fancontrol: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/sbin/fancontrol - from package: lm_sensors

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/sbin/fancontrol - from package: fancontrol

You may install the required package with command apt-get install {package}

Error in other languages:
fancontrol: bevel nie gevind nie
fancontrol: comandă negăsită
fancontrol: comando não encontrado
fancontrol: commande introuvable
fancontrol: command not found
fancontrol: käsku ei ole
fancontrol: không tìm thấy lệnh
fancontrol: komanda nerasta
fancontrol: Kommando nicht gefunden.
fancontrol: kommandot finns inte
fancontrol: komut yok
fancontrol: nie znaleziono polecenia
fancontrol: níor aimsíodh an t-ordú
fancontrol: no se encontró la orden
fancontrol: no s'ha trobat l'ordre
fancontrol: opdracht niet gevonden
fancontrol: parancs nem található
fancontrol: perintah tidak ditemukan
fancontrol: príkaz nenájdený
fancontrol: příkaz nenalezen
fancontrol: команда не найдена
fancontrol: командата не е открита
fancontrol: 命令找不到
fancontrol: コマンドが見つかりません