The ticking sound that comes from under the dash near the passenger footwell in SSRs is due to a malfunctioning blend door motor that controls fresh and recirculated air. What is happening is that the geared motor broke a tooth and not the motor cannot go to the position selected but desperately tries to. There are actually 3 similar motors that control the AC and air temperature and movement in the SSR. One for heat, one for air direction and one for fresh or recirculated air. The recirc is the most common problem unit and it is located in the worst area.
To locate the motor you will need to remove the glovebox, and the plastic kick panel by the passenger foot area. With the system on and the ticking you can look at the upper area of the large AC unit just behind the glove box and watch the door snapping. The motor is at the very top of that open flapper area along the right hand side of the case. There are 2 bolts, both 5.5mm.
The motor is only about $45, part number Delco 1572794, but if you go to a dealer to install it will cost around the $2000 mark due to them removing the entire dash and AC unit. When I repair them I just get my hands in there with some small tools and remove it. It is not and easy task and you will likely say a lot of words you never knew you had in your vocabulary.
Some people decide to just disconnect the wires to the motor or just not move the switch to the error prone location.
Pictures are attached for reference. The drawing is 180 degrees opposite, as you look at it you are looking at it from the front of the engine. the part is item 33 that fails. You can see the blower unit 15 that is under the passenger feet area and also the flapping door, 27 that is behind the glove box.
The image below shows the dash somewhat taken apart. The red arrow to the right is pointing to the fresh air door, the motor is located to the right of that door against the wall of the truck.