No heat on the floor in 2001 Chevy Silverado Z-71

I have a 2001 Chevy Silv. Z-71 that only puts out heat through the vents, but cold air comes in through the floor vents and is very weak through the defroster. Seems like the cold air only comes in the floor on the passenger side?

There are blend doors inside the heater box. These are probably operated by engine vacuum. I had the same problem on my 1978 Oldsmobile and found that I had accidentally knocked off a vacuum hose at the vacuum reservoir. I would begin by looking at the vacuum hoses under the hood and make certain that all are attached. If the problem goes deeper than this,I would recommend looking in a Chilton’s manual to see how difficult it is to service the vacuum actuator for the blend doors.

Remove your wiper arms then remove the cowl. Look on the passenger side and you will see a hole and you’ll notice a poor seal between the heater box and firewall. Reseal with silicone but be careful not to let silicone fall down onto the blower motor. This will cause an imbalance. Take a shop rag and place in the hole to prevent this but remember to remove the rag when you finish. You truck does not use vacuum controls to move the actuators as previously posted.