Better, now we know what we are dealing with.
There are generally two groups of conditions that result in the HVAC system being unable to deliver hot air.
First, on the coolant side of things, there are several possibilities that come to mind:
1. Lack of/reduced flow from the engine to the heater core
2. Improperly connected heater hoses (at either the engine or the heater core)
3. A lack of heat transfer in the heater core - to the air being delivered to the cabin vents. Due to excessive deposits on the watersides of the heater core tubes.
4. Engine coolant not reaching normal operating temperature.
In the air handling system, a no heat condition is usually caused by improper operation/control of the blend door.
I would check the easiest stuff first;
1. While mode control (where the air comes out) consists of a complex system of vacuum operated diaphragm motors and tubing, temperature control is accomplished by a simple control lever and a cable connects the lever to the blend door operating arm.
Crawl under the dash and verify that the cable from the temperature lever on the control panel to the blend door actuating arm is connected and free to move. As the temperature control lever is moved from cold to hot, note whether the arm moves along with the cable and strokes fully left to right:
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If that all seems okay, check that the blend door is actually being positioned by the action of the operating arm. There will be a little rectangular or round clip that keeps the loop on the end of the cable from popping off the pin on the arm. Remove that and release the cable from the pin.
(Hint: that little retaining clip can be a bitch to get off the pin. And often times when you do manage to get it off, it goes flying and is never seen again. The trick is to treat it as if it were a nut and the pin was a screw. While applying a slight upward pressure on the underside of the clip with a small screwdriver, rotate the clip in a CCW direction. It will bite into the pin and as it is rotated, it will begin to rise.
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When you get it near the top, it will pop off easily)
Now with the cable disconnected from the arm, use your fingers to manually stroke the arm all the way from left to right. Do this vigorously so that the blend door is caused to kind of slam up against the inside of the casing. If stroking the arm (which is pressed on to a shaft that drives the door) hard over from stop to stop, causes an audible thump within the air handler casing - you can assume everything is properly engaged.
If there is no thumping sound from the blend door hitting it's stops inside the casing, or if you somehow get the sensation that the door is slipping in relation to the movement of the arm...that indicates that the shaft that drives the door is no longer securely attached. It is secured to the door at the factory with some kind of epoxy that can fail. The result is that the door is free to float around wherever it wants. There is a modification - shown below - that you can do to fix this. But lets hope that isn't the problem:
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That is pretty much it as far as temperature control problems that are caused on the air handler side of things. Next check the coolant heater core system. First thing is to verify that there is sufficient flow throughout. Hot coolant leaves the engine from a nipple in the intake manifold - usually right next to the thermostat housing/water outlet. Yours might be in a slightly different location but as long as the heater core inlet hose is attached to the intake manifold - that is correct:
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The inlet hose goes into the heater core via the lower connection. THIS IS IMPORTANT. If the hoses are connected incorrectly, the core can become airbound and heat transfer capacity is severely reduced. These two images show the hoses properly connected to both a heat-only and A/C system:
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After exiting the heater core the slightly cooler coolant is returned to the main part of the system - generally the outlet hose runs to the radiator and is connected to a nipple that dumps into the radiator outlet tank:
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The litmus test for proper flow through the heater core is done by observing the rate of return into the radiator outlet tank.
With the engine cool, remove the radiator cap and temporarily drop the level in the radiator to a point a few inches below where the nipple enters the tank. You can use the radiator drain ****, a turkey baster through the radiator cap opening, siphon with a garden hose, whatever you find easiest.
Now, with the level in the radiator outlet tank a bit below the nipple, start the engine and let coolant flow through the heater core be established. This will happen almost immediately. Position of the temperature control lever does not matter.
Use a flashlight to look down the radiator cap opening and into the outlet tank. You should see a good flow of coolant literally gushing into the radiator. Rev the engine a bit and note whether the flow increases with engine RPM.
Do these two tests (blend door operation and proper flow through the core) and let us know your results. I know they sound long and involved, but they are really easy. It probably took me longer to write this than it will for you to conduct the tests.
