Without Electronic Controls

PERFORM BEFORE BEGINNING SYSTEM DIAGNOSIS
1. If the HVAC Control Head is completely inoperative, check for an open in CKT 41 to the HVAC Control Head. Also check for poor connections at HVAC Control Head Connector C1 terminal "A1" and terminal "C12".
2. Check for missing or damaged connector seals at the Blower Motor Resistors, and High Blower Relay.
3. Check A/C Clutch Fuse if Blower Motor is inoperative.
^ Check for a broken (or partially broken) wire inside of the insulation which could cause system malfunction but prove "GOOD" in a continuity/voltage check with a system disconnected. These circuits may be intermittent or resistive when loaded, and if possible, should be checked by monitoring for a voltage drop with the system operational (under load).
^ Check for proper installation of aftermarket electronic equipment which may affect the integrity of other systems (Refer to General Troubleshooting Procedures). Diagnostic Aids
^ Refer to System Diagnosis. System Diagnosis