Heater/ac fan motor will run at high speed.1 could it be the switch or is there a controler on the motor 2 the motor is acessable how

The blower motor relay is energized when the Blower Motor Control is set to the High position. This removes the blower motor resistors from the circuit and battery voltage is then applied directly from the HVAC BLO fuse (RH IP Accessory Wiring Junction Block) to the blower motor though the relay switch contacts. The blower motor then runs at high speed.

HVAC Blower Controls Circuit Description
The blower motor is a variable speed motor. The motor operates at a higher rate when voltage is increased to the maximum level.
The blower motor resistors reduce the voltage supplied from the A/C FAN fuse (LH IP Accessory Wiring Junction Block) when the blower control is set at low and medium speeds (speeds 1-4). The blower motor relay is energized when the Blower Motor Control is set to the High position. This removes the blower motor resistors from the circuit and battery voltage is then applied directly from the HVAC BLO fuse (RH IP Accessory Wiring Junction Block) to the blower motor though the relay switch contacts. The blower motor then runs at high speed.

Sounds like your fan switch could be shorted out

the cab heater fan?, there can be 4 fans on some cars.
front condenser, 2 on rad, and 1 in cab heater box.
the cab fan? does it fail on high too?
it has a switch, (marked fan speed)
the switch is bad ,if low speed are dead. and high are good.
or wiring to it , the motor or the fuse.
even a cracked fuse, change the fan fuse to a new fuse.

you probably need new control switch.

Hello,
You may want to try your fan on all speeds. If it will work on high, you have a bad resistor for the fan motor. ( high speed doesn't go through the resistor ).
If it doesn't work on any speed, I would check the following;
1. Make sure the fuse isn't blown for the fan blower motor.
2. Check, or have checked the wires between the fan control switch and the fan blower motor.
3. Have the fan control switch checked.
4. Have the fan blower motor checked.

I hope this helps you.

THE BLOWER MOTOR RESISTOR FAULTY IF YOU HAVE ONLY 1 FAN SPEED ALSO AC AND HTR CONTROL SWITCH BAD.WATER LEAK UNDER GLOVE BOX COULD BE THE HEATER CORE LEAKING IF LEAKING ALL THE TIME WHEN THERE IS NO RAIN.

Good Evening, If I am translating this properly your fan only works on the high setting? And the other settings do not change the speed? If this is correct respond back and I will help as much as possible.

check the switch,s at the back of the ac control in the dash, if you ac has an automatic temp gauge that also my be the problem.

Check the heater control switch,,,,,and the number of wires at the heater motor....Some motors have more than one winding...in which case there will be three or more wires going into motor..there can be burnout in those windings and will require a new motor....check the plug which attaches to the motor....can be bad connection...or at the switch.....but if there is only two wires....then the heater switch uses resistors to slow down the different speeds...and direct connection for high speed....and the problem is definitely the switch...

Check or have checked the blower motor resistor. This is usually how they act.