98 Lumina air comes thru defrost only and fans won't turn on

1998 chevy lumina 3.1
after replacing battery my car is now running hot, but if I turn on the heat it seems to fix problem, but heat and air only coming thru defrost vents, also the big fans by radiator are not coming on. Ever. The overheating prob worse in stop and go city traffic, my guess is on the frwy, the car gets enough air flowing thru it, but I usually leave the heat on 1 anyway, if the temp gauge goes up I turn heater up. Scared cuz Tx summer is coming and i'm going to bake if problem isn't fixed.

looked for obvious wear. Hoses etc, have recently replaced serpentine belt, harmonic balancer, then tensioner pulley, that was cuz car kept dying and when I was jumping it I noticed the serpentine belt was chewed up which led to other parts being replaced, never addressed battery dying all the time, but figured out the ignition switch is hinky and must be 'just so' or I get like a parasitic drain.

the fans won't turn on no matter what.