Review on Standard Motor Products TS268 Sender by Jacob Sriubas

Manufacturer and Revain specs are incorrect. Incorrect part for Jeep CJ7 of any model year. The reason: The coolant thermostat determines the minimum operating temperature of the engine. If the thermostat is rated at 195F, 195F is the lowest operating temperature before closing. Fully open is approximately +15°F from nominal, so the range of interest is 195°F to 210°F. It is commonly believed that the thermostat opens to increase coolant flow to overheat the engine. That's not true, on the contrary. Most factory temperature sensors are designed so that the center line of the sensor is at the fully open thermostat position. In this case 210F. Per AMC Power Plant Instrumentation OEM Service Manual 1L-41, the full operating range of the CJ7 factory temperature sensor is 73 ohms (cold) to 9 ohms (hot) with green (operating range) 36 ohms to 13 ohms. As the engine temperature increases, the input resistance (Ω) received by the sensor decreases. Using the above, the factory temperature sensor centerline reading should be approximately 210 F, with a received sensor input resistance of 25 ohms. When I tested the TS268 sensor, the temp gauge showed a cold temp regardless of the engine temp. I measured the resistance between the center terminal of the sensor and the sensor body and got 2.26k ohms. I went one step further and put the TS268 in water heated to 210F and read 360 ohms. The resistance is 10 times higher than expected. Wrong sender. After thorough research and experimentation, the correct part number is Standard Motor Products TS37. Even if it says otherwise in the SMP Application Guide. 34 ohms Note that the output of the sensor is exponential and a change of 4-6 ohms will change the temperature you specified on the thermostat by up to 10 degrees. Your electrical ground needs to be perfect for your sensor to work reasonably well at higher temperatures. Otherwise it will always be colder than it really is. On my 1986 Jeep CJ7 TS37, the gauge needle should just go into the green operating bar (36 ohms) when the engine is at operating temperature (210F). That's exactly what he does. Hope that helps.