Moss Motors, Ltd

I have a 1977 MGB that I've been working on for a while. I have an oil pressure gauge that works. Most everything else electric doesn't. Water temp, fuel, speedometer, cigarette lighter, radio, clock, signals and backup lights don't work. I really suck at electrical stuff. How should I proceed to get things to work? All suggestions accepted. Minimum sarcasm please.

First get a good wiring diagram to give a baseline to start from.  http://www.advanceautowire.com/ has some great MG diagrams. I think the biggest problem with 'lucas' issues is dirty contacts. I clean every connection i can get my hands on. I also add a small bit of dialectric grease to each contact as I go. Make sure the grounds are clean and tight as well. Many MGBs have been the victim of 'bubba' wiring and that has to cleaned up as well. Start with one problem and work through as you have the time. Do not forget to drive the car though :-)

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Alfred, Maine
63B Waiting for resto
63B Donor
67B Ours
73BGT Mine
73BGT Hers

Start with clear wiring diagram, first checking and cleaning all grounds, work from battery back towards all instruments using digital voltmeter to see where you are losing current.

<><>There was a web site in England that had a superb troubleshooting and repair guide for MGB electrical systems.   I just visited the site and he has closed it because he is publishing a book with the data contained in his web site.  I did find the book on AMAZON.COM being sold (pre- published sale)  for about $20.  It is by Rick Ashley and ordered one for myself.  I have used his information and found it excellent and easy to use.  The oil pressure gage is mechanical,  no electricity to make it work.  Water temperature and fuel get their voltage from a voltage regulator that is mounted just forward of your left knee when sitting in the car, sort of near the hood release lever.  rectangular box about 1" long.  It regulates the voltage to those two to ensure the same reading regardless of the system voltage.  The speedometer is mechanical and is operated by a cable running from the transmission to the back of the speedometer. It does have a light in it that comes on with the dash lights. Cigarette lighter, radio, clock, turn signals and backup lights all are electrical and come from different places.  I would first check the fuse box in the engine compartment and see if there is voltage to and from it to each circuit.  Another book you need is a Haynes manual for the MGB available from MOSS or British Victoria or your local auto parts store.  Probably not on the shelf at the local store but they should be able to order you one in from their warehouse.  Loads of great information and wiring schematics in the back of the book.  I took the book to a local Mail and more shop and had them blow up the schematic for my 78 MGB to about four times the size and now have something that I can use to trace wires that keeps you from getting lost in the schematic.  You can use colored highlighters to trace out individual circuits.  One of the major causes of problems with my car was OLD and corroded connections.  I cut off the connectors and installed new ones.  Ground connections are also a big problem.  On the schematic you will find ground points where several circuits use a common ground, usually a sheet metal screw.  When you locate one of these, remove the screw, clean the area to bare metal, buff the wire terminals hooked to the screw and reconnect.  Be surprised how things work after that.  Also see if you have a sports car club nearby, go visit them and ask for help.  You can find some really great people who like, restore and drive older cars.  Does not matter what make or model.  The electrical system in a MGB is basically the same as one in a U.S., Japaneese or European car.  Except it is made by LUCAS, the prince of darkness. :-)
Long winded but maybe some help.

<> 

Speedometer works off a cable attached to the transmission, it is not electrical.

Backup lights, temp and fuel guages, signals are powered by the green circuit, third fuse down in the fuse box.

 Clock and cigarette lighter are powered by the purple circuit, fourth fuse down in the fuse box.

Can't say how the radio is powered due to the fact it is usually up to the installer to decide.

 Start at the fuse box and use a meter to determine if you have power going through the fuses.  Contacts on the back of the fuse box can become loose and corroded and prevent continuity.  Make a couple of enlarged copies of the wiring diagram for your car.  One for reference, and one to make notes on while you are checking the connections.  Clean all connections and use dielectric grease to prevent future corrosion.  Replace any faulty connectors.

Lucas stands for

Dim

 Flickering

  OFF

aka Richard w/ 71 split bumper B

Thanks, I will start to clean and check as required. I appreciate the help!

Ziggy,

 

could you post the real title or isbn? I've heard of this and cant find it in amazon 

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Old Fart
71 GT project
73 Roadster runner

I actually have this book. It is MGB Electrical Syatems by Rick Astley published by velocebooks.com.

As others have said, fuse box & connectors.  Since you have complete circuits dead I would start with the fuse block.  I've run into this problem before and it's usually poor contact where the fuses plug in.  There are only 4 fuses and one loose one will affect complete systems as you describe.  The bullet connectors are suseptable to corrosion also since they aren't sealed but  you have so many inoperative items that I would definetly bet on the fuse block.

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72 MGB 80 TR8
Pittsburgh PA

Sorry, here is ISBN Number:

Mac-

Here's a link for Rick Astley's book

http://www.amazon.com/MGB-Electrical-Systems-Essential-Manual/dp/1845840577/sr=1-3/qid=1161156212/ref=sr_1_3/002-5598823-4362433?ie=UTF8&s=books

Amazon has this available for "pre-order" which means they won't have it until late December.  Some folks already have copies.  Who is selling them right now?

 R.

 

Jeff Zorn at www.lbcarco.com is the US vendor

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Alfred, Maine
63B Waiting for resto
63B Donor
67B Ours
73BGT Mine
73BGT Hers

I agree, the best advice is to check all grounds first. Most electric problems go back to ground. Start with the one in the trunk that goes to the license plate. I make it a practice on those cold winter nigts when Im just tinkering with my car to take apart the male wire nipple and clean with a dremel or steel wool. The wire nipple is in Moss catalog page 89 look at number 35 in the blow up for referance. For cleaning the female portion I have a very small jewlers file that gets in there real well. Put it back together with a bit of dielectric grease. The Dremel with a small wire wheel is a great tool for cleaning.

 

Michael

 

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Where there is nothing to lose and a great deal to gain if succesful by all means try.