If both heater hoses are HOT to the touch with the engine at normal Operating temp.

The heater core is fine.

How is the air flow out the floor and defrost ducts ?

 

i will have to check later, but on high it doesnt seem as powerful as I suppose it should be or it sounds like it is going at

 

ok the heater hoses are hot both of them so what would it be?

 

I'm having the same sort of problems on my truck. Both hoses are equally hot but i don't seem to get hot air to blow out.

 

Does your truck have AC? If so, maybe the blend door is not sealing completely or mayb the foam seal on the door has turned to dust. If you don't have AC, it could still be a blend door problem. Also, check the vacuum motors which pull on the blend doors. If the blend door is not sealing completely closed, you aren't going to get the hot air that you should.

 

yeah I have AC, does anyone have a diagram for it? I kinda figured maybe a door is getting stuck or something, the foam is non existent i believe now lol

 

mine has an aftermarket A/C and i had others tell me to check the doors. unhook the cable running to them and be sure they are allowed to move completely to one side or the other

 

Here is what it looks like.

I also have the instructions for where air should flow when the control is iin each position

 

is that the instructions or not? cause that'd be useful too lol

 

Instructions

2 pages.
this is page one or two

http://i69.photobucket.com/albums/i7...Operation2.jpg

 

With A/C, there are three possible reasons why not enough heat comes from the registers.

1) D4AZ-18495-A .. (Motorcraft YG-136) Heater Temperature Control Valve-Vacuum Operated. Fits: all 1973/79 F100/350's and all the cars 1971/78 with A/C.

This is an inline water valve, spliced into the heater hose, and has been a POS since day one.

Here's what happens: It's stuck.

When stuck in a partially open position, it will not allow enough water to flow to the heater core. When stuck in the closed position...no water flows to the heater core.

2) A blend door vacuum motor may be defective. Autoparts stores carry a universal fitzall that can take the place of the originals (there's several).

3) Both the blend door motors and the POS vacuum heater water valve are controlled by the multi-ported:

A/C Heater Vacuum Control Temperature Valve which mounts behind the control panel on the dash.

When the lever of the control panel is moved, this part opens one blend door, and closes another by way of vacuum.

You may hear a hiss when the valve operates. The hiss sound means = it's leaking.

This part also has the "kicker" switch on it to turn on the A/C compressor.

D5TZ-19B888-A (Motorcraft YH-285) Fits: all 1973/79 F100/350's and 1978/79 Bronco's with factory A/C.

Either the vacuum lines from this valve are cracked, or the valve itself is defective = typical...so what else is new?

Both the POS heater water valve and the A/C multi-ported valve are still available from Ford.

D: Section 195 / pages 17 & 18 show the 1976/79 A/C heater parts (1973/75 is similar). The part marked 18502 shown on the control panel is actually part number 19B888. 18502 is only used WITHOUT A/C.

 

well I do hear a hiss all the time when i turn the truck off, so what exactly is leaking then? process of elimination i guess