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MG Midget and Sprite Technical - A most peculiar problem

This is driving me wild, please can someone help:

When the lights are put on full beam, they both dim to a bizzare orange glow, as if the bulbs are on their way out.

When they are flipped back to normal (dipped) the near side light goes off and the off-side light goes to full beam.

Added to this, when the lights are switched on, if i depress the brake pedal and then switch off and remove the ignition key, the engine continues to run until i take my foot off the brake pedal......!!!????

This is most irregular im sure you'll agree.

Any troubleshooting suggestions will be greatly appreciated!
J Price

When one circuit's functions are not independant of another it's almost certainly a dicky earth connection. It would appear that you have at least one.

What's the history? Did this all start happening at once? Has the car been standing? Have you worked on the loom or recently replaced any electrics on the car?
Ant Allen

agreed, all very symptomatic of earthing problems. Check the bundle of earths on the terminal on the offside front inner wing...
David Smith

As the car is not used too regularly it is difficult to ascertain if the problems all started at the same time. I have not been messing with the loom recently and the car has been standing a lot....outside.

Is the fault situated in the lack of a decent earth?

Should I have a snoop around the fuse box and inspect the wires to see for any poor connections/bare wires etc?

Thank you for your help chaps, much appreciated.
J Price

It's going to be a tricky one to diagnose. First off I'd disconnect both headlamp connections and the brake light switch and see if the engine starts / stops correctly. You need to remove things until you have a minimum set of electrics working correctly. Then build upwards, testing the existing things as well as the added systems at every stage. That should identify which circuit is causing the fault (or faults - sounds like there's more than one to me!). Then consult the wiring diagram. A resistance meter is good for finding poor earths, but beware of measuring seeing a "good earth" without any current actually flowing. Better is to switch on the circuit and then check that the earth side has 0v between it and the battery negative post (I assume neg earth vehicle).

Let us know how it goes. I'll be doing a similar job on my car in the next few days as I have to get my dodgy electrics working once more.
Ant Allen

Ant: almost certainly a dicky earth
Me: symptomatic of earthing problems
then
JP: Is the fault situated in the lack of a decent earth?

I give up...

David Smith

I disagree about a bad earth,

My guess is a previous owner was murdered in a firey crash while in the car...Its going to take a sieth to solve this problem.

Always look to the obviouse solution.

Prop
Prop***The End in 2012

Maybe Prop, but what the hell is a sieth???? Is it a specialist psychic investigator ?
Graham.
Graham P 1330 Frogeye

J.Price,

is this afd396j? if so maybe you are now bored of it and want to get rid of it? maybe you want to sell it back? after all you did say its been standing. I used to use it every day!

I do miss my green car,
John


John Collins

Bizarre orange glow = bad earth
When they are flipped back to normal the near side goes off = no voltage to or burnt element in that bulb
Car keeps running when foot on brake pedal and key removed = The Scions Of Lucas (check that acronym) are in the house... good luck with that...

R
Richard 1979 1500

John: Yes this is your beloved green midget we're talking about, and don't worry, it does normally get used all the time but it failed it's MOT and has been off the road whilst I fix it so it doesn't get clamped!

You may be pleased to know that the midge now has a new engine too.....I did a nut and bolt rebuild on it and addedd a few toys for good measure to make it go a bit quicker. I'm currently working on a Webber carb for the summer....I'll keep you updated on it's progress.

David: You have correctly identified that I am a halfwit

Thanks for the earthing suggestion though, i'll bear it in mind when I spend the weekend electricuting myself.

J Price

jp - I'm sure you're not ! - but do read the answers here, it's usually pretty good especially when there's a concensus ;-)
David Smith

John!

I told you so

I told you not to sell that blooming car, you'll be sorry I said...

jp, not a "halfwit" if you had the sense to buy John's lovely motor...

but what David says is so true

remember that not only are there earth points on the offside inner wing (well mine are there!) but the earthing wires are also in the loom at the bullet connectors (any black wires)and they as well as the current carrying wires get corroded inside the bullet joints

fine sandpaper and Vaseline will renovate almost every joint quite easily even if it takes a bit of doing

Although the earths are almost sure to be the culprits it can be a bad joint at the "in" wires too that cause the volt drop you see as an orange glimmer
Bill sdgpm

I agree with the bad earth idea and disconnecting both headlamps (all connections should be disconnected!) and see if the other problems persist. Disconnect electrical system one component at a time and check symptoms as you go. Then build back up. That is good advise.

Now, this is a time to be happy about the relative simple electrical system of an old car. A friend of mine had a SAAB 9000 that started acting up. First it had the problem that it kept running as long as he had his foot on the break even if he removed the key. Then the rear window heater went and after that the automatic climate control. Seemed like there were gremlins in the car. After a lot of google time he found an odd tip in a corner of the web that solved the problem. He simply replaced the bulbes in the rear lights with a different brand and all the gremlins were gone.... Now that is an unexpected problem if I ever say one. :)

//Erik
E Lindgren

J Price
Hi Your car continuing to run with lights on and foot on the brake is caused by a short in one of your taillight globes. You will probably have your park lights coming on when you put your foot on the brake with all the lights turned off as well. With your lights turned on and your foot on the brake the power from the light switch flows through the shorted globe back to the brake light switch and while you have your foot on the brake it will flow through the switch and power the ignition causing the car to keep running until the brakes are released or the lights turned off. As far as the headlights go it sounds like an earth problem but it could also be a short in that nearside light.
Hope this helps Willy
WilliamRevit

Now that is what I call service. Coming up with that solution is pure genius. Well done that man. Please tell me it is a case of "been there done that", otherwise you're in a different league to the rest of us!

Ant
Ant Allen

Thank you for all your help chaps....I worked on the car all weekend to get it through the MOT which it should duly do tomorrow!

The front light issue was owing to the earthing cable having slipped out of it's socket. I disconnected all the wires in both lights and went at them with some contact oil.....naturally the last one I came too was the one that fixed it!

The brake pedal/ignition debacle was a fault identical to the one Willy described. Tidying up the wires to the rear tail lamps solved that issue pretty sharpish.

JOHN: I've attached an image to tug on the heartstrings and prove that midge is being put to good use!

So there we have it.....those of you who remember the over compression issues I was having when I built the new engine last summer will pleased to hear that a decompression plate as finally solved the pinking problem.

The car is now simultaneously impressive and terrifying!

Keep an eye out for it over the bank holiday weekend if you're in the somerset area as it will be migrating from London to Glastonbury for the holiday!

Cheers again


J Price

Still looks a nice car John

good news about the earths and lamp problem, the BBS vindicated again
;-)
thanks for telling us
Bill sdgpm

This thread was discussed between 02/04/2009 and 06/04/2009

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.