Blower motor help

83 300d
This week my blower just quit working "most" of the time for heat. Will come on for A/C and in the defrost mode (but not for hot air defrost). I have searched this site and found references to a thermal cut off to keep cold air from blowing in until the car warms up but I can't find anything like this on my car. Also references to a control box inbound of the power brake boost on the firewall under the hood which I also do not seem to have. Am I looking in the wrong place?
I don't think it's the control buttons because when I push for heat I can hear something click and vacuum controls working. The water pump also clicks on and starts to run and hot water will circulate through the heater core. Just no fan except for once in a great while it will kick on for a minute or so. When it comes on the high low buttons also work as they should. I have replaced the fuses in the fuse box and looked but not found any others. I also noticed the relay for the A/C compressor under the hood and am wondering if one of the two in that box control the fan motor? Not that heat is all that important here in Fl but I don't want it to become an issue with the A/C when it's needed in a week or so.