Just replaced bad battery in car three days ago for my kid. Got a ride home from him tonight and no heat in the vehicle. Don't know if the battery had anything to do with it or maybe a thermostat problem. Any ideas?

please put your year and your model in your sig

and does your car have electronic climate controll???...if so im betting on the Air mix door actuator snapped its gear

Is the coolant tempurature gauge showing normal operating temperature?

Check coolant level in radiator when cold. If low, find out why. Could be other problems. Top up radiator and overflow tank and bleed engine of air. Feel heater hoses when car is warmed up, if both are hot, the problem is in the ducting, usually the air-mix actuator, a little motor that opens the flap to allow air to flow through the heater core. If one hose is hot, and one cold, it is restricted coolant flow through the heater core- replace heater core.

This wouldn't be the first time a battery change or battery disconnect resulted in a craked gear in the airmix actuator. It has occured often enough that we have had discussions about why this happens, but have never pin-pointed the relationship.

Check the things mentioned above and if need be, we can guide you through the airmix actuator fixes.