If you have vacuum-operated mode doors, look for a break in the vacuum hose feeding that system. Typically it's a small hard plastic hose running from a tee on the firewall to a small check valve, and from that, through the firewall. Most systems are designed to default to the defrost vents for safety. Your feet might freeze but your windshield will be clear.
Sunday, April 6th, 2014 AT 7:47 PM