Things to check:
Coolant level
Heat and AC fuses
Vacume leaks
Actual operating tempurature of the engine.
you can die in a hot car by getting heat stroke
Friction produces heat. Oil lubricates the engine and reduces friction thus reducing heat.
Solenoid is getting hot from heat transfer. Wire in a remote solenoid.
The heater in your car uses waste heat from the engine to heat the car. When the engine is not running there is no heat to distribute.
If you mean engine coolant is getting into the car, the heater core is leaking coolant causing the coolant level to drop and that causes the engine to over heat.
While there are many reasons for non heat production, the primary reason you aren't getting heat in your 1998 Volvo 240 is the simple fact that Volvo stopped producing the car in 1993.
It shields the rest of the car from the heat of the exhaust or radiator .
No! A car backfires because unburned fuel is getting to the muffler. The heat of the exhause system causes the fuel to combust, thus a backfire. A bad alternator will just not charge your car battery.
A car engine is a heat engine, but there are various types of heat engines outside the realm of car and truck engines.
Car not blowing air or heat
The heat will also work when the car is turned on, but not moving. It uses heat from the engine.
Like a greenhouse, a car with closed doors and windows is a closed space. Heat trapped inside a closed car cannot get out fast. Although the sunlight heats up both inside and outside of a car at about the same rate, the heat getting inside the car is trapped in a closed space. It cannot get away as fast as the heat outside, where it's an open space and heat can lose freely. Therefore, the heat inside accumulates much faster than the heat does outside, which is why the inside of a car is hotter than the outdoor temp on a summer day.