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Our M20 X 1.5 stainless steel coolant level sensors were originally designed to replace the plastic OEM upper and lower sensors that began to be installed on transit bus engines in 2013. We first saw them and characterized them during the implementation of our 1/2 NPT stainless steel upper coolant level switch on NABI buses at New Jersey Transit. Our first large scale campaign occurred at MARTA in Atlanta on 265 New Flyer CNG and 105 diesel buses. MARTA continues to install our sensors on all new bus deliveries from Gillig after removing the plastic sensors during Post Delivery Inspection (PDI).
Another sensor part number we offer is our VT220594-FZ to replace the 3 or 4 wire capacitance style sensor being installed by many of the OEM Transit Bus Builders. These sensors have the opposite failure mode of the plastic sensor meaning they will have a false negative mode of failure instead of a positive mode. When components of the extended life coolant form a deposit on the teflon probe of the sensor, the sensor will indicate the presence of coolant when it is not there. This means the sensor may not alert the ECM that the surge tank is low on coolant. The next line of defense is the high limit temperature sensor and that delay in shutting down the engine may lead to further damage.