Where should I look first for no hot air in heat mode. Fan runs. 1997 iroc 5.7. Thx.

 

First check your coolant level. An empty heater core can't transmit heat.

 

97 ?
after coolant level is checked, warmup the engine.
feel the heater hoses before and after the control valve to determine where the coolant is stopped.
if warm to heater core might be a mode door issue.

 

Will do. I hear switch cycle when I turn key to run and switch fan from med. to high. Thx

 

my car was doing this. turned out that at some point the heater core started leaking so they moved the hoses around any bypassed the heater core. so no heat until i replaced it.

 

Your thermostat may be stuck open. What does your engine temperature read? My 89 convertible has a stuck open thermostat right now. I drove it 30 miles to put it in storage for the winter a couple months ago and my engine temp barely registered anything on the gauge and I had ZERO heat. I thought I was gonna freeze, lol.

 

Do you hear the temp door moving when you slide the temp control from warm to cold?