You're right, it's highly unlikely two timers would fail in the same way so quickly. Let's troubleshoot this systematically. Here are some potential causes and how to check them

1. Voltage Stability - The Prime Suspect
Problem

While you measured voltage initially, voltage fluctuations can damage the timer mechanism, even if voltage appears normal.

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Voltage Recorder

The ideal solution is to use a voltage recorder (data logger) for a few days. These are relatively inexpensive to rent. It will show you if there are voltage sags, spikes, or brownouts that are damaging the timer. Even brief fluctuations can be enough to stop the timer.

Multimeter with Min/Max

If you don't have a voltage recorder, use a digital multimeter that can record minimum and maximum voltages over a period of time (ideally a few hours or even a day). While not as precise, it might catch some gross voltage deviations.

Check for Shared Circuits

Are there other devices on the same circuit as the timer that could cause voltage dips when they turn on (e.g., large motors, compressors, welders, HVAC equipment)?

2. Timer Compatibility and Load Problem

Even though the switch works, the type of load (lighting) might be incompatible with the timer's switching mechanism or exceeding its current rating. Though unlikely, LEDs, some fluorescent ballasts, and HID lamps can create inrush current issues.

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Confirm Timer Rating

Double-check the timer's specifications (amps, voltage, type of load it's designed for – resistive, inductive, etc.) against the actual load of the canopy lighting. Is it rated for the inrush current of the lights?

Load Testing

Use an ammeter to measure the actual current draw of the canopy lights when they turn on. Pay special attention to the initial inrush current.

Timer Bypass

Temporarily bypass the timer and connect the lights directly to the power source (using a temporary jumper). Observe if the lights operate normally without any issues. This helps rule out problems with the lights themselves.

3. Neutral Connection Problem

You checked for a neutral, but a weak neutral can still cause problems. The timer's clock mechanism requires a stable, low-impedance neutral return.

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Neutral Voltage to Ground

With the circuit energized and the lights on, measure the voltage between the neutral and ground at the timer location. It should be very close to zero (ideally less than 1-2 volts). Higher voltage indicates a poor neutral connection or excessive neutral current.

Neutral Continuity

De-energize the circuit. Using an ohmmeter, verify the continuity of the neutral wire from the timer back to the panel. Look for high resistance, which would indicate a loose connection or corroded wire.

Check Neutral at the Panel

Make sure the neutral connection at the main panel is tight and clean.

4. Environmental Factors (Even Indoors) Problem

Even though the timer is indoors, there could still be environmental issues affecting it.

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Temperature

Is the location subject to extreme temperature fluctuations (e.g., near a furnace vent, cold drafts)? Extreme temperatures can affect the timer's mechanism.

Vibration

Is there any vibration nearby that could be affecting the timer?

5. Timer Mounting and Mechanical Binding Problem

If the timer is not mounted securely, the internal mechanism could be affected by vibrations or movement. Also, the dial might be binding against the enclosure.

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Mounting Security

Ensure the timer is securely mounted to the wall or enclosure.

Dial Clearance

Verify that the timer dial rotates freely without any obstructions or binding against the enclosure.

6. Power Outage Behavior and Reset Procedures Problem

You mentioned the recent power outage. Even though the owner reset it, there could be a subtle misunderstanding of the reset procedure.

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Verify Resetting Procedure

Double-check the Intermatic timer's manual and confirm the exact procedure for resetting the time after a power outage. Sometimes there's a specific sequence or button to press.

Mark Time on Timer

Before leaving, draw a line on the timer face at the current time with a marker. It may seem silly, but this makes it easy for the customer to see if the dial has moved at all.

7. Adjacent Magnetic Fields Problem

Analog timers rely on a small motor that can be influenced by magnetic fields. If installed close to a large transformer or motor, this could have a negative effect.

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Field Test

Use an EMF reader to test near the timer and see if there are any magnetic fields around it.

Troubleshooting Steps


Start with Voltage Monitoring

The voltage recorder is your best bet.2.

Neutral Check

Conduct a thorough neutral check as described above.3.

Timer Rating and Load Test

Verify the timer's specifications and the actual load of the lights.4.

Environmental Factors

Look for potential environmental issues (temperature, vibration).5.

Reset Procedure: Confirm the correct reset procedure with the owner.Good luck! This sounds frustrating, but by systematically eliminating possibilities, you'll find the root cause. Flag for review