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Error code reference

Friedrich Air Conditioner Error Code E6

Indoor probe short

Friedrich codesFriedrich air conditioner codes

Indoor probe short: control assumes ambient temperature is 90°F and unit will operate.

First step from the service manual

Replace probe.

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

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What E6 means on a Friedrich air conditioner

The E6 error code on a Friedrich air conditioner indicates a short circuit condition in the indoor ambient temperature probe. This probe is a thermistor, a resistive sensor whose resistance changes predictably with temperature. When the control board detects a resistance value that falls below the expected range, it interprets this as a short circuit. A shorted thermistor typically reads near-zero resistance, which would correspond to an extremely high temperature in a normal operating curve. Rather than shutting down entirely, the Friedrich control system defaults to a fixed assumed ambient temperature of 90°F, allowing the unit to continue running under this preset value.

Because the unit is operating on an assumed temperature rather than a real-time reading, it cannot accurately regulate cooling cycles based on actual room conditions. This means the compressor and fan may cycle at incorrect intervals, potentially leading to overcooling, undercooling, or inefficient energy use. The root cause is almost always a failure within the probe itself or the wiring harness connecting it to the control board.

The primary diagnostic action is replacement of the indoor probe. Before replacing, inspect the probe wiring for any pinched, chafed, or melted insulation that could be causing the wiring to short against the chassis or another conductor. If the wiring is intact, the thermistor element itself has failed internally and the probe assembly must be replaced to restore accurate temperature sensing and normal control board operation.

Source: manufacturer service documentation.

Common causes of E6

  1. 01

    Failed indoor thermistor probe

    Part replacement

    The thermistor element inside the probe has internally short-circuited, dropping its resistance to near zero. This is the most common cause and requires replacing the probe assembly.

  2. 02

    Pinched or damaged probe wiring

    Wiring / connection

    The wiring harness connecting the probe to the control board can become pinched during reassembly or chafed against a metal edge, creating a short to ground. Inspect the full wire run for visible insulation damage.

  3. 03

    Corroded or shorted probe connector

    Wiring / connection

    Moisture or debris at the connector between the probe lead and the control board can bridge the terminals and simulate a short. Check the connector pins for corrosion, moisture, or bent contacts.

  4. 04

    Control board fault

    Part replacement

    In rare cases, the input circuit on the control board itself may have failed, causing it to incorrectly report a short even when the probe is good. This is typically ruled out only after confirming the probe and wiring test correctly.

See the test procedure for each cause

Frequently asked questions about E6

What does E6 mean on a Friedrich air conditioner?
E6 indicates that the indoor ambient temperature probe has been detected as shorted by the control board. Because a shorted thermistor reads near-zero resistance, the control cannot determine the actual room temperature. The Friedrich control system responds by assuming a fixed ambient temperature of 90°F and allowing the unit to continue operating under that preset value.
Can I fix the E6 error myself, or do I need a technician?
A knowledgeable DIYer can visually inspect the probe wiring and connector for obvious damage or corrosion without specialized tools. However, actually testing the thermistor resistance and replacing the probe requires disassembling the unit and working near electrical components, so comfort with appliance repair is important. If you are not confident in those steps, a qualified technician is the safer choice.
Is it safe to keep running my Friedrich air conditioner while E6 is displayed?
The unit will continue to operate using the assumed 90°F ambient reading, so it is not in immediate danger of damaging itself from this fault alone. However, because the unit cannot read actual room temperature, it may not cool efficiently or cycle correctly, which could lead to comfort issues and higher energy use. Running it long-term without resolving the probe fault is not recommended.
Will resetting the air conditioner clear the E6 code?
A power reset will temporarily clear the displayed code, but the E6 fault will return as soon as the control board re-checks the probe and detects the short again. The code will persist until the underlying problem, either the failed probe or damaged wiring, is physically corrected.
How much does it cost to repair an E6 error on a Friedrich air conditioner?
If only the indoor temperature probe needs replacement, parts typically range from a few dollars to around $30 to $50 depending on the specific model, making it one of the lower-cost repairs. If a technician is needed for diagnosis and replacement, total costs including labor generally fall in the $75 to $200 range. A control board replacement, needed only in rare cases, would add significantly to that estimate.

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