
Nigel Atkins

Tried the test wire and it's definitely an earth problem. If I run a wire from the battery earth to the bulb and it works as it should. There is no significant corrosion in the bulb socket so I shall have to look elsewhere, not quite sure where. Perhaps the body of the unit, the reflector, is not making clean contact with the metal of the bodywork.
Roger D

Roger,
the whole backplate of the front side lamps assembly AFAIK earths out to the body by the two captive threaded screws so the body of the car at that point and the captive screws and nuts and washers have to be reasonably clean (of paint) and free of rust for a good electrical connection.

As I remember it the nuts are of some bloody silly and awkward size like BA or obscure UNF but not metric but it doesn't really matter as long as you don't strip the thread on the backplate and get a clean (secure and protected) electrical connection to make a good earth.

It's just one of many areas of farting about that some find nostalgic and fantastic, not me obviously.

For the rear lights backplate I just added additional wired earths as it's all neatly in the boot but not so easy with the front lamps so I farted about and cleaned all up, as I wouldn't want to loose any concourse points.
Nigel Atkins

Yep, farting about I do well.
Roger D

I try not to rely on the lamp body earthing to the car body. I will generally add a separate earth wire from each lamp unit to a well earthed bolt nearby.
Mike Howlett

Roger,
you might enjoy it, and good luck to you, but if it's to do with cars, particularly my own and it's some over-priced and over-valued old car called a "classic" I don't, but I know others on here get perverted pleasure from such stuff and good luck, whatever floats your boat, gets you through the night and doesn't do (too much) hard to others then great.

If you like farting about with your old over-priced and, well you know, I've lots of good ideas to while away the ebbing life and lifeforce that are (semi-)productive in saving time and hassle in preventing future hassles.

Or like many you may enjoy the frisson of tackling problems as they arrive particularly if you can wear your underpants over your trousers and be a roadside repair (or not) hero - showing how clever you are to have found the issue (rather than having prevented it).

I really don't fit in here, but I give a real-world cynicism to the grammar and private school jolly hockysticks of MGs are brilliant (they won't get the reference).
Nigel Atkins

Nigel,
Farting about, was not an expression of desire to delve into the intimate parts of my car, in fact I would be happier if everything was in good working order all the time with no intervention from myself. However as and when these little inconveniences do crop up I try to sort them myself rather than pay someone else to do it.

Following on from the indicator problem, now solved by making a good earth, I find that I have no main beam from the headlight on the same side. The bulb is good and it doesn't seem to be an earthing problem as the dipped beam works O.K. I have put a meter into the sockets that the bulb plugs into and both dipped and main beam give about 11.6 volts but for some reason the bulb is plugged in it will not light when main beam is selected.

Logically this would point to a poor connection in the terminal block on the main beam feed but wiggle as much as I can it don't work.
Roger D

Roger,
even when a paid expert is doing some of this stuff it's still farting about.

You say bulb, are you not with sealed beam units.

Try swapping the unit or bulb from the other side, you can clean connections for both sides then.

Check the wiring is correct both sides, blue/white for main and blue/red for dip (as I always think it should be red for main). You can't have the headlight connector wrong as it only goes on one way.

The bullet connectors behind the grill often cause issues, RHS has one set but LHS has two sets. 11.6v doesn't sound a lot but it depends on your meter, car battery, wires, connectors, switches, weather, standing on left or right leg, ect..

O/T - seeing your useful 'Vehicle profile', are your tyres 155/80R13?
Nigel Atkins

I forgot to put - again a test lead of the battery with a switch to the unit will test it plus perhaps show the losses in brightness to the dip beam at least.
Nigel Atkins

First point of call for many electrical problems is a poor earth. Get yourself a multimeter that measures resistance. Mike's suggestion is a very wise move.
Oggers

Nigel,
Tyres are 145/80R13.
Don't think the wiring can be wrong as the light was working earlier and I have changed nothing.
Oggers
I have such a multimeter what resistance should I be checking?
Roger D

Agree first port of call for head lights is the bullet connectors behind the grille.
Especially the new Lucar rubber units - I had some in a new loom that were plated steel (original was zinc on brass) and they were a major source of problems.
I remember at an MOT one headlight failed to light (checked OK at home)and as the tester pointed it out the other one went out in sympathy ! fortunately it was my local friendly garage !

R.
richard b

Roger,
that for tyre confirmation.

What happened when you swapped the light unit/ bulb from the other side?

I was initially wondering it was just a 'bulb blown' (or filament).

I'm not a big fan of cheap digital multimeters as they can be inconsistent and unreliable - as it worked for the side light it'll also work for the headlight to test the earth, just run the test wires from the battery directly to the bulb/unit, you can test main and dip one at a time by connecting the live wire and leave the earth wire on the earth connections. That's the light properly load tested.
Nigel Atkins

Roger

Stick it on Ohms - Check you are geeting zero or very low when the probes touch. Measure resistance between earth connection on the component and a good earth on the car. If you have a good earth, reading will be pretty much what it was when you touched the probes. Bad earth means high ohms, infinite ohms or open line - usually shown as OL on the readout. Move along the earth wire to pinpoint the fault

Alternatively if the component only works when you use a jumper wire from the compement to a good known earth, then you also have bad earth. Hence Mike's suggestion.
Oggers

This thread was discussed between 03/08/2021 and 06/08/2021

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