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MG MGB Technical - Fuse Box Question

Third fuse up has two red wires wih black rings around them. These are towards the rear side of the box/block. No wires going into the front side of the box at the third terminal up. Is this correct?
John
John Fraioli

John. You need to let us know what year your car is. My 68 GT has only two fuses. Somewhat later, a four fuse box was introduced. But, the attachments to any of these may have changed over the years and what I find on my 79 might not be the same as what would be found on your year vehicle. There are wiring diagrams on the internet for the MGB. Check out the ones for your year and see what the proper connections should be.

Les
Les Bengtson

John,
You should find that the tab with no wires (terminal 3) is connected directly by a metal strip within the fuse block to terminal 1, immediately above it. This should be connected via a red/green wire to the headlight switch (pin 7). At least this is true on my '72 roadster!
Richard Coombs

The car is a 1972 B-GT.
I found a 4 terminal after market fuse block at an auto parts store that I would like to use to replace the original which is not in real good shape. So, Richard does that mean I need to put a jumper from my brown wire that is connected to my number one terminal to the number 3 terminal? I assume the pins that you speak off are what I would call the spades, there are 8 spades on each side. Where do you start the counting from and which direction do you go to get to #7
John Fraioli

John. The "Diagram 13" on page 325 of the Bentley reprint of the factory Workshop Manual seems to be the one covering your vehicle. "MGB, negative earth...with seat belt warning" which should be the US version. The terminals on the fuse box are numbered 1,3,5,7 on the front side (input side) starting at the top connection. The diagram shows the number 1 and 3 terminals being connected. The rear are numbered 2,4,6,8 again starting at the top. The diagram shows only a single wire going into the number one spade terminal, red with a green stripe. This wire comes from the "lighting switch", goes to the "panel lamp switch or rheostat switch" and goes up to the number 1 terminal of the fuse box.

The back of the "third fuse up" (or second fuse down) shows two red wires (no stripes) coming out of it. Not sure what the "two red wires wih black rings around them" mean. Perhaps part of the push on connection?

Good condition used fuse boxes are available and keep the car original. If you decide to use an after market fuse box you would have to connect your red with green stripe wire to both of the top two fuses either by splitting the wire or jumpering the terminals.

Les
Les Bengtson

4-fuse boxes have the top two fuses linked together at the front so as to allow for one fuse per side for the parking lights. This can cause confusion if you mount the fusebox upside down and then connect the wires as they should be ...

The red/green wire from the main lighting switch can go to the front of either fuse. While the red/green may daisy-chain *off* the rheostat it doesn't go *through* the rheostat, if it did the rheostat would dim the parking lights!

The year before the 4-fuse box was introduced cars had two in-line fuses for the parking lights, but this was one for the fronts and one for the rears.
Paul Hunt 2010

Thanks All,
I got the new block hooked up I think correctly. Look at the pic attached. When I took the old block off the the fender, I could see that imput 1 and 3 were connected.

It was very helfpul to learn the numbering sequence.

Take a look at the photo.

John


John Fraioli

This thread was discussed between 21/06/2010 and 23/06/2010

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