My Rheem furnace was working fine, it heated great...

My Rheem furnace was working fine, it heated great. The only problem when it reached temperature it wouldn't come back on unless you turned the switch from on to off, and then back on again.Then heated great.Isaac came out charged me $288.31 and left me with now NO heat and said I needed a new furnace.I have a friend in the business whom at the time was on vacation and I called when he came home. He plugged in all the connections that Isaac pulled out, and I had heat again! He told me please don't ever call Isaac again, they always try to upsell. My friend blew the dust out of a small furnace hose and I no longer have the issue of the furnace not turning back on by itself! Read this and BEWARE!!