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Troubleshooting
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Blower Fan Works On High Speed Only
Blower Fan Motor Works On High Only
All cars are designed with a blower fan motor that pushes air through the venting
system. This air is processed by a series of vents to direct the air to various
positions ex: heater, air conditioner and defrost modes. Most blower motors are
power by a basic an electrical circuit that utilizes a multi resistor or a solid
state resistor to control different fan speed modes (low, medium low, medium and
high). If the resistor malfunctions the only circuit that remains is the high speed
fan setting.
Basic Heater Circuit
Troubleshooting
- Turn the key to the on position (do not start the engine)
- Inspect system fuse
and replace if needed. Some cars utilize separate circuit fuses in the fuse
box, be sure to inspect all fuses and replace as needed.
- Remove the fan speed resistor component. This resistor is almost always
located in the heater plenum so it can be cooled by the air circulating through
the vents. After the resistor is removed inspect the resistor for obvious burn
marks at any point. If any area shows signs of extreme heat it needs to be replaced.
Reinstall and recheck system.
Troubleshooting
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Blower Fan Works On High Speed Only
Check Manufacturer Specific
Blower
Motor Questions and Answers
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