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MG MG Y Type - Lighting problem

I have what appears to be a wiring problem with my YA. When I apply the brakes, the front side lights come on (as well as the brake lights). It was suggested to me that the brake light circuit may have been wired up as the side lights and vice versa. However, when you turn on the sidelights, both front and rear ones come on. I know nothing at all about electrics, but I had a look at the wiring diagram (just for fun), which seems to indicate that the two circuits are completely separate. I'm sure it must be something fairly simple as the rest of the electrics appear to be fine. Could it be a bad earth for example? Any suggestions or advice (preferably in non-technical terms) would be gratefully received.
Andrew Adamson

Hi Andrew

Like you it was a complete black art Car Electrics.

There are two immediate solutions to the problem:
1) Paint the side lights red and use reverse! or
2) Look in the Yellow pages for an Auto Electrician and also ask at your local natter for a recommendation. There are good and bad ones - you need a good one.

It is more than likely and earthing fault, but tracking it down as a novice is not the easiest thing in the world.

Also something to consider is the state of the whole wiring loom. If it is old or original, it is also probably very brittle. New ones are available (from Autosparks in Nottingham - link on site) very reasonably and you can also specify whether you have indicators and / or trafficators or both, and how they are operated, and they will weave the loom for you. You can also have it cotton braided black with white flecks - just like the original. Then get someone who knows what they are doing to help you fit it. You will (like me) learn loads from this!

Best of luck tracking it down and sorry I cannot be more helpful - not my strongest field!

Cheers

Paul
Paul Barrow

Sound to me as an earting problem too, but maybe not so complicated. Following is my theory!

Most probably the spare wheel cover, on which the rear lights are mounted, isn't earthed properly to the chassis/body or the connection rearlights/cover is bad.

When you apply the brakes, the brake light searches for an alternative earth and finds it in the circuit of which the sidelights are part of.

As a result probably not only the sidelights come on when you brake, but also the rearlights.
An other sympthom would be that when you turn on the rearlights it will earth via the brake light and, if my theory is right, unknown to you the brakelight should also come on (a little less bright than normal).

Final check is to turn on the rear-/sidelights, and apply the brake. The lights will turn off (the currents of the to circuits "collide" and don't go anywhere), or maybe one or two lights will burn less bright.

Cure for all this would be to connect the spare wheel cover with a fresh wire to the chassis/body.

Happy hunting!
Willem van der Veer

In addition to above
Cure for all this would be to connect the spare wheel cover with a fresh wire to the chassis/body and/or clean all the earthing surfaces of the rear lights
Willem van der Veer

Hello Andrew

As previous replies have indicated, the most likely fault will lie with the earth returns from the two D type taillamp assemblies.
There should be ( I'm going by my car) an earth wire which joins the spare wheel cover to the two lamp assemblies and is attached to one of the right hand body to chassis bolts in the spare wheel well. There are two bolts each side, and if you use a serrated or star type washer between the wire terminal and the body, you should get a decent earth.
Consider that the earth wire needs to carry all the electrons energising the stop filaments, so if you have two stop lamps the earth needs to carry twice as many electrons as the individual lamp wires.
If the earths are poor or non-existent, the current will flow 'backwards' through other globe filaments to ground and so complete the circuit to earth. This can make an assortment of lamps glow!
Electrics is NOT a 'Black art' it is basic stuff, but you shoul ddevelop a basic understanding of the fundamentals.

Assuming the side lamps do not power up the brake lamps, there should not be any crossed wires or shorts in the harness.

Bye for now,
Geoff Meller YT3477
Geoff meller

Many thanks for all your help and advice. I think I've got something to work on now. I noticed on the way home from the Bradford to Morecambe run last week that the headlights have a tendency to go on and off by themselves! (Luckily it was still before lighting up time) Presumably this could be the same earthing problem? I'm not sure how old the wiring is, but I have a feeling it has been re-done in the not too distant past. Any ideas on how much a full re-wire should cost to have done, should it be necessary?
Andrew Adamson

A loom should cost about £120 - Harry Crutchley has one at the MG Octagon Car Club but I am not sure a) how much he wants or b) if it has any customisation. I had my loom from Autosparks direct a few years ago and it was £120 including cotton braiding (Black and white) and fittings for semiphors and trafficators. They do not include the steering column in the standard kit, but you could deliberately ask for it.

Fitting - buy the Y Data Sheets from Regalia and just take it slowly. I did my Magnette after I paid someone about £400 to do my Y! It is pretty easy really though and Autosparks were extremely helpful on general advice although they cannot be car specific.
Paul Barrow

I just got a braided loom for my YB for £60.00 from AUTOLOOMS LTD 4 College Street,Hull Tel:01482 706505
John Arkley

Check the price with Autosparks too - I might be wrong - it was a while ago.

Paul
Paul Barrow

This thread was discussed between 10/09/2003 and 18/09/2003

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