A/C fan motor only works on high. Need how to info to replace switch for fan motor control

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.

On any other vehicle it sounds like the blower fan switch.
The fan switch provides power or ground to the resistor and there would be a high speed blower relay to bypass the resistor.
But in your case the fan switch is part of the controller.
I don't have a diagram for a 92 but the 94 model shows relays for low medium and high speeds. Each relay gets power from a fuseable link. The high relay gets power thru the low relay if the low relay is not engaged.
If you have the model with 3 relays you may need to check them.

hi,

found this for you..

https://www.2carpros.com/questions/gmc-jimmy-1996-gmc-jimmy-heater-blower-motor-not-working

Hi!!
When the Blower Motor Resistor (controls blower speeds) goes bad, the blower motor works only on HIGH SPEED. REPLACE IT.
BLOWER MOTOR RESISTOR Removal & Installation

• Disconnect negative battery cable.
• Remove right lower instrument panel insulator panel.
• Disconnect blower resistor connector located behind right side of dash.
• Remove blower resistor screws and blower resistor.

To install, reverse removal procedure
Good Luck!! A HELPFUL - 4 THUMBS - rating for this solution would be greatly appreciated. Thank you for using FixYa!!

this problem is not caused by the switch, it is caused by a defective blower motor speed control resistor, the resistor is located near the blower motor.

high amperage draw. do all the speeds work? if so replace the motor. if not replace the resistor and the motor.

the blower fan is controlled by a module that communicates through data control info from the control panel to the fan control module. in your case the module is attached to the fan motor as one unit. if you unplug the fan you will find three wires in the connector. two thick black and red and one thinner wire, the thin wire is data. you will need to replace the whole fan unit to fix speeds.

Have you tested/replaced fan motor resistor yet? Most common problem when fan only runs on high, is the resistor.

That usually means the circuit board for the fan motor is Burt out big job prob to replace dealer may be.

Check the relais module located inside under the rh side of the heather box you can see the connector most of them need to be replaced as they burn out you may need to replace the blower motor as well,high amp draw caused by faulty bearings will overload the blower motor controller