Heater System Troubleshoot - Low or no heat, blower not working and more

General Automotive Repair

The general trouble shooting information lists common vehicle symptons with possible solutions and is not for any particular vehicle make and model. For repair info specifically for your make and model please view the main directory.

Low, Erratic, or No Heat

• Low Coolant Level
• Incorrect or faulty 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

• 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.

General Automotive Repair

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