I had this Problem once on an old Nissan. Once i changed the switch the problem continued. What resolved the issue was changing the ballast resistor located on the blower housing, Once i changed this resistor, all my speeds became available again.
check the blower motor resistor
Bad blower resistor?
Your heater coil is bad.
The most common cause of the heater blower being on high only is the blower resister failing. The second most common problem is the blower switch going bad.
most common problem is the blower resistor In the firewall on the passenger side of the truck is the blower motor speed resister coils, they burn out alot. I could not find one for my Dakota so I got one from a dodge caravan and I changed the wirring, that is the most likely problem
have you checked the fuse if so then you will need to replace the resistor for the blower hig and low dettings have you checked the fuse do you have 12 volts to blower if so then you will need to replace the resistor for the blower replace the blower motor
The most likely problem with the heater blower on your 2003 Sable is the blower resister. The resister can go bad and cause you to only have one speed.
blower resistor especially if its chrysler/jeep or blower switch
DON'T turn it on.
If a heater fan is not working on a Toyota RAV4, the problem might be with the blower motor resistor. The blower motor resistor is either on the firewall next to the heater motor or in the dash on the passenger side above the heater core.
While there are a variety of reasons your Lexus ES350 heater is not working, the most common 3 are a broken heater blower motor, a problem with the thermostat, or a failed heater blower motor resistor.
While there are a variety of reasons your Lexus ES350 heater is not working, the most common 3 are a broken heater blower motor, a problem with the thermostat, or a failed heater blower motor resistor.