Solenoid Valve Coil Burnout / Open Circuit
A field reference for solenoid valve faults — what causes it, how to confirm it on the unit, how to repair it, and what fails next if you leave it. Written for working HVAC & refrigeration technicians.
How to confirm it on site
- Coil DC resistance — outside normal range (typically 20–80Ω) or ∞ (open)
- No plunger click (audible actuation) when energized
- Coil surface discoloration (burnt) or insulation cracking
- Current draw — 0A when energized (open) or 200%+ rated (short)
Root causes
- Over-voltage (e.g. 220V applied to 24V coil — wiring error)
- Frequency mismatch (50Hz coil on 60Hz supply)
- Heat accumulation — 100% duty operation on non-rated coil
- Insulation aging — winding insulation failure after 10+ years
- Moisture ingress — IP rating insufficient or seal damage
If you leave it unrepaired
- Valve fails to actuate — open/close commands ignored → circuit isolation fails
- Liquid line SV burnout: pump-down impossible → liquid migration to compressor when off
- Next startup: liquid slugging → compressor valve/piston damage risk
- Hot-gas SV burnout: defrost fails → evaporator ice accumulates → refrigeration capacity drops
- Eventually system shutdown or compressor burn-out
How to fix it
- Power off → replace coil only (valve body preserved → no pump-down needed)
- Verify replacement coil spec — voltage/frequency/lead wiring matched
- Prevent recurrence: re-check wiring + measure insulation resistance (≥1MΩ)
- If seat damage suspected: replace full valve body (requires vacuum + recovery)
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What causes solenoid valve coil burnout / open circuit?
Over-voltage (e.g. 220V applied to 24V coil — wiring error) Frequency mismatch (50Hz coil on 60Hz supply) Heat accumulation — 100% duty operation on non-rated coil Insulation aging — winding insulation failure after 10+ years Moisture ingress — IP rating insufficient or seal damage
How do I diagnose solenoid valve coil burnout / open circuit on site?
Coil DC resistance — outside normal range (typically 20–80Ω) or ∞ (open) No plunger click (audible actuation) when energized Coil surface discoloration (burnt) or insulation cracking Current draw — 0A when energized (open) or 200%+ rated (short)
How do I fix solenoid valve coil burnout / open circuit?
Power off → replace coil only (valve body preserved → no pump-down needed) Verify replacement coil spec — voltage/frequency/lead wiring matched Prevent recurrence: re-check wiring + measure insulation resistance (≥1MΩ) If seat damage suspected: replace full valve body (requires vacuum + recovery)
What happens if solenoid valve coil burnout / open circuit is left unrepaired?
Valve fails to actuate — open/close commands ignored → circuit isolation fails Liquid line SV burnout: pump-down impossible → liquid migration to compressor when off Next startup: liquid slugging → compressor valve/piston damage risk Hot-gas SV burnout: defrost fails → evaporator ice accumulates → refrigeration capacity drops Eventually system shutdown or compressor burn-out