Just at Tightening the Hotend stage of commissioning after setting X Y and Z home etc. I can set Hotend "1" to 285 on-screen but it says Hotend 2 is increasing in temp. Both fans start at 40oC (should BOTH start?) Hotend 2 got to (on screen) 195 ish then got a "heating Failed" message. Using a laser temp sensor thingy NEITHER block that holds the nozzle appeared to be above ambient. Placing my hand behind the hotends air is COLD coming out. BOTH fans stop when temp drops to 40oC (as expected) .Just about to check the voltage on HE0 and HE1 pins on Rumba to see which if any have volts but as I have tried Hotend 2 and Hotend 1 (on screen) heats (set to 60) but it runs away way above 60 and keeps going and then I get Heating Failed then I don't want to have it switched on too long as although I can't feel or measure heat from outside something is heating and causing fans to start. Possibility is that I have the temp measuring thermistors the wrong way round as something appears to be heating.