why does the truck make a constant tick for a few minutes when turning on/off? on 1994 Chevrolet 1500 Pickup

when the key is turned on and off, a tick comes from the area under the dash on the passenger side. it lasts for about 2 minutes and then shuts off. it also ticks whenever you turn the a/c or heat on for the same amount of time. it does not affect the drive of the truck but is annoying and embarrassing.

Asked by for the 1994 Chevrolet 1500 Pickup
1 answer
My truck also 94 chevy does same thing, co-workers said it was a chevy anti-theft device to make thieves think it had a timer for a bomb, they bought toyota trucks- don't do such silly things.