There is a burning rubber smell coming from under the hood.

chances you have one of possible problems . your serp belt burned up because something seized.or a electrical short at the starter or fuse box. or in the fuse box the main fuse went. but not with smoke i would check the first two belt or short in the starter or alternater

Serpentine belts have an idler pulley and an automatic belt tensioner - either one of these could have gone bad and could cause the smoke. The idler pulley has a bearing inside that can seize, stopping the pulley from turning which would cause the belt to fray. The tensioner keeps the belt tight and when they go, the belt hangs loose, causing the belt to burn on the other components. The Alternator also runs on that belt, as well as the a/c compressor and other components, depending on the particulars of your car ( make, model, engine, accessories, etc.) and the main bearings can be bad there too. There are actually several key components running off the belt and, without being there, I cannot accurately diagnose the issue. I recommend you go to a reputable shop. The type of smell in the burning would guide me to what to check - there are many things that can cause these symptoms. If that mechanic only changed the belt but did not investigate the cause I personally would not go back there.
I'm sorry i couldn't offer anything more concrete to help - hopefully I've given you some directions to look!
Hope this helps!!

check your ac belts and pulleys. if there ok then possibly your ac compressor. your compressor not only holds freon but also oil it could be low and its burning your compressor

check your alternator,power steering or air conditioning belts, unless you picked up whilst driving from the road any plastic bag onto the exhaust pipe and stuck and melts on it.

Make sure you oil cap is on properly, look for oil underneath. Make sure emergy brake is not ceased and on!!

It sounds like the belt is slipping or maybe even the compressor is seized. Just check to see if the compressor is turning.

A burning rubber smell under the hood might be just that - consider having your accessory drive belt inspected, as it is possible that a bearing in one of the accessories (alternator, power steering pump, air conditioning compressor, etc.) or in the tensioner mechanism might be failing. This sort of fault will often cause that particular accessory bearing to spin less freely than the others, and as a result the belt continues to pass over the associated pulley at the same speed as the engine. Essentially, the result is similar to a car spinning its tires on dry pavement - and a similar 'burning rubber' odor is the friction and heat of the rubberized belt.

If the odor is more like burning oil than burning rubber, the rear valve cover gasket is situated in a place that results in dripping oil, even small and unnoticable amounts, onto the exhaust manifold that is directly underneath the valve cover.

These two items might be places to start your inquiry. Best of luck to you!

if the smell only comes on when the heater is on try pulling the blower motor mice like to build nests in the blower motor housing.

Check serpentine belt, the radidator hose , the air conditioner compressor and also the differential seal they common cause for rubber smell.

Check for any rubber part that can be in contact with exhaust system and inspect wirings looking for shorts.

Also ensure that the smell is not coming from a bad tyre, and check for oil leaks in your engine, burnt oil can be confused with rubbere smell.