My furnace won't stay on. It will kick on if I shut the thermostat off then back on to heat again, but it never reaches up to the temp the thermostat is set at. The furnace will start by itself, but does not get up to temp before shutting off which is to say that it gets to a certain temp then seems to go through the "cycles" several times before shutting off altogether.

OK so after some self-diagnosis, I THINK I have it (Keep it mind I am NOT an HVAC guy nor do I pretend to be!). After reading the fault codes on the panel, I believe it to be the Limit Switch. I have now bypassed the switch with a jumper wire and it ran all the way up to... and PAST the thermostat temp! Is it possible that the thermostat could be bad too? What are the odds?

Shorted thermostat wire could cause this. DO NOT leave the limit jumped out! You are running without protection. Make sure all registers are open and the filter is clean and the return air is not restricted. Something is causing it to overheat and you better be finding it.