HEATER SYSTEM TROUBLESHOOTING
| NOTE: | This is GENERAL information. This article is not intended to be specific to any unique situation or individual vehicle configuration. The purpose of this Troubleshooting information is to provide a list of common causes to problem symptoms. For model-specific Troubleshooting, refer to SUBJECT, DIAGNOSTIC, or TESTING articles available in the section(s) you are accessing. |
BASIC HEATER SYSTEM TROUBLESHOOTING CHART
| CONDITION | POSSIBLE CAUSE |
|---|---|
| Insufficient, Erratic, or No Heat | Low Coolant Level |
| ..... | Incorrect thermostat. |
| ..... | Restricted coolant flow through core. |
| ..... | Heater hoses plugged. |
| ..... | Misadjusted control cable. |
| ..... | Sticking heater control valve. |
| ..... | Vacuum hose leaking. |
| ..... | Vacuum hose blocked. |
| ..... | Vacuum motors inoperative. |
| ..... | Blocked air inlet. |
| ..... | Inoperative heater blower motor. |
| ..... | Oil residue on heater core fins. |
| ..... | Dirt on heater core fins. |
| Too Much Heat | Improperly adjusted cables. |
| ..... | Sticking heater control valve. |
| ..... | No vacuum to heater control valve. |
| ..... | Temperature door stuck open. |
| Air Flow Changes During Acceleration | Vacuum system leak. |
| ..... | Bad check valve or reservoir. |
| Air From Defroster At All Times | Vacuum system leak. |
| ..... | Improperly adjusted control cables. |
| ..... | Inoperative vacuum motor. |
| Blower Does Not Operate Correctly | Blown fuse. |
| ..... | Blower motor windings open. |
| ..... | Resistors burned out. |
| ..... | Motor ground connection loose. |
| ..... | Wiring harness connections loose. |
| ..... | Blower motor switch inoperative. |
| ..... | Blower relay inoperative. |
| ..... | Fan binding or foreign object in housing. |
| ..... | Fan blades broken or bent. |
