❄️ Dual Pressure Switch – Function in Car A/C System
🔧 1. Purpose
The dual pressure switch is a safety and control device used in many automotive air conditioning systems. It monitors both high and low refrigerant pressures and protects the A/C compressor from damage.
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⚙️ 2. Main Function
It performs two opposite but equally important tasks:
Condition Pressure Side Switch Action Purpose / Result
Low Pressure (Too little refrigerant or leak) Low side Opens circuit (turns OFF compressor clutch) Prevents compressor from running dry — avoids lack of lubrication and internal damage High Pressure (Overcharge or airflow restriction) High side Opens circuit (turns OFF compressor clutch) Prevents system from over-pressurizing, avoiding hose burst or compressor overload
When pressure returns to normal range, the switch closes again, allowing the compressor clutch to engage.
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🔋 3. Operating Pressure Range (Typical Values)
Function Approx. Pressure (psi)
Low pressure cut-off 25–30 psi Low pressure cut-in 40–45 psi High pressure cut-off 400–450 psi High pressure cut-in 250–300 psi
(Values vary depending on vehicle and refrigerant type — R134a, R1234yf, etc.)
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📍 4. Location
The dual pressure switch is normally installed on the high-pressure line, usually:
On the receiver-drier, accumulator, or discharge line between compressor and condenser.
It will have 2 or 3 electrical terminals (older systems use 2; newer ones may have 3 or 4 for signal feedback).
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🧠 5. How It Works Electrically
The switch is wired in series with the A/C compressor clutch relay.
When the pressure is within safe limits, the switch closes, completing the circuit → Compressor runs.
If pressure is too low or too high, it opens, breaking the circuit → Compressor stops immediately.
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⚠️ 6. Importance in System Protection
Prevents compressor damage due to refrigerant loss
Prevents system overpressure and bursting
Ensures efficient cooling by maintaining proper refrigerant cycle conditions
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🧰 7. Quick Diagnostic Tip
To test:
1. Locate the dual pressure switch (usually on the high side line).
2. Check continuity with a multimeter:
Normal pressure = continuity present (switch closed).
Low/high pressure = open circuit (no continuity).
3. Never bypass the switch permanently — only temporarily for test purposes and with gauges connected.
Master Mechanic Abhishek
❄️ Dual Pressure Switch – Function in Car A/C System
🔧 1. Purpose
The dual pressure switch is a safety and control device used in many automotive air conditioning systems.
It monitors both high and low refrigerant pressures and protects the A/C compressor from damage.
---
⚙️ 2. Main Function
It performs two opposite but equally important tasks:
Condition Pressure Side Switch Action Purpose / Result
Low Pressure (Too little refrigerant or leak) Low side Opens circuit (turns OFF compressor clutch) Prevents compressor from running dry — avoids lack of lubrication and internal damage
High Pressure (Overcharge or airflow restriction) High side Opens circuit (turns OFF compressor clutch) Prevents system from over-pressurizing, avoiding hose burst or compressor overload
When pressure returns to normal range, the switch closes again, allowing the compressor clutch to engage.
---
🔋 3. Operating Pressure Range (Typical Values)
Function Approx. Pressure (psi)
Low pressure cut-off 25–30 psi
Low pressure cut-in 40–45 psi
High pressure cut-off 400–450 psi
High pressure cut-in 250–300 psi
(Values vary depending on vehicle and refrigerant type — R134a, R1234yf, etc.)
---
📍 4. Location
The dual pressure switch is normally installed on the high-pressure line, usually:
On the receiver-drier, accumulator, or discharge line between compressor and condenser.
It will have 2 or 3 electrical terminals (older systems use 2; newer ones may have 3 or 4 for signal feedback).
---
🧠 5. How It Works Electrically
The switch is wired in series with the A/C compressor clutch relay.
When the pressure is within safe limits, the switch closes, completing the circuit → Compressor runs.
If pressure is too low or too high, it opens, breaking the circuit → Compressor stops immediately.
---
⚠️ 6. Importance in System Protection
Prevents compressor damage due to refrigerant loss
Prevents system overpressure and bursting
Ensures efficient cooling by maintaining proper refrigerant cycle conditions
---
🧰 7. Quick Diagnostic Tip
To test:
1. Locate the dual pressure switch (usually on the high side line).
2. Check continuity with a multimeter:
Normal pressure = continuity present (switch closed).
Low/high pressure = open circuit (no continuity).
3. Never bypass the switch permanently — only temporarily for test purposes and with gauges connected.
#acdualpressureswitch #dualpressureswitch
2 weeks ago (edited) | [YT] | 4