"It is recommended that the FAA and EASA require the manufacturer, Boeing, to include in its Aircraft Maintenance Manual (AMM) for the DC-9 and MD-80, the Troubleshooting Manual for the MD-90 and the Fault Isolation manual for the 717 series of airplanes, specifically identified instructions to detect the cause and to troubleshoot the fault involving the heating of the RAT temperature probe while on the ground."
Not unexpected or surprising, this is the Safety Recommendation which the Spanish accident investigation board made already on 25 Feb 2009.
The full text can be found here:
http://www.fomento.es/NR/rdonlyres/8..._01_09_ENG.pdf
It is perhaps surprising this was not posted here at pprune earlier on. Shows perhaps how quickly serious things as this disappear from our radar screens.