* Blower Motor Resistor: This is the most common culprit. The resistor regulates the fan speed. If it fails, the blower motor might not get power at all, regardless of the switch position. It's relatively inexpensive and easy to replace, usually located somewhere near the blower motor itself (often under the dash).
* Blower Motor: The motor itself could be faulty. It might be seized, have burned-out windings, or have a bad connection. This is more expensive to replace than the resistor.
* Fuse or Circuit Breaker: Check your fuse box (usually under the hood or inside the cabin) for a blown fuse related to the blower motor or HVAC system. There might also be a circuit breaker involved.
* Relay: While possible, a relay failure is less common than the resistor or motor. The relay acts as an electrical switch, controlled by the blower motor switch. A bad relay would prevent power from reaching the motor.
* Wiring: Damaged or corroded wiring between the switch, resistor, relay (if applicable), and blower motor can interrupt the circuit. Inspect the wiring for any obvious damage.
* Ground Connection: A poor ground connection can prevent the blower motor from receiving the necessary power. Check for a good, clean ground connection to the chassis.
Troubleshooting Steps:
1. Check the Fuse/Circuit Breaker: This is the easiest and cheapest thing to check first.
2. Inspect the Blower Motor Resistor: This is often the next most likely cause. Locate it and visually inspect it for any signs of damage (burn marks, etc.).
3. Test the Blower Motor: This requires some basic electrical testing (a multimeter) to see if it receives power and if it's functioning correctly.
4. Check the Relay (if applicable): You'll need to identify the HVAC relay in your fuse box diagram. You can test it by swapping it with a known good relay of the same type.
5. Check Wiring and Ground Connection: Visually inspect all wiring connected to the blower motor, resistor, and relay. Clean any corrosion and make sure all connections are secure. Pay close attention to the ground connection.
It's unlikely to be just a single relay problem; more often than not, it points to a blower motor resistor or the blower motor itself. Start with the simpler and cheaper options (fuse, resistor) before moving to more complex diagnostics. A repair manual specific to your 1993 Chevy S10 Blazer will be extremely helpful in locating components and understanding the wiring diagram.
