@flintknapper Good catch. There are two options in '98: 1) single air conditioner.... w/ binary switch and 2) dual air conditioner w/ trinary switch.
The trinary switch is quite spendy through Toyota ($100+) but can be had from Denso or aftermarket for much less. I don't know the procedure of...
@knewstance You could also check the connector under the AC sight glass. It should have 4 wires. If it only has 2 wires, then probably your 100 did not originally come with the condenser fan.