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LENNOX SL18XC1 Starts Then Shuts Off

CONF DIAGNOSIS ACTION
91%
CONF
Dual Run Capacitor
The capacitor provides the necessary phase-shifted current to the compressor's start winding. When the capacitance drops below the required microfarad (µF) rating, the compressor draws excessive amperage during the transition from startup to run mode. This causes the internal bimetallic thermal protector to trip, shutting the unit down to prevent winding melt-down.
VIEW ON AMAZON #CommissionsEarned
5%
CONF
High Pressure Switch
This is a safety device designed to open the 24V control circuit if internal refrigerant pressures exceed safe operating limits (typically 550-650 PSI for R-410A). If the outdoor fan motor fails to move sufficient air across the condenser coils, the refrigerant cannot reject heat, causing a rapid pressure spike that triggers this switch to instantly terminate the cycle.
SKU: 100448-03
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4%
CONF
AC Contactor
The contactor is an electromechanical relay that closes the high-voltage path to the compressor. Over time, the silver-cadmium contacts develop 'pitting' or carbon arc tracks; this increases electrical resistance and can cause the contacts to 'chatter' or drop out under the heavy inductive load of the compressor, resulting in an immediate shutdown.
SKU: 10F73
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DIY Repair Guide

Watch exactly how to replace the Dual Run Capacitor.

// NOTICE: This report is generated by an Agentic AI Engineer utilizing probabilistic modeling.

PartSniper is an automated parts recommender service. AI-generated results may not be correct. This data is not a substitute for professional engineering advice or manual inspection. Always verify part compatibility and disconnect power before any repair. PartSniper is not liable for inaccuracies, injury, or damage.

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