The horn on the MGB hasn't been working for awhile.
There are two horns.
This is the one on the passenger side.
This is the one on the driver's side.
They're mounted in series, electrically.
Spade connectors.
There's quite a bit of corrosion on the spade connectors.
Used a file to clean.
The DVOM battery went dead...
Used the small/cheap DVOM one for now. It works...
Also, one of the internal fuses was blown.
Had a spare, but need to get a 9V battery.
The horn is activated by grounding the circuit at the horn button.
The three spring/tabs that hold the horn button/pad in place are the ground path to the steering column which is bolted to the body, thus completing the circuit.
The three tabs where they contact the steering wheel/column are corroded also.
Cleaned the contact area of the three tabs with a coarse sand paper.
There's a spring loaded contact on the steering wheel/column that rests on this tab on the horn button. (forgot to take a picture of the small diameter, spring loaded contact rod).
Also cleaned the contact tab with some sand paper.
The 12V side of the horn circuit goes through this small fuse block in the passenger side of the engine compartment.
The purple wires on the right most fuse is the one that goes through the horn circuit.
I cleaned the contacts for the fuse and confirmed continuity with the DVOM.
The right most contact has been cleaned with sand paper.
After cleaning all the contacts at the horns, fuse block, the steering wheel horn button and steering wheel/column, the horn worked.
Fixed (for now, on a British car, not much electrical is fixed for very long...).