Formiden Engine Coolant Temperature Sensor G1852 with Pigtail Harness — Brass, fits Classic GM 1950s–1970s

Formiden G1852 (12334869) is a complete replacement engine coolant temperature sensor kit with a brass sender and pigtail harness made to restore accurate temperature readings on classic GM cars and trucks.

Designed for restored and well-loved vintage General Motors vehicles, this kit replaces worn or brittle factory sensors and connectors. It provides the sensor element and a pre-assembled wiring pigtail to avoid unreliable splices and aged plastic connectors. The kit fits many Chevy, Buick, Pontiac, Oldsmobile, Cadillac and GMC applications from the mid-1950s through the late 1970s when used with matching thread and part-number cross-reference.

How does this sensor kit fit my classic GM engine?

The sensor uses a 1/2"-14 NPT (0.840" diameter) thread common to many period intake manifolds and cylinder heads. Use the OEM cross-reference numbers supplied to confirm compatibility with your vehicle and engine. If your original part number matches any listed references, this kit is a direct aftermarket replacement.

• Thread spec: 1/2"-14 NPT (standard NPT taper thread)
• Direct replacement numbers: G1852, 12334869, 12334870, 1512678, J914847, and others
• Typical mounting locations: intake manifold or cylinder head temperature port
• Designed for classic GM models from ~1950s–1970s

What exactly comes in the package and why replace both parts?

The kit ships with one brass temperature sensor and one pre-wired pigtail harness with a connector. Replacing the harness and sensor together prevents electrical issues caused by brittle original connectors and corroded terminals. A new harness saves time and reduces the chance of intermittent gauge readings after installation.

• 1 x brass engine coolant temperature sensor
• 1 x pigtail wiring harness with molded connector
• No splicing required; ready to plug into factory wiring
• Installation-ready for standard gauge or warning light systems

How do I install the sensor safely on my classic vehicle?

Install after the engine has cooled and, if necessary, drain a small amount of coolant from the fill or petcock to prevent spills. Unscrew the old sensor, apply appropriate thread sealant or tape to the new sensor threads, then install and torque to the vehicle-specific specification. Connect the new pigtail to the factory wiring harness and verify the gauge or warning light operation before driving.

• Allow engine to cool completely before starting work
• Drain minimal coolant to avoid mess and air pockets
• Use thread sealant rated for coolant systems or approved tape
• Test gauge or light after installation and bleeding cooling system

Will this sensor provide accurate readings for my classic gauge or warning light?

The sensor is engineered to match common resistance/temperature characteristics used in many classic GM gauge circuits, providing reliable input to the dash gauge or warning lamp when installed correctly. Because electrical systems and gauges vary between models and years, confirm the part number cross-reference for best compatibility and accurate readings. It is an aftermarket replacement intended to restore standard operation rather than modify gauge behavior.

• Designed to interface with original gauge circuits or warning lights
• Restores sensor-to-gauge communication when original parts fail
• Not intended to change gauge calibration or alter electrical systems
• Buyer should verify OEM number matches for correct resistance curve

Who is this for: The Formiden G1852/12334869 kit is ideal for classic GM owners, restorers, and mechanics working on Chevrolet, Buick, Pontiac, Oldsmobile, Cadillac, or GMC vehicles built roughly between the 1950s and 1970s. If you are replacing a brittle connector, correcting intermittent temperature readings, or completing a restoration with period-correct replacements, this sensor and pigtail harness provides a practical, easy-to-install solution. Always verify fitment using the listed part numbers and your vehicle's repair manual before purchase and installation.