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Error code reference

Dacor Oven Error Code L43

Lower relay board no zero crossing (ZC) detected on relay board.

Dacor codesDacor oven codes

Lower relay board no zero crossing (ZC) detected on relay board.

First step from the service manual

Verify connections are proper on S19. Secure connections at S19, then replace relay board.

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

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What L43 means on a Dacor oven

The L43 error code on a Dacor oven indicates that the lower relay board is not detecting a zero crossing (ZC) signal. Zero crossing refers to the point in an AC power cycle where the voltage waveform transitions through zero volts, crossing from positive to negative or vice versa. The relay board uses this zero crossing signal to synchronize the switching of relays precisely at that moment, which minimizes electrical arcing and component wear. Without a valid ZC signal, the relay board cannot operate safely or accurately, and the control system flags the fault.

The zero crossing signal is typically generated by a dedicated circuit on the relay board itself and is monitored by the main control board. When this communication breaks down, it can indicate a problem at the connector point S19, which is the interface between the wiring harness and the lower relay board. Loose, corroded, or improperly seated connections at S19 can interrupt the signal path and produce this fault without any actual failure of the relay board itself.

If securing and verifying the connections at S19 does not resolve the fault, the lower relay board is likely defective and will need to be replaced. A failed zero crossing detection circuit on the board, damaged traces, or a failed ZC sensing component on the board can all prevent the signal from being generated or transmitted correctly. This is a control and power management fault that should be addressed before continuing to use the oven, as improper relay switching can cause premature component failure.

Source: manufacturer service documentation.

Common causes of L43

  1. 01

    Loose or unseated connector at S19

    Wiring / connection

    The connector at S19 links the wiring harness to the lower relay board. If this connector is loose, partially unplugged, or improperly seated, the zero crossing signal cannot pass through, triggering the L43 fault.

  2. 02

    Corroded or damaged connector pins at S19

    Wiring / connection

    Corrosion, bent pins, or heat damage at the S19 connector can interrupt the signal even if the connector appears to be seated. Inspect each pin for discoloration, oxidation, or physical deformation.

  3. 03

    Failed lower relay board

    Part replacement

    If the zero crossing detection circuit on the relay board itself has failed due to a damaged component or broken trace, the board will not generate or transmit the ZC signal regardless of connection quality. Replacement of the relay board is required.

  4. 04

    Damaged wiring harness between S19 and the relay board

    Part replacement

    A pinched, burned, or broken wire in the harness leading to S19 can sever the signal path. Inspect the harness for visible damage, especially near areas exposed to heat from oven operation.

See the test procedure for each cause

Frequently asked questions about L43

What does L43 mean on a Dacor oven?
L43 means the lower relay board is not detecting a zero crossing signal, which is a timing reference the board needs to switch heating relays correctly within the AC power cycle. This fault is flagged when the control system loses communication with the zero crossing circuit on the lower relay board. It typically points to a connection issue at connector S19 or a failed relay board.
Can I fix the L43 error myself?
The first diagnostic step is to check and secure the connections at connector S19 on the lower relay board, which does not require replacing any parts. If the connections are intact and secure but the fault persists, the lower relay board will need to be replaced, which is a more involved repair. Technicians comfortable with appliance disassembly and electrical connectors can often perform this repair, but working near high-voltage components carries risk and caution is advised.
Is it safe to use my Dacor oven with the L43 error code?
It is not recommended to continue using the oven while the L43 fault is active. The zero crossing signal is used to synchronize relay switching, and operating without it can cause improper relay timing, which may lead to premature relay failure or other component damage. The oven should be repaired before resuming normal use.
Will resetting the oven clear the L43 error code?
A power reset may temporarily clear the fault display, but if the underlying issue at connector S19 or on the relay board is not corrected, the L43 code will return once the oven attempts to operate. A reset alone is not a fix and should not be used as a substitute for diagnosing the root cause.
How much does it cost to repair a Dacor oven showing L43?
If only the S19 connector needs to be reseated, there may be no parts cost involved, though a service call fee typically applies and can range from $75 to $150 depending on your area. If the lower relay board needs to be replaced, the part cost can range from $150 to $350 or more depending on the specific model, with total repair costs including labor generally falling between $250 and $500.

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