Miel I is a 188 m high RCC dam that was instrumented with more than 600 devices. The main idea of this instrumentation net was to monitoring dam conditions during construction and operation. Moreover, one of the main instrumentation goals was to control all the devices from the main computer installed in operational control room. Unfortunately, the contractor in charge of this labor was unable to finish the work and not all the devices can be inquired from the main computer. Additionally, the net started to suffer a progressive collapsed, especially multiplexors and datallogers and some instruments such as strain gauges and thermocouples with apparently no reason. For the next couple of years, the dam maintenance group executed routines with the aim to conserve the current instrumentation. However, at one point, the maintenance and replace devices routines were unsustainable and the instrumentation net could be in jeopardy. For that reason, the maintenance group decided to investigated the reason or reasons of the devices failure; finding that the instrumentation net was installed ignoring provider electronical recommendations, lightning protection and electrical isolation. In addition, the maintenance routines were conceived from the geotechnical point of view ignoring the electronical implication that a net like this one required. These problems are aggravated due to tropical conditions and light storms frequency. With this panorama, the Miel I maintenance group redesign the routines, manuals and maintenance periodicity using this new information, problems and findings.