Researchers at the University Transportation Center for Railway Safety (UTCRS) have developed an onboard wireless monitoring device to gauge the health of freight railcar rolling stock. A wireless system will allow for preemptive maintenance to occur, potentially saving millions of dollars in damages and ensuring the safety of passengers and cargo. A prototype energy harvester has been developed that can extend the battery life of the wireless monitoring device. It uses Thermoelectric Generators (TEGs) mounted on the bearing adapter to convert heat generated from the bearings to electricity. Previous results have shown that, under optimal conditions, TEGs have been able to produce enough energy to meet the power demands of low-power circuit boards. This paper summarizes the proof-of-concept validation of the complete energy harvesting device which includes the performance of the TEGs, heat sinks, boost converter, and the Battery Management Chip (BMC) working in tandem. The testing results were acquired by replicating field service conditions using a test plan that reproduces speeds encountered on a realistic railroad route and run on a laboratory dynamic bearing test rig. The test plan simulates a train completing a round trip between Billings, MT and Council Bluffs, IA. Preliminary testing results show that, over an average trip where train speeds vary, the energy harvesting system can significantly extend the battery life by producing enough energy to maintain or increase the charge of the battery while also powering the sensors and wireless transceiver for the duration of the trip.