I have cold air coming out of the drivers side vents and ducts and warm air coming out of the passenger side. My mechanic said I needed to replace the climate control unit but that didn't solve the problem. I purchased a used unit from eBay and figured it would work. One of my friends a Pontiac afficianado suggested that it might be a vacuum line problem to the vent unit (??). Any help would be appreciated as the weather is turning cold.

Welcome. Would you add your year, and model to your profile. That will help us provide you with proper information, and you won't have to post it each time.

By your description, it sounds as if you may have the automatic dual climate control system. If so, you could have a faulty driver'* side air mix actuator. On the 2000+*, the system is electronically controlled, not with vacuum lines.

I have a 2002 SLE and it does have the dual climate control system. The unit that is in there was one I purchased from a wrecker on eBay. Is this a common problem? It had the same or similar problem with the original unit in and that'* why I changed them out. Thanks for your response.

What exactly did you replace? The "climate control unit" makes me think of the controller...that contains the ***** for the settings, and the display. There is an actuator for each side that determines the temperature. This link shows their locations.
HVAC Actuators

Ok, I replaced the controller. Are the actuators inside the car or in the engine compartment? How difficult a replacement is it? Any idea of cost for each actuator? Thanks again.

The actuators are inside the car. I believe the driver'* side one is roughly near the center of the dash tucked up underneath. This is the replacement procedure. New, they'd probably run in the area of $100. You may want to check GM Parts Direct, or Rock Auto for new ones, or check with Ed Morad by sending a private message to GTPMorad to see if he has a good used one.

Edit - It would help if I added the link. Air Temperature Actuator Replacement - Left

Hi!
I've got the same issue with my 2000 Bone with the addition that hot air comes out the rear console vents as well as the passenger side vents (with the A/C on)...is there another actuator for the rear seat or is it controlled by the passenger side?

Thanks in advance!

2000 Black Bone - gradually disintegrating electronically.

I have a similar problem with heating system except I get heat on the driver'* side but not on the passenger side. The vents above and below the glove compartment give cold air while the driver'* side does provide hot air. Any suggestions?