MGB & GT Forum

Folks,

Love my B, but I am having problems with headlights, taillights, dash lights, and brake lights staying on and working all the time. Being a mechanical nincompoop it is beyond me to inspect and trace wiring and all that jazz, so I suppose what I am asking for is a good reasonable mechanic in the Nashville, TN area to reveal himself/herself to me.

Anyone out there? Anyone?

Many mechanics don't know electricals either, and you could end up spending LOTS of money to fix your problems bit by bit .

You don't say what year you have, but MG electric's are REALLY simple. Get the Advance Auto schematic for your year. Make a few larger copies, keep one in car, and bring one into the can with you to study. It will soon make sense.

Your problems are simple. Find out where all your grounds are, and clean contact areas well. That might help some or all problems. If not, buy a bunch of female bullet connectors and a few males, and start to clean. Search here what people do. Clean or replace. If you spend a few hours and do all in your engine bay, cleaning light sockets, and providing all is well under dash, you'll have years of trouble free driving. If you love your B now, your feelings will only grow with YOU working on it.

So what if you pay someone to fix something, and you have a different problem miles from home. If you're intimidated, you may just pay for expensive tow. If you've taken time to understand and fix, this new issue you will tackle with confidence.

Ignorance of your electrical system is no excuse, and should be against the law.

Ralph,
I was probably more ignorant than you when a daughter and son-in-law bought us a '76 B a few years ago. There are now 3 B's in the family and we learned a lot from them. In the B that Todd and Anitra bought us, we had the same problems you're dealing with. We downloaded the electrical schematic (it is much simpler for the '71 than for the '76, btw) and I printed out several copies, took a highlighter and traced each circuit on a separate sheet.
Here are some simple steps to take after downloading your schematic here: www.advanceautowire.com/mgb.pdf


1. Replace your headlamp switch (two good sources are bpnorthwest.com $12.58 and northwestimportparts.com $15.00)
These rocker switches are notorious for going bad and causing the kinds of problems you mention.
2. Purchase a relay switch to take the load off your headlamp switch to extend the life of your switch
Just replacing the switch should take care of the problems you're having, but at some point it is a good idea to install a relay to take the load off the switch.

If you still have problems with specific lights not always working or being dim, go through and clean your taillight, turn signal and headlamp electrical connectors in the trunk and under the hood. Applying a dielectric grease (available at your local auto parts store) to each connection helps. If some of the connectors have weakened due to age, Northwest Import Parts has inexpensive replacement sleeves and bullet connectors.
Like Gary in BC mentioned, the second step is to go through, clean your ground connections (black wires) where they attach to the car body and apply dielectric grease to these connections, also. I know it sounds counter-intuitive to be greasing connections, but dielectric grease inhibits corrosion which is a greater detriment to a good connection and the thinness of dielectric grease allows a solid connection while inhibiting the corrosion.
You may not have to go through the wiring schematic at all if you follow the steps above and simply clean the connections. If you have additional problems (as we did due to some additional non-working items), then the schematics are a good place to start.
In addition, the libraries at mgexp.com and chicagolandmgclub.com are very good. Who knows, you may write an article for the tech library someday! I have one hosted at chicagolandmgclub.com about sway bars and I was the worst greenie there ever was (still am in most respects).
There are also some really knowledgeable people on this site. I have a favorite who wouldn't want me posting his name here and so I won't, but you'll get to know some of the regular posters (I don't like to, because I know so little compared to so many). But having started in at least as poor a state as you and with one of our problems being the same as yours, I wanted to post and encourage you to dive into working out the problems with your B. It becomes easier and more fun with time.
Gary
thepeggasus



Edited 2 time(s). Last edit at 2017-01-16 03:36 PM by thepeggasus.

++ on many most mechanics not understanding electrical. Guess how so many of our cars got so screwed up?

Owning a LBC means you need to do things yourself. Electrical gremlin problems ate time consuming and tedious. Do you want to pay someone $75 an hour for days to come back and say he cleaned up one bad crimp just to have another issue on the way home? The Internet is full of really basic classes on DC electrical theory. Spend a couple of hours until you understand Watt, Ohm, and Kirchhoff. Simple arithmetic, so don't get worried. You can actually visualize water flowing through pipes. A little knowledge will go a long way.

Then get the drawings from Advance for your car. They do make it easy with color coded wires so you can find the ends even though the wired vanish into bundles.

So the above folks gave us Laws. I offer some rules:
There is no such thing as a good connection. Some are just worse than others.
The "engineers" who designed the car were idiots. If they could design it, you can fix it.
Electrical tape has no place in an electrical circuit. Just like Duck tape is not for use on ducts. Same for wire nuts and the most evil thing of all, the Scotch-Loc connector.
You can't diagnose electrical problems without a basic multi-meter. Today's electronics makes then cheap. A $10 will work, but for $35 you get a nice one. If it has a "Low Ohms" scale, that is a bonus.
Real crimpers have a compound action and ratchet to ensure enough force. A crimp without enough force is a pregnant crimp. It will give birth to a failure in the future.
Dialectic grease is your friend. It is how you keep a good connection good by preventing moisture from getting to the contact area. It pushes away from the actual contacts points. The reason the rocker switches fail is the grease inside has dried out so the contacts oxidize. That means they don't conduct electricity well, heat up and get worse.
Biggest thing to remember: Take one problem at a time. Don't get concerned how busy the drawing looks. Take a highlighter and follow the circuit you have trouble with and ignore the rest. The drawing does not show ground. They use the body of the car for the source of electricity ( yes negative is where the electrons come from). So you can highlight from the drawing ground back to the battery negative terminal to complete the circuit.

---

Cogito ergo sum periculoso

The lights stay on "all the time"? How do you turn them off when you're not driving the car? Knowing the answer to this will immediately cut the problem search in half.

Electrical troubleshooting an MG is about as easy as it gets. Simple DC current and no on-board computers. You'll pay a fortune to pay someone else. Bite the bullet and buy a cheap multimeter and a test lamp. $20 will do it. Then go on Google and research DC circuits. In the end, you'll be glad you did.