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Error code reference

Denso Air Conditioner Error Code OL

Compressor overload relay activated due to high temperature build-up in compressor.

Denso codesDenso air conditioner codes

Compressor overload relay activated due to high temperature build-up in compressor.

First step from the service manual

Repair the leaking section and recharge the correct amount of refrigerant, then RESET the controller.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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What OL means on a Denso air conditioner

The OL error code on a Denso air conditioner indicates that the compressor overload relay has been activated due to excessive heat buildup within the compressor. The overload relay is a protective device that monitors compressor operating temperature and cuts power to the compressor when temperatures exceed safe thresholds. This protection mechanism exists to prevent permanent compressor damage, winding failure, or even fire risk from a severely overheated motor.

The most direct cause of this overload condition is typically a refrigerant leak within the system. When refrigerant charge drops below the specified level, the compressor is forced to work harder to maintain system pressure, generating significantly more heat than it would under normal operating conditions. Insufficient refrigerant also reduces the cooling effect that the refrigerant itself provides to the compressor motor, compounding the heat problem. Other contributing factors can include restricted airflow across the condenser coil, a failing condenser fan motor, or an ambient temperature environment that pushes the system beyond its rated operating range.

Diagnosing and resolving the OL code requires locating and repairing the refrigerant leak before recharging the system to the correct specified refrigerant quantity. Simply recharging without addressing the leak will result in the same error returning as refrigerant escapes again. After the leak is repaired and the proper charge is restored, the controller must be reset to clear the fault. Technicians should also inspect the condenser section for blocked airflow, dirty coils, or a malfunctioning fan motor that could contribute to ongoing overload conditions.

Source: manufacturer service documentation.

Common causes of OL

  1. 01

    Refrigerant leak causing low charge

    Part replacement

    A leak in the refrigerant circuit reduces system charge, forcing the compressor to overwork and overheat. Look for oily residue around refrigerant line connections, fittings, or the coil as an indicator of a leak point.

  2. 02

    Blocked or restricted condenser airflow

    Wiring / connection

    Debris, dirt, or obstructions around the condenser unit prevent adequate heat dissipation, causing compressor temperatures to climb. Inspect the condenser coil for heavy dirt buildup and ensure at least the minimum required clearance around the outdoor unit.

  3. 03

    Condenser fan motor failure

    Part replacement

    If the condenser fan motor is running slowly or has stopped, heat cannot be expelled from the refrigerant circuit efficiently, leading to compressor overload. Check that the fan spins freely, runs at the correct speed, and draws appropriate current.

  4. 04

    Compressor overload relay fault

    Part replacement

    The overload relay itself may be faulty and tripping prematurely even when compressor temperature is within acceptable range. This is less common but should be evaluated after refrigerant and airflow issues have been ruled out.

  5. 05

    Excessively high ambient temperature

    Wiring / connection

    Operating the unit in ambient conditions beyond its rated temperature range can push the compressor into overload even with a correct refrigerant charge and clean components. Verify the installation environment against the unit's specified operating limits.

See the test procedure for each cause

Frequently asked questions about OL

What does OL mean on a Denso air conditioner?
The OL code on a Denso air conditioner means the compressor overload relay has activated due to high temperature buildup inside the compressor. This is a protective shutdown designed to prevent compressor damage. The most common trigger is a refrigerant leak that causes the system to run low on charge, forcing the compressor to overheat. The system will not resume normal operation until the underlying cause is corrected and the controller is reset.
How do I fix the OL error code on my Denso air conditioner?
Fixing the OL code requires identifying and repairing the source of any refrigerant leak, then recharging the system with the correct amount of refrigerant. Once the repair is complete, the controller must be manually reset to clear the fault. You should also check the condenser coil for dirt buildup and confirm the condenser fan is operating correctly, as restricted airflow can contribute to compressor overheating.
Is it safe to keep running my Denso air conditioner when the OL code is active?
No, you should not attempt to bypass or ignore the OL error. The overload relay has shut down the compressor specifically to protect it from heat damage. Continuing to force operation without resolving the root cause, typically a refrigerant leak or airflow restriction, risks permanent compressor failure, which is a significantly more expensive repair than addressing the original problem.
Will resetting the controller clear the OL code on a Denso air conditioner?
A controller reset is required as part of the repair process, but it should only be performed after the underlying cause has been corrected. If the refrigerant leak is repaired and the system is properly recharged before the reset, the code should clear and normal operation should resume. Resetting without fixing the root cause will result in the OL code returning once the compressor overheats again.
How much does it cost to repair an OL error code on a Denso air conditioner?
Repair costs vary depending on the cause and severity of the problem. A straightforward refrigerant leak repair combined with recharging typically falls in the range of $150 to $500 or more, depending on the leak location, refrigerant type, and labor rates in your area. If the compressor overload relay itself needs replacement, parts and labor add additional cost. A full compressor replacement, needed only in severe cases, can range from $800 to several thousand dollars.

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