1977 Buick blower / fan comes on however NO heat blower / fan also blows very low.

Generally they are located inside the air duct so that the cooling air from the blower keeps the resistors cool. Some vehicles have a cover over them that enables you to remove them without removing anything else, while some vehicles require the whole blower and duct to be removed to get access. If there is not a small cover located somewhere under the dash in the ducting, then most likely your one requires the whole thing to be removed.

Sounds like high blower relay is bad

Sounds like the Blower Motor Resistor. The range from 10 to 75 dollars depending on what kind of vehicle. Pretty easy to change.
Blower Motor Resistor Repair Heater Fan Speed Control Chevy Blazer GMC...

It's the switch in the control panel. Would you like instructions for replacing it?

The 1992 was prior to Buick putting cabin air filters in so there is not a possibility it is clogged. So more than likely your blower motor is going bad or your fan control switch is bad. Does this problem occur with heating as well as AC? Does it change if you switch between blowing on floor, face, window(defrost) If it doesnt change based on location of blow and type of air temp then I would start by turning fan on high and placing head (ear ) against dash in center of console area. Have someone turn fan knob from low to high with engine OFF...After goign from low to high and back a few times you can see if the blower motor is responding to signal from switch. Listen for a whine, squeal, rattle, or humm. A whine or Humm would indicate a bad blower motor... Squeal or rattle a bad squirrel cage/fan blower blades. If you hear no noise and no perceivable change in blower speed/noise then its possible your switch is bad. Unfortunately the only way to definitely diagnose either is to pull the switch from dash and use multimeter to test for voltage change and for blower motor to pull dash. There is a digital control unit for your car as well. Although rare sometimes the wires on this can loosen or it can go bad. But since you didnt state teh fan wasnt working at all and you are getting cool air, that woudl be teh last thing to check

Check your vacuum lines. Does any air blow out at all? Is it push button, or have a slide? Could also be a bad cable.

I would recommend a salvage yard to get a good used one alot cheaper also try this place they carry only GM parts: Schram Auto and truck parts 1-800-292-1032 and also explain to them the problem you are having and these guys can assist you in getting the right part

it's either a fuse or it's a bad blower motor, it could be a bad blower motor resistor but usually you'll get either high or low only, so if you have nothing on any speed, high low etc, and all the fuses are ok chances are it's your blower motor.

it's either a fuse or it's a bad blower motor, it could be a bad blower motor resistor but usually you'll get either high or low only, so if you have nothing on any speed, high low etc, and all the fuses are ok chances are it's your blower motor.