Daikin Mini Split Error Code J8: How to Fix Oil Thermistor Short

Medium 30-60 minutes Medium Severity Verified June 2026
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Error Code
J8
Brand
Daikin
Product Type
mini_split
Severity
Medium
DIY Difficulty
Medium
Estimated Fix Time
30-60 minutes
Error code J8 on your Daikin mini split indicates an oil thermistor short circuit. This means the sensor that monitors oil temperature has malfunctioned, causing the system to shut down as a safety precaution. DIY fixes include resetting the unit, checking wiring, and replacing the thermistor if needed.
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Tools You'll Need

How to Fix Error Code J8

  1. Power Cycle the Unit

    Always turn off power before inspecting or servicing the unit to avoid electric shock.

  2. Inspect the Oil Thermistor Wiring

    Ensure power is off and capacitors are discharged before handling components.

  3. Test the Oil Thermistor with a Multimeter

  4. Replace a Faulty Oil Thermistor

    Use only replacement parts rated for your specific model to avoid further damage.

  5. Check the Control Board

    Control board testing involves high voltage; only proceed if you are qualified.

Parts You May Need

Oil Thermistor
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Oil Thermistor
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Oil Thermistor
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Oil Thermistor
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When to Call a Professional

If the error persists after replacing the oil thermistor and checking wiring, or if you suspect a control board failure, contact a certified HVAC technician. High-voltage components and refrigerant handling require professional expertise.

Frequently Asked Questions

Can I reset Daikin error code J8 without fixing anything?
Sometimes a simple power cycle (turning off the breaker for 5 minutes) can clear the error if it was caused by a temporary glitch. However, if the thermistor is truly shorted, the error will return.
What causes an oil thermistor short in a Daikin mini split?
Common causes include wiring damage from rodents, moisture corrosion, age-related sensor failure, or power surges that damage the sensor's internal circuitry.
How much does it cost to fix error J8?
DIY cost is about $15-$30 for a replacement thermistor. Professional repair, including diagnosis and labor, typically ranges from $150 to $300.
Is error J8 serious?
Yes, it is medium severity. The system shuts down to prevent compressor damage. Continued operation with a shorted sensor could lead to more expensive repairs.
Can I bypass the oil thermistor?
No, bypassing is not recommended and may void warranty. The thermistor protects the compressor from overheating. Replace it properly.

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