In the a/c system where is the location of the fuse, relay, and ecm

Probably check the bulb, - there is a circuit from the control switch on dash that goes to the bulb-- it should be lit whenever the switch is turned on to A/C. Unless it is one that goes on and off with the compressor as it runs (not common), - but if it works this way,-- it has to be on the compressor side of the thermostat to go on and off with the compressor!

If you have the power to the bulb, and the bulb is good, then check your ground-- can't complete circut from bulb to battery without having ground working!

I assume you mean the on-off indicator, -- not the backlighting for the panel which goes on with dash lights!