A9905420018 Pressure Switch Mercedes Benz Truck Parts 0045429018

1.Quick Notice

A9905420018 pressure switch for Mercedes-Benz trucks and commercial vehicles. OE-number direct replacement part. Functions as air conditioning pressure switch or general pressure monitoring device depending on vehicle application. Thread seal ring not included. Verify connector type, thread size, and pressure range before ordering. Professional installation recommended.

2.Description

The A9905420018 pressure switch is an OE-number electrical component manufactured for Mercedes-Benz vehicle applications. This part number is recognized across multiple Mercedes-Benz commercial vehicle platforms including Actros, Axor, Atego, and Zetros truck series 2. The switch monitors pressure levels within a fluid or gas system and provides an electrical signal at preset pressure thresholds.

The most documented application for this pressure switch family is in air conditioning refrigerant circuits. The switch monitors high-side refrigerant pressure in R134a air conditioning systems and opens or closes the compressor clutch circuit when pressure exceeds or falls below calibrated limits 1. This protects the AC compressor from operating under conditions that could cause internal damage.

The switch body is manufactured from injection-molded thermoplastic rated for under-hood and HVAC module environments. The material formulation resists ozone exposure, refrigerant oils, and underhood temperature cycling from -30°C to +100°C. The housing incorporates a locking tab pattern for the electrical connector to prevent accidental disconnection during vehicle operation.

Internally, the switch contains a diaphragm-actuated snap-action mechanism. System pressure acts against one side of the diaphragm. When pressure reaches the calibrated trip point, the diaphragm overcomes spring tension and flips the electrical contact state. This snap-action design provides crisp switching with minimal contact hesitation or arcing.

The switching function can be normally open or normally closed depending on the specific vehicle application. In air conditioning duty, the switch typically opens the compressor clutch circuit when refrigerant pressure becomes too high or too low. Some applications use the switch to activate condenser cooling fans or send pressure data to the engine control module.

The electrical interface uses a multi-pin sealed connector. Pin count varies by specific vehicle fitment. Common configurations include two-pin for simple on-off switching and three-pin for pressure monitoring with multiple switching thresholds 1. The connector incorporates a rubber gasket seal at the mating face to exclude moisture and contaminants.

The threaded mounting boss incorporates an O-ring groove or a flat sealing face requiring a separate seal ring 1. No seal is included with the switch. The thread size commonly associated with this switch family is 3/8-24 UNF 1.

This replacement switch suits vehicles where the air conditioning compressor fails to engage, remains engaged regardless of system state, or cycles excessively. Also replace the switch when visible refrigerant oil residue appears around the switch threads or electrical connector.

3.Parameter Table

4.Custom Content

Application notes for A9905420018 pressure switch. This part number is listed in Mercedes-Benz electronic parts catalogs under multiple supersession paths. The switch serves different functions across different chassis and model years. Always confirm the original switch connector shape and pin count before ordering.

Air conditioning system installation. Recover refrigerant from the AC system before removing the old switch. Use a proper recovery machine. Do not vent refrigerant to atmosphere. Clean the mounting port threads. Install a new seal ring on the switch threads. Hand-thread the switch into the port. Torque to 8 to 12 Nm. Overtightening cracks the switch housing or damages the port threads. Evacuate and recharge the system after installation. Leak test the switch area with electronic detector or soap solution.

Pressure monitoring system installation. For trucks using this switch as a general pressure monitor, drain the system or isolate the switch port before removal. Clean debris from the port threads. Apply thread sealant compatible with the system fluid. Thread sealant prevents leaks without overtorquing. Torque to specification for the specific port type.

Electrical testing. With the system at rest and no pressure applied, use a multimeter to check continuity across the switch terminals. Known good switches show either continuity or no continuity depending on normal state design. Apply pressure while monitoring continuity. The switch should change state when system pressure crosses the calibrated threshold. No state change indicates a failed switch.

Cross-reference notes. The A9905420018 number appears in aftermarket catalogs cross-referenced to additional OE numbers including 0045429018, 2205420118, and 2110000283 1. These numbers represent superseded versions or application-specific variants. All share the same basic thread and connector specifications.

5.FAQ (Q&A Format)

Q1: Which Mercedes-Benz trucks use the A9905420018 pressure switch?
A1: This pressure switch fits Mercedes-Benz Actros MP2/MP3, Axor, Atego (both first and second generation), and Zetros truck models 2. Verify application by checking your original part number.

Q2: Is this switch used only for air conditioning systems?
A2: The primary documented application is AC refrigerant pressure monitoring. However, cross-reference listings suggest potential use in general pressure monitoring systems on certain chassis 12.

Q3: What refrigerant is compatible with this switch?
A3: This switch is specified for R134a refrigerant systems 1. It is not compatible with R1234yf systems unless confirmed by OE documentation.

Q4: Does the switch come with a seal ring or gasket?
A4: No. The switch requires a separate seal ring. The manufacturer specification indicates "with seal ring" as an additional item, not included 1.

Q5: How many electrical terminals does this switch have?
A5: The A9905420018 typically has a 3-pin connector 1. However, some applications use a 2-pin configuration. Count the terminals on your original switch before ordering.

Q6: What is the thread size for mounting this switch?
A6: The thread size is 3/8-24 UNF male 1. This is a standard United National Fine thread. Do not force the switch into metric ports.

Q7: What causes repeated pressure switch failure in Mercedes-Benz trucks?
A7: Common causes include contaminated refrigerant, compressor debris circulating through the system, overpressure events due to failed condenser fan, or electrical shorts in the compressor clutch circuit.

Q8: How can I test if my pressure switch has failed?
A8: Test continuity across switch terminals with AC system static. Bypass the switch temporarily. If compressor engages with switch bypassed but not normally, the switch has failed open. If compressor runs continuously regardless of pressure, the switch has failed closed.

Q9: Is this switch interchangeable with A0045429018?
A9: Yes. A0045429018 and A9905420018 are listed as cross-reference numbers for the same component family 1. Always verify connector and thread match your original part.

Q10: What operating pressure range does this switch handle?
A10: For pressure monitoring applications in truck systems, related part numbers in this family specify maximum operating pressure up to 20 bar 2. AC switch pressure thresholds vary by calibration. Consult your vehicle service manual for exact trip pressure values.