Air condition model quite easy .
1. remove complete unit by putting two thin cards at eath side of heater controls to unclip
2. Remove two screws at rear and replace bulbs .
Remove the heater control valve and replace it.
You can't just replace the lights you would have to replace the whole control cluster.
The heater control valve on your Pontiac Grand Prix is located behind the kick plate, on the passenger side of the passenger compartment. The heater control valve is near the heater core box.
Behind the glove box.
behind you glove box
There is one bulb for the manual heater control. It is located behind the fan control knob. Remove the knob take a piece of vacuum or windshield washer hose and remove the bulb. Install in reverse order of removal. The bulb is a 194 bulb.
You take it to a AutoTech.
It is located behind the bulkhead, accessible from the engine bay.
Behind the intake plenum on the passenger side.
To change the heater core in a 87 ford f150 is easy. Just remove the glove box and then behind it there is 7 bolts. After you remove the 7 bolts then just remove the cover and behind it is the heater core. By far the easiest heater core I ever changed.
The most likely reason that the heater control won't change the air flow is that the cable that moves the diverter valve has broken and will need to be replaced.
The heater control valve (temp blend door) is located behind the dash assembly. The dash assembly has to come out to gain access to it.