The blower in the front of my '74 914 now works! - what makes the one in the engine compartment run?

advise appreciated thx.

Pulling up on the red heater control lever on the center console should activate it.

When I pull the red lever up it just opens the heater box flaps what starts the fan?

There's an electrical connection on the lever that closes when it's all the way up. Pull yours out and you'll see it.

You'll have a hard time pulling the lever out to check the electrical connection if you don't first detach the cables under the car that run to the two heater valves.

The heater lever with the red know in the console can come out without touching the heater flapper box cables.

The is a spade connector on the heater lever that grounds the relay.

Yes just pull the cover to confirm that you still have the switch and it's hooked up to a wire. IIRC the switch just grounds out the wire to complete the circuit.
There will also be a fuse I believe (educated guess) on the relay board supplying power to the fan.

Before pulling anything apart, confirm that you are indeed moving the lever all the way to the end of it's throw. The electrical connection happens at the very end.

Same fuse as fuel pump. On relay board in engine compartment. You can lift the lever up to check electric spade connection without loosening heater cables. Just done it repairing clutch tube.

Thanks I can't be pulling it up far enough, i have the same issue in my 912e. Duh