fan/vent control lights on 73

There are 4 light receptacles in the fan/defrost control. The 2 on top are for the fan and the 2 on the bottom are for the vent controls. I've only got a 3 bulb harness, missing the light that should illuminate the red fan light. Is this normal on a 73 , no light in the red fan light only the blue one?

Dave, I think the extra light hole was for gas heater application.

Thanks Ed, Since I replaced my ignition switch, I've been tidying up everything under the dash. I must stop as this is just looking for trouble.