Originally Posted by lolita18
I'm a senior woman with a 2000 Pontiac Bonneville that I love however the heat only works for the driver'* side and the passenger freezes with cold air at his/her feet and above the glove compartment vents. Any suggestions? I hesitate to visit dealership without some insight as to what'* going on. Would greatly appreciate any help.
Let me add to danthurs' answer that there is an actuators. If it'* a dual system with separate controls for the passenger side, then it has a separate actuator. The actuator is small electric motor unit that moves a vane inside the heater box to make more or less air from the heater path mix with air that bypasses the heater core. The motors burn out or the gears break.
The actuators are visible from under the dash. There are thin plastic shields or hush panels that come off with a couple of screws on the passenger side (and driver'* side). Then a mechanic can watch the actuators move their arm which is connected to the vanes inside the box. If they can visually see that an actuator is not move when the heater controls are changed then replacement is the probably solution.
This does not have to be at a dealer. A good mechanic who does this kind of interior work rather than mostly motor and brakes, etc., can do it and should be much cheaper. Even a talented backyard mechanic can change an actuator after they determine one is the problem; some parts are put in and designed to be quick changes anymore around the heater system.
The advantage to a dealer is they will diagnose it and replace it and probably get it right the first time if there is another cause.
Actuators have been failing occasionally on Buicks and Bonnevilles since they went electric controls instead of vacuum in 2000. So actuator is usually the first place to start.