Heating Symptom Troubleshooting

Symptom
Diagnostic procedure
Also check for
Blower and heater controls do not work
Both fans do not run at low speed
  • Blown fuse No. 18 (20 A) in the under-hood fuse/relay box, and No. 36 (10 A) in the under-dash fuse/relay box
  • Cleanliness and tightness of all terminals
The A/C condenser fan does not run at high speed (but both fans run at low speed)
  • Blown fuse No. 15 (20 A) and No. 20 (7.5 A) in the under-hood fuse/relay box
  • Cleanliness and tightness of all terminals
Blower fan runs slower than expected in cold weather
NOTE: It is normal for the blower to run slowly until the engine coolant temperature begins to rise. If the blower continues to run slowly for an abnormal length of time, continue to troubleshoot the problem.
HDS does not communicate with the heater control unit or the vehicle