What could be causing my car to smell like gas when I use the air condition or heat?

Usually a gas smell through the climate system indicates an EVAP system malfunction. Usually these are not user serviceable. Take the car to a shop to have it sorted out.

Please re list the question with the year, make, model and engine size in the question. VW's take their cabin air from the engine compartment which means if you smell gas it is leaking some where under the hood, which is bad but you can press the button to recirculate the air instead of bringing in fresh air and the gas smell will go away. Some cars have a gas tank sealed door in the bottom of the trunk below or above the spare tire. If the seal is broken then it can release gas fumes which is bad. Or you could of accidentally poured gas into your trunk drainage canals while putting the gas machine gun back in the machine which means you just need to clean up the gas which will be on the out side or maybe with worn weather seals it could be inside. There are a lot of reasons you can smell gas and most of them are hazardous to your health, so tell us what your car is or take it somewhere to get looked at. Good luck!

Are you smelling "raw" gas, or the smell of a hot engine? Both are similar in smell. If you have a gas leak you will smell it all the time regardless if you use the heater/ac or not. You say you only smell it when the heater/ac is on, then I would look for a broken housing, around your heater/ac under the hood of the car. If there is a hole, or something missing, the fan will draw in the air from around the engine giving you a "gas" or hot engine smell.

You have a leak in the fuel system. Possibly a leaking fuel injector. Very dangerous fire hazard. Do not park this vehicle in a garage or near any building just in case it catches fire.

Do not use this vehicle again until it has been looked at by a reputable independent mechanic.

That doesn't sound good...there should never be a smell of gasoline....get it to a mech ASAP and have them check for gas leaks.

Open the hood Jonathan. What do you see?