My trane heater ignites then goes off it does this 5 times then blower goes on with out heat where is the heat sensor located

I think you may be looking in the wrong direction. I had this prblem a few years ago and it was the main gas valve that went out. Basically your ignitor is lighting and looking for the gas and when the sensor on the left and right don't see the flame it tries again. Your fan keeps running as a safey feature. The valve I think was about $100 wholesale. It is not too hard to put in... just take your time and make sure you have all the right tools and equioment. And ALWAYS check for leaks with the bubbles around your fittings

The flame sensor is located at the left end of the burner manifold, if it is defective, and doesen't sense the flame it shuts the gas valve which leaves you with a blower pushing cold air.My xe80 will start sometimes and sometimes it just doesen't send the glo-bar{igniter} any current and the fan just pushes cold air.