1993 oldsmobile 98 fan motor works but no air flow anywhere

Sounds to me that you might have a leak in the line. Those heaters are all Vacume actuated.

Ok, here is my take on your problem. As you may already know, it takes a car a few min. to actually warm up to operating temp. When the coolent reaches operating temp. the thermostat opens to circulate the coolent in the radiator. Now, as your drive, the air pushing against your car will actually blow some air through your heating system ducts and into the passenger compartment. Is it possible that your blower fan isn't working? Because while you are stopped, there would be no air forcing its way through your ducts, thus no heat. As your drive, your car gets up to operating temp, heats up, and the air pressure as your drive will blow some heat out into the passenger compartment? On a side note, if your thermostat is stuck in the open position, it would take it forever to warm up since it is circulating ALL the coolent even tho it isn't at operating temp. A thermostat stuck open will take 30 min or more before you actually feel any warmth, if at all in the winter.. your thermostat opens and closes constantly as the engine is running to keep it at its normal temp, usually around 160-180 degrees. If you live where it gets really cold, a thermostat stuck open likely will never get warm. If your blower motor works, and your engine don't overheat, im 98% sure its your thermostat.

ok the heater cor needs to bet hot, if not , no heat.
you can put hand on both tubes, of the core of any car.
do so, are the they both hot.
no, (the heater valve is closed or packed up, (no service? every 2 years)
yes then the heater, controls are bad, (bad controller or the damper flaps , motors (or cables, vacuum) controls are malfing.
lets do the flow (no pun)
1: hot engine, 180F holding or more.
2: fan blows
3: hot water flowing through the heater core....
4: dampers in the right position.
just 4 checks, find the one that fails in this order and the job
is less work, and to the real cause.

id didnt go to alldata.com to look at what type of controls you have.
we can, (so can you) if test 3 passes.
some cars have core valve , find yours and make sure it flows.
other cars there is no valve. and only the dampers block heat.

Sounds like the blend door or blend motor is not functioning/opening. This door allows the heat/cold air to come in by adjusting open, closed or anywhere in-between for temp. Start there. They are usually vacuum controlled and mounted under the front dashboard near the knee board.

Run the engine up to temp and let it idle (best, in gear holding the brake just like when you are in traffic). When the temp duplicates what you see during times when it's too hot, put it into park and check the electric fan(s) to make sure they are on. Also check the clutch on the mechanical fan. (turn the engine off to do that and immediately try to turn the fan. It should offer reasonable resistance to turning when compared to how it turns when cold. If everything checks out as good, Make sure there are no obstructions to air flow through the AC condenser on the front side of the radiator (visible through the grille). If still everything is OK, flush the radiator. It's possible that you have a slight obstruction to coolant flow. Most Jeep radiators are a bit too small for the application and therefore sensitive to restrictions that in a larger unit, would not matter much.
Your air conditioner adds extra loading on the engine and also adds heat to the air flowing through the radiator. When in motion, you actually don't need fans as air flow is far greater than a fan can supply.
When standing still, coolant flow and air flow need to be near perfect to keep the temp where it needs to be.
If you do flush the radiator, when re-filling do that with the heater on high so you don't get an air lock in the system. Also make sure you run the engine long enough for the thermostat to open so you actually fill the entire system. Use a hydrometer to establish a true 50/50 mix to prevent boil-overs.
(even cheap ones are reasonably accurate)

The heater door is probably stuck in the full heat position. It could be a problem with the heater door motor or the controller - you'd have to check for both mechanical and electrical problems under the dashboard.

you dont say if its Auto temp or manual???the "air temp motor" is up and to the left above the blower motor. you should see/hear/fell it move when adjusting the temp cold to hot. if it does not move it may be bad, or the door stuck. Usually the gears strip and you will hear a rythmic clicking sound from it. to check the signals its too involved to get at over the pc, so it could involve the a/c control unit. It may be better money spent to pay a shop and correctly diagnose the car.

Check the blower motor speed control resistor pack is ok.
(The resistor pack is usually located in the blower fan ducting in the air flow).
Check condition of electrical connection terminals on the blower motor circuit - these terminals pass considerable current and over time may fatigue overheat and loosen.
Check operation/replace any blower motor control relay,
Check the blower motor will run if +12v directly applied to the blower motor.
Check operation of the blower motor speed control switch is ok.

replace blower control module

There is a valve on one of the heater hoses that allows heated water to flow through the heater core when you select heat. With heat selected and car warmed up check to see if both of the hoses feel warm. If not then water is not flowing through heater core and valve may need replaced or heater core is stopped up.