I'll try my best to describe the issue and background of this furnace. It is my Aunt's and I'm trying to help out.

First off, the control Board was replaced 6 years ago, and the furnace is approx 15 yrs old. The thermostat is approx 1.5 yrs old., and a new digital style.

The furnace will kick on as it should and start to blow for 30-60 seconds, then shut off for no reason. We turn the master switch on and off to reset with the same result. Turned the Thermostat down for 5 minutes, then back up to 70, from the 61 it was inside the house. The furnace started up as it should, then 30-60 seconds later turns off again. After 30 minutes we gave up and went upstairs.

Now the weird part, another 30 minutes go by and the furnace comes on, stays on until it hits 70 in the house. Back to working properly. I leave my aunts, and 2 hours later she calls to say that it is 65 and the furnace is coming on, then back off again like it was before. This was last night around 8pm. It is now 16 hrs later, and the furnace has not come on properly again.

Any ideas before I go there after work tonight? I'm handy, but by no means a HVAC wizard.

Thanks for your help.

 

If the main burners light and the blower comes on, then shuts down, it may be a high limit switch.
First, check auntie's furnace filter. If it is old/dirty, it could restrict the air flow over the heat exchanger which could cause the furnace to overheat and trigger the shut down.