Olds/Sil a/c fan and rear blower problems

[kamal_elmasry]

Oldsmobile/Silhouette 1992 3.8L
a plastic bag sucked on the front radiator fan (a/c fan) and the plastic cover of the ground wire of this fan burnet according to the excess heat, I changed the ground wire and the motor of that fan, but I recognize that this fan doesn't work all the time I turn the a/c ON, it works just sometimes!! not all the time, Is this fan works through some kind of sensor?, or it should work all the time when the a/c is ON. The other radiator fan (from the motor side) is seams OK because it works when the motor temperature is 220F and works too directly when the a/c is turned ON. IS THERE A PROBLEM IN THE A/C (front) FAN???

Second thing, since that problem happened the inside blower fan (for the rear part of the van) doesn't work at all although the one of the front part is working nice. I checked all the fuses at the fuse box and even the relay behind the glove box. I do not know where is the location of this rear blower fan?, is it at the meddle part of the ceiling or where!! to check it? And what is the expected cause?
Please could anyone tell me what to do for the both issues.
Thanks a lot.

[kamal_elmasry]

The front fan is working when the temp. of the conditioned air is not enough OR when the rear a/c is ON.
Second thing, The rear blower is located at the left side of the car behind the driver chair, and the fault was in the switch itself.