Now that it's COLD in Mid-Missouri, the heat in the truck has left. It blows, but it is cold air. Both hoses are hot to the touch so I would think the core is ok. Where to look for a fresh air door stuck open?

 

now wouldn't that be a bad thermostat stuck wide open? Or low coolant which let air in the heater core. Might need a good flush as well.

 

Welcome fellow Missourian, ready for this snow storm tonight?

Ohh you have no heat.... guess not.

First thing I'd suspect would be easiest first.....

Water level.....
then
Thermostat froze open or shut or half way.
Froze thermostat of any kind can prevent heater from working.

Likely one of those two.

 

Wouldn't this be a stuck door, bad controller, or a vacuum issue? If both hoses are hot, the core is getting hot water and there's probably plenty of coolant and the thermostat is probably not stuck open.

 

I think it could be the blend door on the HVAC.

 

I would think if it's the door he would still get heat, it just take longer to warm. You should be able to hear the door open and close when you cycle the selector switch from max a/c to any thing else.

 

First thing I checked was coolant, full. 2nd was hoses, both hot. 3rd was to listen for the door to open/close when I try to adjust temp. I hear nothing. Where to look at the door is what I am trying to do now. Could be a vac issue and the door is not able to close. Any ideas on how to check the door issue?

 

No heat is ussually a circulation problem.
Slow to put out heat or low heat, might be a blend door.

Just because the hoses are hot to the touch, just means that there is some flow, may not be sufficient flow.
Causes can be:
Vapor locked (Air bubble)
1/2 open thermostat
Plugged water passage (including heater core could be plugged)
Weak Water Pump

With the exception of replacing the water pump or heater core, the rest take less than 15 mins "first time doing it", and less than $10.
If it's plugged water passage, including plugged heater core then you may be able to use a radiator flush to open it up with out havening to remove it, or a radiator shop may be able to use their industrial flush and not have to remove it. If you find you have to replace the heater core, then I'd probably pay a shop to do it. Weak Water pump, I'd change prbobaly do that myself.


With heater on, using infrared thermometer, there should be at least 40% drop in temp between the two hoses at the fire wall. (IE in to core hose = 100º, then out should be atleast 60º). Any less than 40% difference indicates no air flow across the core. Fins are plugged with debris or dirt or blend door is closed.
Anymore than probably 60%, (in = 100º, Out=40º or less) likely indicates insufficient coolant flow. Because they just aren't "that" efficient.

Blend door can be:
Selector switch (control panel)
Vacuum leak
Bad Vacuum servo
Linkage froze or broke
Blend door froze

Plan on a couple of hours to get to most, and if your like me, tearing up some stuff along the way. Cost can vary from a couple of bucks for vacuum line and fittings (plus what ever you tear up along the way) to new control panel probably being the most expensive. With the exception of the control panel, I'd change the control panel myself. The rest of that I'd likely take to a shop and pay to have done. I might be inclined to investigate a vacuum leak, as I have all the gauges and test tools here. But if I couldn't locate it after an hour or so, then it'd go to a shop because I'd be pissed. I don't have the patience for it that I use to.

 

Also check to make sure that the hot/cold air **** on the dash is installed properly and not stripped out. You could be turning the ****, but not turning the shaft the **** sits on. If the plastic **** is stripped out some, you might be able to get it to 'bite' by pushing on it as you turn if from cold to hot.

The **** should pull right off. Before you do any major surgery, I would take the **** off, inspect, and reinstall, making sure it is lined up right. Then push hard on it as you turn from cold to hot.

Good luck!

 

The only time you hear the blend door is selecting between A/C > panel > Off > floor > floor/defrost > defrost

Moving the temp control you won't hear anything.

 

Excellent point.

That would be an easy temp fix! If thats it then use pliers to turn it to hot until weather/time/money to find a new ****. Might have to buy the entire control panel just to get the ****.... I'd check salvage yards, if thats it.

 

As I turn the controls from AC through heat, defrost, I hear nothing. It will blow (fan works) not freezing cold air, but just cold air. (like the door is stuck open) How do I get to the door to "see" if it is open or closed?

 

Not quite... The blend door controls whether you're getting hot air in or cold air in. When mine went bad, you'd hit the brakes and it'd go to hot. If you gassed it, it'd go to cold.

TDF, best way to see if your blend door is working is to try and change the temperature. I know, its hard right now with it being 28* and snowing, but, you still should be able to notice some change in temperature if it is working.

 

Where is the blend door? Unter the dash or engine area?

 

This might be a quick fix.....

Not my grandpa, Grandpa i a member on here.....


So you can use a wire to check the blend door (I had never thought of that) and check your fuses..... I did not know that it was electric... I learned something!

That is why you won't hear it.