Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSAUDI199590 QUATTRO SPORT V6-2.8L (AAH)REPAIR AND DIAGNOSISHEATING AND AIR CONDITIONINGREFRIGERANT PRESSURE SENSOR / SWITCHLOW PRESSURE SENSOR / SWITCHSERVICE AND REPAIR
1995 Audi 90 Quattro Sport V6-2.8L (AAH)
Low Pressure Sensor / Switch: Service and Repair
1995 Audi 90 Quattro Sport V6-2.8L (AAH)SECTION Service and Repair
Location: In passenger compartment on the passenger side between heater housing and bulkhead.
Function:
- Switches A/C clutch -N25- off if system suction pressure is too low (low refrigerant charge). This switch protects the compressor if the refrigerant system is empty.
- Switch opens (compressor off): 1.45 - 1.6 bar (21 - 23 psi)
- Switch closes (compressor on): 2.9 - 3.4 bar (42 - 49 psi)
Removing And Installing:
- Remove passenger side lower instrument panel cover.
- Remove Engine Control Module (ECM) -A- in direction of arrow. See Powertrain Management.
- Disconnect electrical connector from low pressure switch -F73-.
- Using 17 mm open end wrench approx. 80 mm (3 in.) long, remove low pressure switch.
- Refrigerant system remains closed (Schrader valve under switch).
NOTE: Image shows low pressure switch -F73- with the heater housing removed.
- Install new 0-ring -A- (8.9 mm x 1.8 mm), lubricate with refrigerant (PAG) oil and make sure it is properly seated in groove.
- Install switch.
- Tightening torque: 5 Nm (44 in. lb)
- Reinstall Engine Control Module (ECM) and passenger side lower instrument panel cover
Function:
- Switches A/C clutch -N25- off if system suction pressure is too low (low refrigerant charge). This switch protects the compressor if the refrigerant system is empty.
- Switch opens (compressor off): 1.45 - 1.6 bar (21 - 23 psi)
- Switch closes (compressor on): 2.9 - 3.4 bar (42 - 49 psi)
Removing And Installing:
- Remove passenger side lower instrument panel cover.
- Remove Engine Control Module (ECM) -A- in direction of arrow. See Powertrain Management.
- Disconnect electrical connector from low pressure switch -F73-.
- Using 17 mm open end wrench approx. 80 mm (3 in.) long, remove low pressure switch.
- Refrigerant system remains closed (Schrader valve under switch).
NOTE: Image shows low pressure switch -F73- with the heater housing removed.
- Install new 0-ring -A- (8.9 mm x 1.8 mm), lubricate with refrigerant (PAG) oil and make sure it is properly seated in groove.
- Install switch.
- Tightening torque: 5 Nm (44 in. lb)
- Reinstall Engine Control Module (ECM) and passenger side lower instrument panel cover
RENDER: 1.0x
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.