MGB & GT Forum

Never gaze too long at your engine bay wiring.

On my 79B, there is a starter relay and an ignition relay. The starter relay is located on the fender wall aft of the fuse box-normal location.

Upon closer examination, I found a BLUE wire (where the BROWN goes on the starter relay terminal) which connects to the "relay looking" "stacked" boxes in the photo. The BLUE wire is actually fed by a yellow wire plugged into the bottom of the lower cube and then goes to a BROWN. So, it's eventually feeding power to the starter relay where it then terminates.

The boxes I can't identify (which looks like a relay plugged into a relay socket) have a ground and a white wire also attached, plus the yellow, although I'm not convinced that the WHITE is an actual WHITE as it looks to be a color shade "off". It disappears into a stock harness!

There are a couple of other wires around this (red and brown) but they're unrelated.

BTW, this car uses the original style electronic ignition which was replaced and looks to have been installed professional....or just neatly.

Anyone ever seen this? Eventually I'll forget about it but it's just bugging me now Just clueless as to why this exists.

Advance Auto Wire schematics:

http://www.advanceautowire.com/mgb.pdf

Nothing remotely like that on my '78. I think you can maybe ignore those wire colors since blue wires are for headlamps and yellow for overdrive. Sounds like a PO wired something just using the color wire he had on hand.

I suppose you could unplug the wires from that relay and wire the starter relay per the factory diagram, then see what doesn't work.

My '79 has dealer installed Bosch driving lights and the relay is in that same location.
Similar wires too..but the relay does have a BOSCH trademark on it.
The Slate/Purple and Slate/Yellow wires with blue tape run over to the anti-run on valve (first pic).

Also if the same as my '79 the old wiring and plug for the OPUS system should be hanging in there. You can see the old plastic plug laying next to the coil in my second pic. Might be the white wire you are finding.

The relay plugs into a socket. The socket comes with a wire pigtail that does not match our harness colors. It does look like it is eventually matched up correctly. The previous owner must have to lengthen the wires and used whatever he had. I would correct the extra wires and crip new lugs on them while eliminating the socket and wires.

Thanks Gentlemen. I guess I should have been able to figure this one out; still not sure what that relay is for although it does say Bosch on it so probably some accessory that sounded like a good idea to someone.

Ignoring the white wire, I'm just gonna route the Brown from the harness to the other relays and remove Blue and Yellow. Less is better. I'm thinking of keeping this car and if I do, my goal will be to simplify all things engine bay, including a move to SU's and deleting all components uninvolved in making the car go forward.

Cheers!

DD

If you want to know what the relay serves, unplug it. Something will stop working,


GMc

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