there is in fact a bulb, as mentioned. the way i got to mine in my '83 Sierra was to pull the dash bezel, then there are 4 screws that hold in the HVAC control panel, remove those...then you will be able to pull it out a LITTLE bit, which is normally enough room, if you tilt it right, to get to the bulb. just grab the socket, twist it (normally towards the passenger side of the truck, but be gentle) and pull it. the bulb will be on the passenger side of the HVAC control...opposite the fan switch...