My ruud silhouette 2 will not heat up past 67 degrees. It is set to 72, and the filter is new
The furnace is 10 years old. It is 7 degrees out side. And it continualy turns on and off

Low gas pressure can cause this problem since the furnace will not run at its maximum capacity. The turning on and off could be a defective thermostat or a service problem with the furnace itself. If you have the proper tools and the knowledge to use them have at it if not call for On Site Service.