Heater isn't working but thermostat is working properly. Any suggestions?

Hello! Thermostat should be a 190 degree...you may have an air blockage...Remove radiator cap start engine and leave cap of until all air bubbles are out (even after thermostat opens)...Cap and test for heat...if there isn't any heat...When that thermostat opens and hot water flows through the upper hose of the radiator that hose will be hot and hard..If you feel the heater hose only one will be hot which means that nice hot water is not passing through the heater core...That could be due to blockage or the control in the car isn't opening the valve on the core...check to see if the heat control is opening the valve...If it is, I would suggest that you purchase a back flushing kit ($10) A plastic tee fits into the inlet heater hose and a garden hose is then connected to the tee...Drain the radiator, remove the thermostat, and turn on the water...do this with heat control on high...The system will back flush out of the top of the radiator and hopefully clean the blockage...Reassemble ...Cap off the tee (cap is in kit)...Install thermostat (190) Is a better choice...Refill radiator...Start engine and leave the radiator cap off until all the air bubbles out............At that point you should have heat...Guru...Saailer

I’m happy to help further over the phone at https://www.6ya.com/expert/david_6df67de3b14de867

Without more information, I can tell you that you have a problem with your heater core. Check coolant levels and make sure you aren't low on coolant. If that isn't an issue, make sure your heater core isn't bypassed. In Texas, I see them bypassed instead of repaired because it hardly ever gets cold here. You could also have a dirty heater core that isn't allowing the heat transfer. The only other thing it could be is an issue with the temperature blend door/actuator. If it isn't opening properly to allow the warm air from the heater core to enter the ventilation system, you won't get hot air.

Here's a list of possible culprits:

Priority Action Part Type Cause
1 Inspect - Antifreeze Needed - Coolant Level Low.
2 Inspect - Heater Control Valve - Leaking or Faulty Heater Control Valve.
3 Inspect - Thermostat - Thermostat Stuck Open.

First thing to check is your engine coolant level - quick and free.
Since your blower works, my nominee for the offending part would be the Heater Control Valve, which redirects hot coolant into the passenger compartment heater core. Without hot coolant, the blower will just blow cold air, since the heater core isn't getting the needed flow of hot coolant through it.
There may also be a fault in the "Temperature Valve Actuators" (there is a right hand and a left hand version of these - one for each side of the car).
The Right hand Temperature Valve Actuator is AC Delco part #15-72971.
The Left hand Temperature Valve Actuator is AC Delco part #15-72972.
Their pictures are available in the online AC Delco Parts Catalog at:
http://parts-catalog.acdelco.com/catalog/catalog_search.php
Here are your parts search parameters:
Vehicle: 1996 OLDSMOBILE AURORA V8-244ci 4.0L F/I Vin C ID# 17739
Group / Subgroup: Heating/AC / Heater Core and Htr Control Vlv

sounds like you have a bad temperature door actuator. This is a motor that connects to the door and uses inputs from the sensor in itself and the heater control module to open the door from hot to cold. I does take some knowledge on recalibrating this actuator and installing it. if it isn't install correctly it could damage the new part, so just take care

Your problem can be caused by a bad thermostat, bad heater control valve, a heater door that's not opening or a clogged heater core. If the thermostat is good, check your heater hoses when the heat is on. Both should be hot; if one isn't there is a vacuum operated device inline with one of the hoses (heater control valve) make sure the vacuum line is connected to it. Sometimes you can manually force the valve to move; if you can do it and see if the 2 hoses get hot as a result. If they do, change the valve. The heater door is inside the vehicle and it too is usually vacuum controlled and often somewhat involved to service. I'm not sure of the exact configuration of your heater core but they too can become very involved to replace. More than likely the heater core isn't clogged and there's a very good chance you just have a sticking heater control valve.

Sounds like the compressor or the heater core.

It is probably a vacuum-controlled device; look for vacuum leaks under the hood or a ruptured vacuum reserve canister; the connectors are often fragile and break off.

Check the valve controlling the flow of coolant to the interior radiator.

I would check the thermostat first. It sounds like it may be stuck open.
On any of the newer autos pulling the front panel to access the heater controls is a major pain.
Start with the easy stuff first.

Good Luck, Duane

if the heater hoses are hot on both sides(indicating the engine is at full temp) and you feel the heat controller in dash is working properly, i would suggest disconnecting both heater hoses and backflush heater core with decent amount of pressure. if this improves condition but does not solve completely, heater core replacement is necessary.