Climate Control Symptom Troubleshooting Index
Symptom
Diagnostic procedure
Also check for
Blower, heater controls, and A/C do not work
Voice communication does not work
HVAC display is not indicated
Both fans do not run at low speed with the A/C on (but the A/C compressor runs with the A/C on)
  • Blown fuse No. 3−6 (MAIN FAN MTR) (30 A) in the under-hood fuse/relay box
  • Faulty radiator fan relay
  • Faulty fan control relay in the relay circuit board
  • Cleanliness and tightness of all terminals
The A/C condenser fan does not run at high speed (but both fans run at low speed and the A/C compressor operates with the A/C on)
  • Blown fuse No. 5 (20 A) in the under-hood fuse/relay box
  • Faulty A/C condenser fan relay in the relay circuit board
  • Cleanliness and tightness of all terminals
Both fans do not run at high speed with the A/C on (but both fans run at low speed and the A/C compressor operates with the A/C on)
A/C pressure sensor troubleshooting: A/C pressure sensor circuit low voltage, R20A3 engine model, K24Z3 engine model, A/C pressure sensor circuit high voltage, R20A3 engine model, K24Z3 engine model
The A/C compressor clutch does not engage (but both fans run with the A/C on)
  • Blown fuse No. 20 (7.5 A) in the under-hood fuse/relay box
  • Faulty A/C compressor clutch relay
  • Blower motor operation
  • Cleanliness and tightness of all terminals
A/C system does not come on (both fans and the A/C compressor do not work); heater is OK
A/C signal circuit troubleshooting A/C pressure sensor troubleshooting: A/C pressure sensor circuit low voltage, R20A3 engine model, K24Z3 engine model, A/C pressure sensor circuit high voltage, R20A3 engine model, K24Z3 engine model
Blower fan runs slower than expected in cold weather
ECT troubleshooting: ECT sensor 2 circuit low voltage, R20A3 engine model, K24Z3 engine model, high voltage, R20A3 engine model, K24Z3 engine model
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 climate control unit or the vehicle
Troubleshoot the DLC circuit, R20A3 engine model, K24Z3 engine model
Insufficient heating
1.
2.
3.
4.
5.
6.
7.
Check the coolant temperature
Check the blower motor unit for obstructions
Check for air leaks around the ducts and vents
Check the inlet hose temperature
  • If it is COLD, check for restrictions in the hose, a damaged or leaking thermostat, and a damaged or leaking water pump.
  • If it is HOT, check for restrictions in the heater core. Back flush the heater core using standard commercially available equipment, or replace the heater core.
Damaged cylinder head gasket