Hot coolant not getting to Heater Core.

Low coolant, if there is an air pocket in the engine it will make it to the heater core. Once there , the air coming out is cold/cool. Once the coolant fills the heater core, it gets hot. If the coolant is fine hot or cold, then have the HVAC system scanned.

There a a couple of possibilities

1. The thermostat is stuck open. This can usually be veried by looking at the temp gauge. If it is not about half when after the engine has had enough time to fully warm up than I would suspect a bad thermostat.

2. the coolant level is too low. The highest point in the cooling system is the heater core. If the coolant level falls to low the heater core will not get enough hot coolant to function properly.

3, the heater core is plugged. Proper cooling system maintenance will remove much of the debris that ends up in the cooling system. If this service has been neglected this debris will settle in the heater core. Over time it will build up to the point that hot coolant can not flow through the entire heater core resulting in less than adequate or no heat.

4. The last possibility (and the least likely) is that you have a head gasket failure. The air that gets pushed into the cooling system will cause an air pocket in the heater core restricting the coolant from entering.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

OPERATION
The primary purpose of a cooling system is to maintain engine temperature in a range that will provide satisfactory engine performance and emission levels under all expected driving conditions. It also provides hot water (coolant) for heater performance.

Fig. 1 - Cooling System Operation - 2.0L/2.4L 1 - HEATER 2 - HEAT UP 3 - COOL DOWN 4 - PRESSURE CAP 5 - COOLANT OUTLET CONNECTOR 6 - WATER PUMP 7 - ENGINE 8 - COOLANT RECOVERY CONTAINER 9 - RADIATOR

Fig. 2 - Cooling System Operation - 2.7L 1 - HEATER CORE 2 - COOLANT PRESSURE CONTAINER 3 - COOLANT OUTLET CONNECTOR 4 - ENGINE 5 - WATER PUMP 6 - THERMOSTAT 7 - RADIATOR

I think the previous owner needs some heat--inspec system-the vacuum controls on the panel cud hav issues or the heater door or the core itself--get a repair manual from fixya or a parts place

hi Planeman.
Why is the heater in my car not working? Ken Mattson, owner of Len's Automotive in Bellevue, Wash., says a car heater can stop working for a number of reasons, including: A low antifreeze/water level in the radiator due to a leak in the cooling system. A bad thermostat that isn't allowing the engine to properly warm up.11 Dec 2013

Why Isn't My Car Heater Working? ' Angie's List

https://www.angieslist.com/articles/why-isnt-my-car-heater-working.htm Search for: Why is the heater in my car not working?
Why is my car heater not blowing hot air?Hot coolant from the engine passes through a heater core, which looks and functions a lot like a small radiator, and a blower motor forces air through it. ... It's also the reason that a plugged heater core, stuck thermostat, or air in the cooling system can all cause a car's heater to blow cold.9 Jul 2017When Your Car Heater Blows Cold Air - Lifewirehttps://www.lifewire.com/when-your-heater-blows-cold-air-534667
How do you fix the heat in your car?Begin with the vehicle on level ground, engine off (cold) in park with the emergency brake set.Heater Controls. Step 1 - A heater cannot operate unless the engine is full of coolant/antifreeze. ...Refilling Cooling System. ...Engine Thermostat. ...Blend Door Actuator. ...Broken Vacuum Line. ...Heater Control Valve. ...Vacuum Gauge. ...Heater Core.How to Fix a Car Heater in Under 30 Minutes - 2CarPros
What are the symptoms of a bad thermostat?A motor with a bad thermostat will run fine for the first few minutes, then overheatrapidly. Other symptoms include the engine and radiator making a rumbling, gurgling, boiling sound: like a steam pipe knock, if you've ever heard one of those. A thermostat sticking open can make your heater not work in the winter.Auto, Car, Truck THERMOSTAT Repair bad thermostat symptoms
or go to this link if you need more help.
2008 ford ranger has heater that won get hot Google Search

There are a couple of possibilities.
1. The heater core may be plugging up. Dirty coolant and lack of coolant services can contribute to this. Backflushing the heater more resolve the issue. If it does have the cooling system flushed to remove the rest of the contaminates from the cooling system.
2. The coolant level may be low. The heater core is usually the highest point in the cooling system. If the coolant where to get too low the heater core would starve for hot coolant at idle.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

good day, heater core/coil is leaking antifreeze and needs to be replaced. The heater core works in conjunction with your engine's cooling system. The function of the cooling system is to remove heat from the engine, and it does this for the most part by sending the heated anti-freeze to the radiator located in the front of the car. The position of the radiator allows outside air to blow across the radiator thus cooling the anti-freeze. The anti-freeze is then sent back to the engine. Hot anti-freeze is circulated throughout the cooling system by the radiator and heater hoses. Think of the heater core as a small radiator located inside the dashboard of your vehicle. hope this helps, have a nice day.

First check your radiator cap to make sure theres no pressure escaping. The cooling system needs pressure to push the hot water to the heater core. You also need to look at your heater core itself. With the engine running touch the lines coming in to the heater core through the firewall. If they're both hot you may need to replace the core, if only one is hot you've got a blockage in the cooling system preventing the flow to the heater core.

Check operation of the heater core coolant control valve and associated remote control mechanism.
Chech heater coolant hoses are not kinked or crushed,
Check that both inlet and return heater hose is equally warm, as this indicates coolant flow through the heater core.
If no coolant flow:-
Check cooling system is correctly filled, taking care to bleed off any air locks from the system as necessary (with heater coolant valve open);
Check heater core is not blocked- if blocked you may be able to backflush.

Try this link for a free manual:-
http://safemanuals.com/user-guide-instructions-owner-manual/OLDSMOBILE/ACHIEVA%201998-_E

The heater in your car depends upon a flow of hot coolant going through the heater core in order to get hot air into the car. If the heater core is partially plugged, it will restrict the flow. If you have a head gasket that is putting exhaust into the cooling system, it will eventually get into the heater core. When this happens there is no coolant in the heater core to make the air warm. If the water pump vanes have corroded away the result will be very poor coolant circulation causing the heater to not blow hot air. If your car is equipped with a heater control valve that is not functioning properly, the coolant flow will be restricted. One or a combination of these factors is likely the culprit in your case.

if the car is not overheating, the thermostat is working fine.... replace or flush the heater core multiple times to try and eliminate sediment build-up.