Try this, locate the fan switch that is mounted in the intake manifold. Will have a GRN/YEL wire going to it. Disconnect the connector from the switch and get a piece of wire to run from the connector terminal to the engine (to ground that wire).
Key-on, engine-off, use the wire to connect the GRN/YEL wire terminal to the engine someplace. This should run the fan in high speed mode. If it doesn't, does the relay at least click? If so then the fusible link at the starter is likely bad.
If the relay isn't clicking then check the RLYS fuse in the fuse block (top of block).
If that fuse is OK then there is a wiring issue such as a cut or broken wire.
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