Intermittent elec. problem NO HEAT below zero!!!

I have been jump starting my car for a few days and the heat sometimes works. I think I have a relay or switch out as heat has started and stopped several times. (A/C won't work unless you disconnect the batt. then only for a short time) I cannot find anyone who does not think I am nuts... Heater core has hot hoses and engine holds steady @208deg. I had heat the other day for several hours THEN I put in a new battery (10min) and no heat. I do have the 88 lss package with all the auto controls. Thank you for the help. Steve

Welcome to AF, post the year and do you mean no blower?

Sorry about the lack of info. I thought everyone knew what kind of car I drove..... I have a 93 88 LSS all the auto stuff. I have everything working BUT the heat, (blower works fine) Just found another fusebox on the passenger side. Actually thinking it might be a relay in the automatic setting for the temp, or a maxi-fuse? Thanks Steve

Correct, if the setting is for hot and the air comes out the proper heat ducts, the temp door may be disconnected or stuck, if the setting is is for heat and the air comes out the upper vents than the programmmer/control head can be at fault.There are also sensors in the system that can cause this issue.