screaming heaters

[keri]

hi have a 1975 xjs with heater issues, first the fan speed only works on demist when the blowers really blow hard nothing on low or mid or high just demist posistion and secondly if i move the temp control a sreeching screaming noise from the heater box is heard for about 10 seconds car has been of road 20 years so this could have something to do with it anyone come across this before i would like to rectify these before interior refit.
thanks
keri