Fan runs constantly

[richard.mockler]

I have a Toshiba r835 laptop with SSD with Windows 10 and Linux Mint 18.3 installed.  When either Windows or Mint is running, the computer is silent.  It can run for hours without ever hearing a fan. I installed Linux Lite 4.0 as a third OS, apparently with no problems, but now when I boot into Linux Lite, the fan instantly starts running, noisily, and never stops.  If I immediately reboot into Mint or Windows, the fan is absolutely silent. I have no idea what is causing the noisy fan while running Linux Lite only.  It can't be causes by overheating or excess dust, because there is not fan problem with the other OS.  This morning I first booted a cold machine into Linux Lite and the fan immediately started running.  Can someone possibly give me some help with this?
Thanks, richard.mockler