Heater motor only works on the two highest setting

Sounds like the blower motor speed control switch may be defective or you have burned wiring or connectors, pull the blower switch out of the dash and examine it for signs of overheating and a burnt smell, check the connector at the blower motor as well for same things, repair as needed, also I would replace the blower motor as well.

Most common repair is replacing the heater motor blower resistor located near the heater motor

there is a blower motor resistor in the heater box that is causing your issue.

no the blower switch on the dash board is at fault the high blower speed works off the relay only which is ok

change heater control switch common problem, ive had to change mine twice

Its the Blower Resistor....If it was the switch, it probably wouldn't work at all....But the Resistor will give you those symptoms, of working on high med or low

Hi. This will be the result of a failed resistor switch. the switch controls the current level sent to the blower motor. Once replaced, the motor will operate at your desired rate. This switch is an integrated part of the AC/Heater control cluster, that is mounted in your dash. You will need to remove the trim, and cluster assembly to expose the damaged switch.

heater blower motor risister most likely cause. should be under dash near heater motor.

Is there power at the Relay on highest setting if not replace bower switch 95% sure switch is bad

this is caused by the blower motor speed control resistor being defective, this part is located near the blower motor.