new timer dail, still doesnt move

hello all, new to the forum with a dryer problem. my dryer timer will not advance while the dryer is running. i replaced the timer switch with a new one but i have the same problem. it does this on all settings. the dryer heats and drys normally. i pulled the back off and there is no sign of burns or melting of any sort. any ideas what the next part i should replace should be. dont want to keep throwing darts but dont want to call service if at all possible.
thanks,
jon