Clicking heater????????

I have 91 GMC 1/2t truck that clicks in the heater area when you start the truck and shut it off. This appears to be coming from the area around the blower motor at the passenger's feet. Each time it's starts clicking, it only does it for a minute or so and quits until you either turn it off or start the truck. Does anyone have any suggestions on what might be causing this problem?

door actuator need to be replaced
pull glove box at your left there is small black box mounted at heater duct with 4 wires on it

door actuator need to be replaced
pull glove box at your left there is small black box mounted at heater duct with 4 wires on it

The only plug I see on the left side has 5 wire 2 green, 2 blue & 1 black. Is this the same thing?

tell you what turn ign on and listn to which one clicking i reley forgot