Macbook Air 2014 will no boot fan spinning only

[davg]

I have a Macbook Air 2014 that will not boot just the fan spinning at high speed? I have it from a lady who left it running for some time on her bed and when she returned it was shut down and wouldn't restart. What I have discovered so far is that by disconnecting the battery, plugging in the Magsafe and holding the power button for several seconds the fan will start spinning at high speed??. Even though the battery is disconnected the magsafe light goes from green to orange as if charging? The unit will not boot no chime no video just a fast spinning fan. Resitting the SMC and there is no response from the power button at all until I go through the process of again disconnecting the battery plugging in the magsafe and holding the power button for several seconds?? My best guess is that it over heated and may have damaged a Thermal Sensor?? Does anyone out there care to diagnose these symptoms? How can I check these sensors? I do have a schematic.