The Fisher Body service manual has the power window information. According to it, the relay is mounted on the left side defrost duct in A body cars.
The relay will have three wires connected. A 12 ga orange/black, a 12 ga red/white and an 18 ga pink. The orange/black is the power source. It connects to a circuit breaker on the engine side of the firewall. The other terminal of the circuit breaker has a black wire that connects to the horn relay. The red/white takes the power from the relay to the window switches. The pink wire connects to the IGN terminal of the fuse block. When the ignition is on the pink wire sends power to the relay coil. If, the relay has power on the or/bk wire, the relay coil is good, the relay is grounded and the relay contacts are good you should have power on the rd/wh wire to the window switches.
Note: if the relay is mounted on plastic it will need a ground wire.
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