During the winter time, if your Guests are getting cold air blowing on them with the heat turns off in your dining room, then your dining room HVAC diffusers most likely need to be adjusted so that the air doesn't blow directly down. The attached memo gives details on how to make this adjustment. If you need more assistance, please contact your FM.
The colder air is coming from the outside due to the requirement that the HVAC fans have to stay on during business hours even when the HVAC is not actually heating. This requirement is for two reasons: 1) to keep fresh air circulating for your Guests and 2) to maintain positive air pressure in your restaurant.
Another possibility is that the economizers on your HVAC units are open too much and bringing in more outside air than needed. If you believe that this is the case, call your HVAC technician out and have them inspect the economizers to ensure that they are in working order, then make any needed adjustments.
See attached instructions.