1991 Privia LE Heat does not work. Air is circulating but is cold. Any other possibilities besides the heating core?

There are several possible reasons why you may be experiencing cool or no heat in your 2002 Jeep Grand Cherokee Laredo after replacing the thermostat and bleeding the air out of the lines. Some possible causes could include:

1. A malfunctioning blend door or actuator: The blend door controls the mix of hot and cold air that is directed through the heating system. If the blend door or actuator is not functioning properly, it may cause a lack of heat.
2. A clogged heater core: The heater core is responsible for transferring heat from the engine to the cabin of the vehicle. If the heater core is clogged, it may not be able to transfer heat effectively, resulting in cool or no heat.
3. A faulty thermostat: If the thermostat was not properly installed or is not functioning correctly, it may cause the heating system to not work properly.
4. A problem with the water pump: The water pump is responsible for circulating coolant through the engine and heating system. If the water pump is not functioning properly, it may cause a lack of heat.

Most likely it is the heater control valve that shifts air from blowing across your heater core to your air conditioner core.

If your fan works and your car is fairly new..meaning your heater core isn't dirty and full of craap...then it is the climate cotrol valve.
If you are lucky, it might be a thermostat that is bad and blocking hot water from entering your heater core. Bottom line, if hot water doesn't circulate thru that little heater core, you won't get heat.
You might be able to look under the hood and grab the hot water lines that go thru the firewall and feed your heater core. If they feel cold to the touch after engine has warmed up, then you aren't getting circulating water to the heater core. If they feel nice and warm, then the heater core is fine, but your climate control valve has closed off the fan that blows across the core to disperse heat into the cabin

The complete removal is shown in this youtube video.
http://www.youtube.com/watch?v=vLdMYx6fhic

So you're getting heat but no blower to circulate the heat, right? It's also possible the fuze is blown to the blower motor, the switch that adjusts the speed of the motor could be damaged, or its resistors that limit voltage, to control speed could be "open" (burned up). I would check many of those before replacing the fan..

The heat is controlled by a valve that allows water to circulate through the heater core. If the fan is blowing cold air, check the valve, or blow water back and forth through the heater core to clean it out.

the engine is working fine, there is no heat. the coolant is not circulating into and out of the heater core. so you have a circulation problem.

1) there is an air bubble in the core,
2) there is a bad valve in the heater hose operated by the switch which turns the heat on,
3) or the heater core is plugged.

work on those , probably the last one as it is most expensive and difficult to repair.

With your front heat working the most likely cause for the rear heat not to work is that there is an obstruction in the line that is preventing the warm coolant to get to the rear heater core or the rear heater core itself is plugged and not circulating. Another possible cause could be low coolant level where the system has enough coolant to provide the front system with enought warm coolant but not the rear system. Hope this helps

the heater core is plugged.you will need to replace it.

If you have good heat on one side, it can't possibly be the the thermostat. Good heat on one side means that there is plenty of hot water (water and antifreeze mix) circulating through your heater core. The thermostat controls the temperature of the water. If you have hot water, the thermostat is not at fault. Your Impala is equipped with what is called "zoned climate control". All the inside air (both sides) is still heated by the same heater core. The difference between a "zoned" system and a conventional system is that there is more than one "blend-air" door insided your HVAC housing. The blend-air door swings back and forth to direct the incoming air either through the heater core (for hot air) or around the heater core (for cold air) The drivers blend-air door may be broken or the motor that moves the blend-air door is malfunctioning.

hello.....
first in this problem you need to look for cheapest things to do which is start with you thermostat abd make sure its open and close by how much temp inside the eng. then u need to feel the input hose and the output hose which they come from the heater core they should have closely same temp . if there is non of them have any heat thats mean the water pump blower is broke and u have to replace the water pump, if one of the heater core hose hot and the other cold the problem in the heater core , about the A/C light is on the A/C comprasser shoul work with the heat becuase hot air + cold air = dry air which u need for ur front DEF

Generally when the heater isn't heating anything and putting out cold air the heater core is bad. I have never worked on a BMW before and have never heard of a heater core causeing overheating, but because they are linked, it maybe a clog in the core causing poor coolant circulation.

I had the same problem in my 1991 caddy, and turned out to be the blend door. It is located in back of the glove compartment. There are two kinds, the automatic blend doors and the manuel ones. Since the temperature is automatic and programmed to stay where it is set, it would be an "automatic blend door". Not a hard fix...