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MG MGA - Brake Switch Wiring

Let me start off this by saying I think we have a resident ghost. Named Nan Clark, she came here with my daughter while a major rebuild of her house was taking place in Mill Hill - and still is. The ghost is searchable on the internet. I think she is playing tricks with me at the moment. I got 2 biscuits out of a tin the other day. I was eating one of them, turned my back for a couple of minutes. Came back and there was 2 again on the table!

Anyway, my car was fully working about 4 weeks ago. Due to circumstances I have not been near it until yesterday. Got in it and the brake lights do not work. Got the torch out to have a look at the switch and noticed that there are 2 cables attached to the switch and another dangling free adjacent with a spade terminal on it.

There is a green cable attached to one terminal and a green with black stripe attached to the other. The one dangling free is a green with purple stripe. According to my wiring diagram the one dangling free should be connected to the switch. The green with black stripe is for the fuel tank sender to gauge and should not be there. The fuel gauge is working fine. What is going on? I am mystified. The only thing I would add is that I split the direction indicator wiring away from the stop light circuit about 3 years ago. They are working fine.

The ghost is very cunning. She is always stealing daughter and Son in Law's car keys, never to be found again. Over in their other house in Italy last year she started up my daughter's locked and empty Porsche Boxter while she was sitting on a veranda on the phone. She rushed inside, got the keys; went out to the car and as she pressed unlock the engine stopped. Porsche say that is impossible. Cannot happen.

Steve

Steve Gyles

Steve, brake light switch leads would typically consist of "green" and "green with purple" wires. "Green with black" runs from fuel gauge to fuel tank sending unit. Perhaps someone rewired the car at one point and used available wiring to fix existing circuits. You can look at the fuel gauge and see whats actually connected to it and do the same for the sending unit; this may shed some light on whats going on. It could be that your wiring is OK, although not original, and the switch itself is not working. You can test the switch by bridging a wire between the terminals and see if the brake lights turn on; hopefully they do.
Nick Kopernik

Nick

No one else has ever touched my car since I rebuilt it in 1996, installing a brand new loom in the process. I actually did a full light check before using the car last time. Something I do very frequently. As I said in the opener every other electrical circuit is working. The green with mauve stripe wire is hanging down beside the switch. It has a slightly distorted spade terminal. A green with black stripe is connected to the switch. I have never seen a third wire hanging loose in that area (whichever colour stripe) before. I certainly would never leave a bare wire hanging free.

I repeat, no one other than myself has ever been inside my engine compartment.

Steve
Steve Gyles

Is your garage slightly damp Steve?
If it is, it could simply be that your MGA is showing signs of life and it is responding to the dampness by pushing out new roots!

Just make sure you move it more often! :^)

Seriously though, I have taken a pic of my brake light switch (attached) and there is no sign of an extra wire and connector.

This may be because it is a 1600 loom, or it could simply be that my garage is dryer than yours! :^)



Colyn Firth

Colyn

Perfectly dry double garage and workshop. Dehumidifier when necessary - rarely.

Too cluttered with shafts, pipes and tubes in that switch area at the moment to get a decent photo like yours. However, using your photo as my baseline I have gained a third wire (green with black stripe) coming out of the same part of the loom as your 2 wires. I swear I have never seen 3 wires coming out of it before, let alone one of them, the green with purple stripe on your photo, dangling free with a bent spade on it. The additional green with black stripe cable that should be surplus to requirements has been connected to the switch.

I am not touching a thing until I have researched further. Then I will get the car up on my hoist and investigate and get some clear shot photos.

Despite my slightly flippant, albeit true, opening post, I am genuinely very concerned, verging on scared of such happenings to a road vehicle. My son in law says this is standard Nan Clark practice. It is perhaps interesting to note that when they had their (haunted) house demolished 3 years ago for the rebuild the excavator driver left the site and would not return after he found a totally enclosed room with no windows nor door, but giving the appearance of being lived in and floored with modern carpet. Apparently as his grabber chewed into the wall his neck went very cold and prickly and he felt he was being watched.

Steve
Steve Gyles

Steve, not sure which year MGA you may have, but there are some differences between the different model years as it pertains to wiring looms. It is possible that you may have some unneeded and unused connections. That being said, none of the wires or individual connections would have included the use of spade terminals. Have you had the opportunity to use a bridge wire between the brake switch terminals? It could be that the switch itself is bad and have nothing to do with the wires themselves. I've gone thru a new switch every couple years as the replacement units on the market today seem to fail quite frequently; even the one I installed this past spring seems to require more pressure than ever to get the light to turn on.
Nick Kopernik

Just now I tried to get a camera shot of the switch and the loose wire but without success. I then rested the loose wire (green with purple stripe) against the spade terminal of the other wire (green with black stripe) that is connected to the switch and did a brake light check. They Worked.

So it seems to confirm my suspicions that the wires have been changed over. But I have no idea how or by whom. Also I have no idea what the other wire is for. Never seen it before coming out of the loom. I guess all I can do is attach the spade to my meter and prod around in hope.

Steve
Steve Gyles

Believe in ghosts if you want but please don't believe in the marketing of how good all German engineering is! Porsche (and BMW) owners report electronic problems that Porsche (and BMW) say don't exist, same way VW and others didn't cheat emissions and Ford didn't value production costs over lives. Car manufacturers cost in fractions (of a penny even) despite their huge turnovers, rectifying and altering production errors, recalls, etc. may involve lots of cost and not in fractions of a penny so are often avoided even when they shouldn't be. That's without the fear of "interventions" like standards and worse still litigation.

For the wires, it could just be your memory failing in this instance, many times I find items not where I "knew" I'd left them but where I "knew" they wouldn't be. Only yesterday I repeatedly looked for an item only to find it today where I'd already looked several times before (a man-look as my wife calls it).

Human memory is a very strange thing and not fixed or stable as you might believe, it can be altered by time and influence, and overwritten if you like. A memory can become a belief, accurate or not, some people have such a strong belief of a memory or sometimes their own (conscious or unconscious) manipulation of the memory that even when shown solid evidence can dispute the evidence and stick with their belief.

Examples are in the news daily, but one of the went back to the USA. :)
Nigel Atkins

Steve. in your first post you mention that you "split the stop light circuit from the direction indicator circuit". I'm not sure what you mean by that if you have the 1500 relay unit and you still use the same bulb for stop and indictor. Also you have a high level brake light from memory. Is that fed from the switch or the back of the car? The green/purple wire is on the ground/lamp side of the switch, so if the Green/black wire is on the same terminal it is switched.

As you say the only Green/Black wire on both 1500 and 1600 loom is to the fuel gauge/sender unit or headlamp flick switch and relay which probably wasn't standard. I can't remember where the bullet connector is between the sender and gauge.

John
John Francis

This thread was discussed between 04/12/2019 and 11/12/2019

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