3-Pin Coolant Temperature & Cooling Fan Connector – VW Audi Skoda OEM 1J0973203
Direct-fit replacement for VW Group OEM part number 1J0973203 (also written as 1J0 973 203), a 3-pin connector used for coolant temperature sensor (CTS), radiator cooling fan switch, and thermostat harness connections on VW, Audi, and Skoda platforms. This connector is one of the most commonly replaced harness connectors on VW Group vehicles due to heat cycling and coolant exposure causing terminal corrosion.
Key Specifications
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OEM Part Number: 1J0973203 / 1J0 973 203 (VW Group)
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Pin Count: 3
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Gender: Female (with wire)
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Wire Gauge: 20 AWG (0.5 mm²)
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Wire Length: 5.5 inches (140 mm)
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Housing Material: PA66 glass-filled nylon (heat-resistant)
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Terminal Material: Copper alloy, tin-plated
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Current Rating: Up to 5A per pin
Coolant Temperature Sensor Pin Assignment (3-Pin)
| Pin |
Circuit |
| 1 |
Signal output to ECU (coolant temp) |
| 2 |
Ground / signal return |
| 3 |
Cooling fan switch signal (dual-function sensor) |
Compatible VW / Audi / Skoda Applications
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VW Golf IV / Jetta IV / Bora (1J platform): Coolant temperature sensor and cooling fan switch connector
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VW Passat B5: Radiator coolant temperature sensor harness connector
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Audi A3 (8L) / A4 (B5/B6): CTS and thermostat harness connector
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Skoda Octavia (1U): Cooling fan switch and CTS connector
1J0973203 – Why This Connector Fails
The 1J0973203 is located in the engine bay near the coolant system, where it is exposed to heat cycling, coolant spray, and vibration. The most common failure modes are:
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Terminal corrosion: Coolant residue causes green oxidation on the copper terminals, increasing contact resistance and causing intermittent CTS signal faults
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Housing brittleness: Repeated heat cycling causes the PA66 housing to become brittle and crack, breaking the locking tab and causing the connector to fall off the sensor
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Wire insulation hardening: Heat causes the wire insulation to harden and crack near the connector entry point, causing open-circuit faults
Diagnosis
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P0115–P0118 (ECT Circuit): Check connector before replacing sensor – a corroded 1J0973203 connector is the most common cause of these codes on VW/Audi
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Cooling fan not switching on: Inspect Pin 3 (fan switch signal) – an open circuit at the connector prevents the fan from activating at temperature threshold
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VCDS live data: Monitor G62 (coolant temperature sensor) in real time – an erratic or stuck reading at -40°C or 130°C indicates a connector fault, not a sensor fault
FAQ
Q: Is 1J0973203 the same as 1J0 973 203?
A: Yes – these are the same VW Group part number written in two formats (with and without spaces). Both refer to the identical connector.
Q: Can a bad 1J0973203 connector cause overheating?
A: Yes – if the cooling fan switch signal (Pin 3) is interrupted by a corroded connector, the cooling fan will not activate at the correct temperature threshold, potentially causing engine overheating.
Package Contents
1 × 3-Pin Female Connector (1J0973203) with 20 AWG wire and terminal insert
