Heater displays E13; ignition sequence may not start

Safety: Turn off power at the breaker before opening the electrical junction box or control compartment.

• Verify supply voltage: With a multimeter and power restored, measure voltage at the heater's line terminals. Compare to the SunHeater rating (e.g., 120V or 240V). If voltage is more than 10% low, consult an electrician.
• Inspect wiring connections: Turn power off again. Tighten all lugs and wire nuts in the heater's junction box and at the main control board. Look for signs of overheating or discoloration.
• Check transformer output: Locate the Control Transformer and measure its low-voltage output (typically 24VAC) with power on. If output is low or intermittent, replace the transformer.
• Reduce shared loads: Ensure the heater is on a dedicated circuit sized per the installation manual. Do not share the circuit with large pumps or other heavy loads that can cause voltage drops.
• Test after corrections: Once wiring and voltage are corrected, clear the error by cycling power and attempt to start the heater.