Over time debris and other things can collect near the heater core, its possible that something small and plastic has fallen down through the defrost vents and gets hot when the vehicle is running. You may need to disassemble the heater and remove the items and perhaps vacuum it out.
a burnt rubber ball in the cardorater
The smell of burnt rubber is often described as similar to the scent of a tire fire or a hot rubber material.
Acrid
probably being over used and the rubber inside is burning and melting....
You can try wiping the rubber weights with a damp cloth soaked in a vinegar or lemon juice solution to neutralize the smell. Alternatively, you can also try placing the weights outside in a well-ventilated area to air out and dissipate the smell over time. If the smell persists, you may need to replace the rubber weights.
Where ?on what? Mostly on a belt driving something
A burnt rubber smell in conjunction with a draining car battery could indicate several issues. It might be due to a malfunctioning alternator, which can cause the battery to overcharge and produce heat, leading to a burnt rubber smell from the wiring or insulation. Additionally, a short circuit or damaged wiring could generate heat and the burnt rubber odor while draining the battery. It's advisable to have the car inspected by a professional to diagnose and resolve the issue safely.
burning rubber
The distinct and memorable smell of burnt rubber is due to the release of chemical compounds called volatile organic compounds (VOCs) when rubber is heated to high temperatures. These VOCs create a unique scent that is easily recognizable and can trigger strong memories or associations in individuals.
The smell of burnt hair is often described as a mix of sulfur, chemicals, and a strong, unpleasant odor. It can be likened to the smell of burnt rubber or a pungent, acrid scent. The odor is distinct and easily recognizable, lingering in the air long after the burning has stopped.
sounds like your air conditioner compressor is bad.
Friction from excessive braking causes heat, thus the lubricant on brakes release this burnt smell.