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Error code reference

Denso Air Conditioner Error Code TANK

The drain tank switch has shut off the unit because the drain tank is full (full tank LED flashes).

Denso codesDenso air conditioner codes

The drain tank switch has shut off the unit because the drain tank is full (full tank LED flashes).

First step from the service manual

Drain or remove the drain tank.

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

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What TANK means on a Denso air conditioner

The TANK error code on a Denso air conditioner indicates that the internal drain tank has reached its maximum capacity. Denso portable or spot coolers that lack a direct condensate drain connection collect moisture removed from the air during the cooling process in an onboard drain tank. When this tank fills to capacity, a float-activated drain tank switch triggers, cutting power to the unit and illuminating a flashing full tank LED on the control panel. This is a protective shutdown designed to prevent water overflow and potential damage to flooring, electronics, or the unit itself.

The root cause is always condensate accumulation, but the rate at which the tank fills depends on several factors. High ambient humidity causes the unit to extract significantly more moisture from the air, filling the tank faster than under dry conditions. Extended runtime in a humid environment, inadequate ventilation, or operating the unit in a particularly damp space such as a basement will all accelerate tank fill rate. In some cases, the tank may appear to fill unusually quickly due to a faulty or stuck drain tank switch that is triggering the error prematurely even when the tank is not actually full.

Resolution begins with physically draining or removing the drain tank. Once emptied and reinserted, the switch resets and the unit can resume normal operation. If the error recurs rapidly after draining, or if the tank appears empty when the error triggers, the drain tank switch itself should be inspected for proper function and correct seating.

Source: manufacturer service documentation.

Common causes of TANK

  1. 01

    Full drain tank from normal condensate accumulation

    Wiring / connection

    During normal cooling operation, moisture is continuously extracted from the air and collected in the drain tank. In humid conditions or after extended runtime, the tank simply fills up and triggers the shutoff switch.

  2. 02

    High ambient humidity accelerating fill rate

    Wiring / connection

    Elevated indoor or outdoor humidity causes the unit to extract far more moisture per hour than in dry conditions, causing the tank to reach capacity much faster than expected. This is common in summer months or in naturally damp spaces.

  3. 03

    Infrequent tank draining schedule

    Wiring / connection

    If the drain tank is not emptied on a regular basis suited to the operating environment, it will eventually fill and trigger the error. Establishing a routine draining schedule based on usage and humidity levels prevents recurring shutdowns.

  4. 04

    Faulty or stuck drain tank float switch

    Part replacement

    The drain tank switch uses a float mechanism to detect water level. If the float or switch becomes stuck, corroded, or fails, it can signal a full tank condition even when the tank has little or no water in it. Inspect the switch for physical obstructions or debris.

  5. 05

    Improperly seated or reinstalled drain tank

    Wiring / connection

    If the drain tank was recently removed for emptying and not fully reseated, the switch may not reset correctly, causing the error to persist. Remove the tank completely and firmly reinsert it to ensure proper contact with the switch.

See the test procedure for each cause

Frequently asked questions about TANK

What does TANK mean on a Denso air conditioner?
The TANK error on a Denso air conditioner means the internal condensate drain tank is full. The unit collects moisture removed from the air during cooling in this onboard tank, and when it reaches capacity, a float-activated switch shuts the unit off to prevent overflow. The full tank LED will flash on the control panel to confirm this condition.
How do I fix the TANK error on my Denso air conditioner?
Remove or drain the condensate tank, empty it completely, and then firmly reinsert it into the unit. Once the tank is properly seated and no longer full, the drain tank switch will reset and the unit should resume normal operation. If the error returns quickly after draining, inspect the float switch for debris or a stuck position.
Is it safe to keep running my Denso air conditioner when the TANK error appears?
No. The unit automatically shuts itself off when the TANK error triggers, and you should not attempt to bypass this shutoff. Running the unit with a full drain tank risks water overflow, which can damage flooring, nearby equipment, or the internal components of the air conditioner itself.
Will resetting my Denso air conditioner clear the TANK error?
A simple power reset will not clear the TANK error because the drain tank float switch remains activated as long as the tank is full. The tank must be physically emptied and correctly reseated before the switch resets and the error clears. Only after draining the tank will the unit be able to restart.
How much does it cost to repair a Denso air conditioner showing the TANK error?
In most cases there is no repair cost at all, since draining the tank is a free maintenance task the owner can perform. If the drain tank switch has failed and requires replacement, parts and labor costs typically range from $50 to $150 depending on part availability and service rates in your area. Recurring errors in low-humidity conditions are the main indicator that a switch replacement may be needed.

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