If I remember right, it was the one one the sending-unit end, not the dashboard end, I didn't acutaly see it, I was stuck inside the cab monitoring the guages while the other half of the garage (my dad) was fiddling under the hood.
Apparently all he did was pull them apart, and then stick them back together again, and that was enough to "clean" them so they'd work again
The same problem was causing the horn not to work