Moss Motors, Ltd

My 77's brake lights are out. Both of them are out, so I assume it is the switch and not the bulbs. I have never had to remove the brake light switch on an MGB. I see that the earlier switches are located on a cross under the car and so I am assuming that they are hydraulically actuated. But mine is in the engine compartment. Is it also hydraulically actuated, or mechanically?

zach 

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Happiness is an MGB!

Zach, it's a mechanical switch located on the front of the pedal cover in the engine compartment. If you have the power assist brake assembly it may be mouted on the rear, I can't remember for sure on that one. The new switches have been a little on the unreliable side, so a lot of guys recommend installing a relay to take some of the electrical load off the switch which makes them last longer.

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'73 Midget (V6)
'59 MGA (I6) under construction

"There is a fine line between a hobby and mental illness"

Just for fun, check your lamps. Both of my brakelights went out on my '80 B, I thought for sure it was the switch, 'cause they couldn't both go at the same time, could they? Yes they can, and yes they did!

 

Dave

Bill,

This is a strange one. I thought it was most likely the stoplight switch, but I disconnected the wires from the switch and put a jumper wire between the two connectors and the brake lights didn't come on. I checked both bulbs and they are good. I checked for a loose connection in the trunk and under the hood...nothing. I played with the headlight switch and the brake lights worked; for a while. Later, I noticed they were not working again and jiggled the headlight switch. Couldn't get the brake lights to work. Turned the ignition switch on and off and the lights worked once, but not again. I don't want to have to replace all the switches, is there a way to troubleshoot this and determine which is bad?

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Happiness is an MGB!

zach,

At the risk of stating what you might already know, the ignition must be on for the brake lights to work. Also, make sure the "gang ground" in the center of the boot is tight. Then, start tracing the "power path" using the wiring diagram. I'm sure you'll find the intermittent interruption. Good luck. 

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Motorbill
From Lola to Land Rover, If it's British and has wheels, it's likely I've bloodied me knuckles thereupon

Bill,

I was aware of the need to have the ignition switched on, but don't assume I know anything else. Every day, I learn something new about this little British car. This latest problem is probably the car's way of telling me not to get too complacent over how well it's operating. The first I realized the brake lights weren't working I was driving through my little home town, enjoying the sights and thinking how this car fits like the proverbial glove. That'll teach me! As for your statement about the gang ground "in the center of the boot", what boot?

By the way, I enjoyed your comparison of Triumph vs MG.

zach

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Happiness is an MGB!

zach,

Boot is British for trunk. Look along the rear wall under the latch area. You should find a host of black wires fastened to a stud. This is the gang ground to which I refer. Let us know how you're doing.

I'm glad you enjoyed the MG/TR thing. I had fun as well. I hope I can come up with another such topic soon.

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Motorbill
From Lola to Land Rover, If it's British and has wheels, it's likely I've bloodied me knuckles thereupon

Zach - When you find the gang ground, see my article on Ground Point Preparation at: http://homepages.donobi.net/sufuelpumps/Other_Subjects/Electrical/General/Ground_Point_Preparation.pdf for tips on making sure that you have a good solid ground.

Cheers,
Dave 

This is one of those frustrating problems. This morning, I drove into town and the brake lights work fine. Of course, it's early.

zach 

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Happiness is an MGB!

"Boot is British for trunk"

 No, lets get this straight. Trunk is American for boot

 (runs and ducks for cover...)

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I want my MGB

Ed,

Here's what I want to know: When you've been out somewhere tramping through the mud, and it's time to drive home, where do you put your boots? (and don't tell me they're Wellies!) And furthermore, If you put your gloves in a boot they're not going to smell all that great. But, If they get into the cubby, the cubby's mummy might take exception to your trying to get them back. Oh, 'tis a confusing world...

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Motorbill
From Lola to Land Rover, If it's British and has wheels, it's likely I've bloodied me knuckles thereupon

Bill,

And it just gets more confusing. The brake lights have been working all day, but now, driving with the headlights on, the radio cuts out unless I switch to the parking lights, or press forward on the switch toggle from the headlight position!

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Happiness is an MGB!

Zach - that is confusing, and possibly quite unrelated to your brake light question.

Check where the radio gets it's supply - it could be that it has been piggy backed in nonstandard fashion somehow on the live feed to the lighting switch, and is loose. That, however, is pure guesswork. Also check that the parking lights stay lit when the headlights are on, to see if there is any problem with the switch.

The wiring diagram for "late model US MGB" I have shows radio power coming from the ignition switch on a white & green wire. Does the radio work with the ignition off? If so it is possibly wired differently from stock. This is quite common when radios were added later in a car's life.

Let us know what you find.

Cheers,

Ed

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I want my MGB

Bill

Funny isn't it. I never have seen anyone put gloves in the glove compartment. Sweets, sorry, "candy", insurance details and an owner's manual, but never gloves.

English vs. American "English" is a fun sport that anyone can play at home. Witness the tomayto - tomato debate at our house every once in a while, and you'll see what fun marriage across the divide can bring

Have a good weekend,

Ed

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I want my MGB

Zach, We'll leave the talk of parking on a driveway and driving on a parkway for later (by the way, why do they call it a "pair" of panties yet still refer to it as A bra?)

What I believe you may be encountering is the dreaded British Leland Lucas Achilles heal...the terminals! Those connectors at the ends of each wire DO oxidize with time. This is a very common phenomenon that attacks ALL wire connectors - even gold ones!

The fix for this actually even has a name, "re-seating".  This happens with lots of stuff (computers, TV's etc.) and the cure is often merely unplugging and replugging the connectors together. That action slightly scrapes the oxidation off of the connectors such that they make better contact again. Make no mistake, it is best to clean each and every contact since it's accessible in your hand anyway, but re-seating will often do the trick for a while.

Since the manufacture of these harnesses (wire looms), advances in terminal technology have come to pass. Not the least of which is the use of Beryllium coated copper terminals. They stand up well to the ravages of time.

First thing I would do is to trace the circuits in question and just re-seat all the connectors. Don't forget to check/clean all the grounds too!  If that helps then your problem has been identified.

  

 

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On their death bed, nobody ever said, "Gee I wish I'd spent more time at work!"