Tenant Complain of Temperature Difference

[Marie S.]

I have a tenant that is complaining that there is a 5 degree temperature difference from the bedroom and the living room. This is a one bedroom apartment in a 100 year old four plex. There is nothing mechanically wrong with the furnace. The technician cleaned the heat sensor just to make his trip worth while. The ducts have been clean. The windows don't seem drafty, but I may get the film for them tomorrow. Any  ideas what the problem could be?