blower moter coil windings shorted, motor spinning too slow than normal (increase current draw), short circuit in wiring, excessive amp or current draw in blower circuit than what is protected by amp rating fuse for that circuit. maybe even having too many loads (electrical devices on at once) especially if all these devices are connected in a parallel circuit and power is bridged.
Heater motor switch and or the connection at the switch is melted. Also check connections at the blower motor and blower motor resistor for melt down damage.
If you have no blower speeds at all check the fuse, then check the blower motor switch and electrical plug for a melt down situation, then check the blower motor itself.
Connections get corroded and loose, causing resistance which causes the wires to heat up and melt.
Inspect the backside of the blower speed switch. Look for an overheated, melted plastic connector. Loose connections causes resistance, resistance causes heat, heat causes melt down. Look for melted connections at the blower motor and resistor also.
The blower motor is going bad and drawing too much current.The blower motor is going bad and drawing too much current.
Excessive curent draw, usally a weak blower motor.
Blower motor located at the passenger side under the dash. Probably the blower motor but you need to check the blower motor resistor and the plug to the resistor. A common cause is the plug tends to melt & short out.
Defrost uses the a/c, if it doesn't smell the same with a/c only on. The smell is coming from the blower motor. Bmw's for example have a problem where the blower blade contacts the plastic housing and causes it to rub/melt.
by the blower motor there is a resistor connection, you will find it melted the blower motor is bad. it draws to much power causing the connection to get hot and melt and burn. you will have to change the connector and the blower motor. the blower is still working but its drawing to much power, the motor windings are shorted out inside. disconnect the connector from the resistor and you will see it.
see nhtsa action no ea1003 about this problem.
Yes, you can melt the heat exchanger and start a fire that way
To expound on this. What happens is resistance builds in the circuitry behind the switch and overheats the metallic elements inside the switch, causing the plastic in the switch to melt. This causes sporadic operation at any speed or only at certain speeds, and the owner may have to work with the fan speed switch itself to make it work. The underlying problems that CAUSES the resistance may be several things, but the root of the problem is usually the blower motor going bad. This builds resistance inside the blower motor, which also builds in the circuit. Replacing the fanspeed switch will only mask the problem and burn out the new switch. The proper fix for this instance is the motor. EDIT: I have researched this and found that it seems to be the resistor that causes the majority of these problems, rather than the blower motor. Do know, however, that either of these can cause this problem.