on your brake pedal lever,its a switch,easy to remove ,just unscrew bolt and disconnect wire.
no 84 and 85 swap out.
The 1984 Toyota pickup truck headlight relay switch can be found in the fuse box. The headlight relay switch will be at the top of the third column.
85 and some 86
185R14
no 84 and 85 change out.
check out ebay.
85 720
It is located on the right side below the gas cap.
Get your alternator tested at autozone,its free,and check your battery too.
under dash above gas pedal
Depends on which relay your talking about. Usually it tells the engine management computer that something is changing so that it can react accordingly.