Well today my Volt had the dreaded no heat! Coming home the seat heaters kept me warm but I wanted warm air, no luck hit OnStar and their help desk was less than helpful. So I read the post no avail, so I got thinking computer car time to reboot! Pulled out the manual pulled all the htr fuses and just reseated them. Since it worked with bluetooth problems I thought it would work for the heater. I pulled the two in the engine compartment and turned them and re-seated them. Then I pulled F5 in the passenger compartment. count from the bottom its number 5. When I re-seated it the car made noises like it was moving the air baffle in the HVAC system. Turned on Karma (my Volts name) and guess what warm air in under a minute! I was worried that I had something burned out, and I did not want to wait for parts or have it in the shop! I hope this helps with the heat issues. My heater worked last night great then not so much today if it is just a reset issue they should be able to write code for that.

I hope this helps everyone!