Have an old honeywell room stat (type with round temp knob) and have taken off wall to allow for decoration. Now heating does not work. Any ideas on whether it's broken or alternatively can it be bypassed.

Jumper red to white and it should bring on a call for heat. if it does then you probably damaged stat on reattachment. do you self a big favor and go to a digital stat. you probably have a red white yellow and green wire. hook them up same way on new stat. if you have an extra wire you can pull a common and power the new stat off the transformer, if not you can get one that uses batteries. robertshaw makes some good ones 9400 9401 etc. you need straight cool with gas furnace. they are great. no need to get to fancy and avoid the ones with programming and all. they are way to complicated unless your into lots of programming and tech details. plus those old honeywells are almost impossible to get perfectly level on the wall and if they are not level they will perform way out of whack