I'd say start by checking Fuse #12 (the Arrow light gets +12V from another source).

Here's what's involved in OD control...

1) Fuse 11 (200) or 12 (700/900) supplies voltage to items #2, #3, and #4.

2) The Shifter button/switch turns the OD relay off and on

3) The OD relay controls the OD solenoid and the Upshift ("OD off") Arrow light (separate wires). When the Arrow light is ON, the OD relay and solenoid are OFF.

4) The OD solenoid allows OD engagement when ON, (this is the "default" OD relay/solenoid state at start-up)

If your shifter switch makes the Arrow light go on and off, then the OD relay is working (although it could still be failing to control the solenoid voltage due to burnt contact points).

If Arrow light doesn't go on and off, start with the Fuse. If fuse is OK, suspect OD relay, shifter switch, or wiring to the relay.

If Fuse 12 is blown, suspect the wiring from relay, going out and under the car to the solenoid.


--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.