* Blown Fuse: This is the *first* thing to check. Locate the fuse box (usually under the hood or under the dash) and find the fuse(s) related to the blower motor. A blown fuse is a simple and inexpensive fix.
* Blower Motor Resistor: This component regulates the blower speed. If it fails completely, the blower won't work at any speed. It's a common point of failure and relatively easy to replace, although location varies by vehicle. You'll need to consult your repair manual or search online for its location in your specific 1990 Toyota pickup model.
* Blower Motor: The motor itself could be faulty. This is more expensive to replace than a fuse or resistor, but if the other components are good, it's a likely candidate. Testing the motor requires some electrical knowledge and tools.
* Wiring Issues: A broken or corroded wire in the circuit supplying power to the blower motor could interrupt the power completely. This requires tracing the wiring harness, which can be time-consuming. Look for broken insulation, corrosion at connections, or pinched wires.
* Switch Malfunction: While less likely to cause a complete failure across all speeds (usually you'd see some speeds working), a completely failed blower motor switch could be the root cause.
* Relay Failure (less likely): Some vehicles use a relay to control the blower motor. A failed relay would prevent power from reaching the motor.
Troubleshooting Steps:
1. Check the fuses: This is the easiest and quickest check.
2. Inspect the blower motor resistor: Locate it (consult a repair manual), and visually inspect it for signs of damage. If possible, test its continuity with a multimeter.
3. Check for power at the blower motor: Use a multimeter to check for power at the motor's terminals. You'll need a wiring diagram to identify the correct wires. If there's no power, trace the wiring back towards the switch and fuse box.
4. Inspect the blower motor itself: If power is reaching the motor but it isn't working, the motor itself may be faulty.
5. Test the blower switch: This might require some electrical testing to confirm proper functionality.
A repair manual specific to your 1990 Toyota pickup model will be invaluable in this process, providing wiring diagrams and component locations. You can find these online or at auto parts stores. If you're not comfortable working with electricity, it's best to take your truck to a qualified mechanic.
