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Bench Checking Overdrive & Power Seat Relays The overdrive relay can be bench checked using a external voltage source. The large clips in this photo are from a portable jump starter. The large red clip (Pos) is connected to the Ignition terminal of the solenoid. The large black clip (Negative) is connected to the case mount bracket of the relay. Next connect a small jumper from the case or large black ground clip to the left terminal marked TH SW (throttle switch) you will hear the relay click closing the points. When the points close, voltage is directed to the solenoid terminal located on the lower right side of the relay. The SOL terminal provides voltage to the overdrive solenoid located on the overdrive section of the transmission. The power seat relay can be checked using the same method. The power seat relay does not have a fuse. The large red clip from the power source should be connected to the center terminal of the power seat relay. The other connection will be the same as for the overdrive relay.