1998 Navigator.

Noticed that the truck only blows hot air, doesnt matter what the temperature setting is, hot, cold, A/C on or off. It's hot.

When A/C is on, the lines are cold, so that tells me A/C is working, first thought it wasnt...

Is there a heater core valve on these trucks? I'm thinking it's stuck open or something....I read a couple places they dont have them, what else could it be??? It's getting hot out and heat is not required until Fall time lol.

 

From what I know being here, you are describing symptoms of a broken blend door or failed blend door motor. But first, questions:

1. Do you have rear air (I'm assuming yes since its a Navigator)? Does the A/C blow cold in the rear vents?

2. It might be that the temperature control **** is worn out. Mine was and I couldn't control the temperature in my 97 Expedition. Its a simple test using an ohm meter to determine if its working or not. I have a post that I'll find for you. I switched mine and wha-la, all was fixed.

3. Is air only blowing out of the defrost vents? I believe that is another indication of the broken blend door because since the door is broken, obviously you cannot direct the flow of air.

Check out my old post:
https://www.ford-trucks.com/forums/8...lend-door.html


The temp control **** is an easy fix.

The blend door motor, IIRC, can be changed without too much hassle.

The blend door on the other had requires removal of the dash and draining the A/C refrigerant, etc. and is a pain. If you go this route I recommend buying one of those kits with a metal door that is fixed buy cutting a hole in the plenum box and replacing the door from above rather than removing the dash.

Let us know what you find.

 

I think you meant "heater control valve". I looked it up for you on rockauto.com it says the 5.4 has one. usually they are line with the heater hoses. I would check that first.

*maybe the people saying they did not have one did not have AC in there vehicle?

 

if it did end up being the blend door there are some ways of fixing it with out pulling the dash. a company called heatertreater.net sells a kit for about $130 and then if you do a search there are some people that show how ot do it the same way but you just buy a replacement door for $20,,,. I have not had to do it myself so that is the best I can help you

i am suspecting something is up with the heater control valve....let us know what happens

 

I'll check the rear air.

Yes, heater control valve is what I meant.

The temperature **** isnt a ****...it's digital.

It goes from vent, defrost, floor. I dont think the blend door is at fault.

 

There is no rear air controls. Just the ability to control airflow (no temperature) on the rear of the console.

I suspect the heater control valve is faulty, stuck in open position so heater core is always hot. Where abouts is this valve in the engine bay? This is my Mom's truck so I'm not quite sure where things are located since I havent really looked under the hood of it before. Explorer no problem. I've done a few over the past years I've owned them.

 

as i said in my earlier post I dont own one of these, however I looked on rockauto.com and it shows one that looks like it goes in the heater hoses.. o to rockauto and see wha tit looks like then go to your truck and follow the heater hoses you should see it