Rumba v1.2g, E3Dv6 hotend, TEMP_SENSOR_0=5... still wrong temperature

hi some advice appreciated: i'm doing a corexy folding printer, and using a Rumba v1.2g with an E3Dv6 hotend. the configuration page for E3Dv6 says use TEMP_SENSOR_0=5, which i'm doing... and the temperature reads 40 degrees when it should be 25. with the thermistor disconnected the temperature reads 37.5 or thereabouts. also, the NTC EPCOS 100k printbed resistor (TEMP_SENSOR_BED=1) is the same deal: 37.5 ish when disconnected and a 40 degree reading when it should be 25.

this is with the following commit from https :// github.com / MarlinFirmware / Marlin.git

commit 122bdd187f9df02a6d9b59495630e40da307e82c
Merge: 9045ea3 f394c06
Author: Scott Lahteine 
Date:   Fri Mar 25 01:15:38 2016 -0700

    Merge branch 'RCBugFix' into RC

anyone any clues?

many thanks.