Heater has quit working, how do i know if it is switch or fan or something else

Can you hear the front ac/heater fan? They use the same AC compressor so that should be okay. The fan switches fail quite often on those. That controls how much air is pushed by the fan for AC, heat and defrost. The switch is attached to the fan knob on the dash.

Most of the time when a heater blower quits working it is the blower switch that fails rather than the motor. Blower switch can be accessed in the dash panel.

if it does this on any fan speed it is most likely a bad blower motor, if it inly while on a certin speed such as full high or full low it could be the fan speed resistor located right near the fan motor, screwed into the fan housing

your fan speed regulator located on your heater core box is bad if its just one or some of the speeds. if the fan does not work at all its either a bad connection to your fan speed regulator or the fan motor has quit. out

it could be the fan motor, the resistors that control the speed or the switch as well as a loose wire

Hi
Check for bad connection at heater resistor or try tapping heater motor lightly
with ignition switch on and heater switch on. Could be heater switch connection.

No solution found as of yet.

Check the following fuses:
10 amp GAUGE under the dash, and the 40 amp HEATER under the hood.
If both fuses are good, I suspect that you may either have a bad fan switch or a bad heater fan motor. The switches are rare to fail, I would suspect the heater motor first. Please try this: Turn the key on; turn the fan switch to high. Look under & behind the glovebox, for the bottom of the heater fan motor. Round thing with 3 screws holding it to the heater box. Using a small hammer, or something that you can tap with, tap on the bottom of the heater fan motor. You just may jar the motor enough to make it run. If it comes back on, you may need to replace it at some point in the near future. Worked for me quite a few times. Try that, repost to me what happens. Hope this helps.