If you have 12 volts at the blower, And the blower runs when it is straight wired. The blower switch runs through a resistor that allows the blower to run in low, medium-low, medium-high. Find and check this resistor. Most of the time it is located on the passenger side of the firewall.
To test the blower motor resistor, unplug the resistor connector. Each blower motor switch input terminal on the resistor must have continuity to the resistor output terminal, which is connected to the circuit going to the blower motor. If the blower motor resistor continuity does not check OK, replace the faulty resistor.You need a multimeter to test the resistor block and there should be continuity between all terminals.
Blown fuse, defective blower motor resistor pack, blower motor, or blower motor switch. This happened to me and I found a connector at the fan motor had fried. I changed the connector and it worked great.
Pull out the lock on the blower motor resistor wire harness connector to unlock the connector latch . Depress the latch on the blower motor resistor wire harness connector and disconnect the connector from the resistor. Remove the two screws that secure the blower motor resistor block to the HVAC housing. Remove the resistor block from the HVAC housing............
Under the hood. In the blower motor harness connector.
You have to access the motor to test it but it probably is bad. The brushes in the botor hangup a lot and when this happens it quits.
Try wiggling the electrical connector at the blower resistor. If wiggling this connector makes the blower go on and off, turn everything off and replace the connector before anything catches fire and burns the truck down.Next, when the blower is not working, set the fan speed to hi and try gently tapping the blower with a hammer. It that makes the blower come on the blower motor is bad and should be replaced. Also, use a test light or voltmeter to check for voltage across the two wires at the blower motor when it won't work. If voltage is present but motor won't work, motor is bad.
The blower motor resistor is located just above the blower motor under the hood. It should have an electrical connector plugged into it and some screws holding it in place.
There is a removeable panel below the glovebox. It is in front of the blower motor against the firewall. It has a wire connector from the loom and then it plugs into the blower motor
should be the connector in the ac housing closest to the blower motor
by the blower motor there is a resistor connection, you will find it melted the blower motor is bad. it draws to much power causing the connection to get hot and melt and burn. you will have to change the connector and the blower motor. the blower is still working but its drawing to much power, the motor windings are shorted out inside. disconnect the connector from the resistor and you will see it.
Connect the blower motor directly to 12 volts DC. If it runs it is good.
The blower motor resistor is above the passenger side close-out panel, below the glove compartment and towards the firewall. There will be a wiring harness leading from it to the blower motor and another harness leading into it. The harness leading into it will have a 4-wire connector and the harness leading to the blower motor will have a 2-wire connector.