hvac question
 

Just picked up a 2000 ext cab Dakota with the v-6

Here is my question

If I turn the heat on I can can hear it blowing but it wont come out of any of the vents. The hoses are hot and temp gauge is ok, but if I turn it to the a/c it blows out of every vent when chosen.


So If I want the a/c on the floor it works fine, on defrost works fine etc.

It will not do that for the heat though.

Any ideas?

Thanks

I'm sure I will be asking a lot of questions as I got this truck for a steal and it was used as a camp truck to tow a boat in the summer and during hunting season, so it sat in the barn a lot.

Thanks

Rich

If you can get it to come out of all the locations, at some point, the actuators themselves are OK.

It sounds like a control head issue. Basically, all you are doing when you select a function is applying a vacuum or venting. The control head is basically a multi-position valve.

Try a boneyard.

Do you have a link as to what i would be looking for?

I am fine with doing the repairs myself but dont know what I would be looking at or for?

There isn't much to the system. You have the panel vents, the defroster vents, the floor vents and a recirc door that are controlled by vacuum. The control head is what directs the vacuum or vents it as required.

If all the actuators are working - which you indicate in your first post that you can get air to blow from them all, just not in some positions, then the only likely source of the problem is the control head - the HVAC controls.

You can verify the actuators are functioning using the attached diagram.

Is this actuator behind the glove box? Could I bypass it, so the heat works and not the a/c until I get the part?

They're behind the dash and pretty much impossible to reach without rolling it back.

You SHOULD be getting some heat, even if out of the wrong vent. The "blend door" that controls how hot the air is, is cable operated.

So, just to make sure I understand you correctly is the problem - no heat at all OR is is that the air doesn't come out of the right vents?

Thanks for your help

I have a update and a answer to your question.

When you select any setting on the vents - upper, floor, defrost - they work fine with the temp control set on cold. Move the temp control towards heat and the airflow gets completely restricted in any setting. Move the temp back to cold and the air comes blowing out.

So something is switching it from cold to hot but the hot air wont come out , is there a vacuum line or is there a rod/wire that does it?


I was out there looking around and against the firewall there is a vacuum line that goes across the whole length of the firewall. One end tot he brake booster and then there is a tee and the end goes into the firewall near the heater hoses. The end of the tee, that line is broke and has a screw in it but the line that i think it attaches to goes down to the right side of the fender to a round metal thin that I am assuming is vacuum related.

So could this broken vacuum line be causing this issue?

There are no actuators under the hood. They are all mounted on the HVAC core.

They are actuated by vacuum, except for the blend door. It is cable operated.

It sounds like you may have something blocking the heater core. Not the flow of coolant, but air over it. It could be leaves or other debris.

The vacuum line you are tracing feeds the heater control head and then leads to a reservoir (plastic tank) under the cowl. It also supplies the cruise control servo.

It does not sound like a vacuum issue - at all. It sounds like a blend door/obstructed heater core issue.

I think you'll find yourself pulling the dash.

I think I might have something behind the dash, as the truck was sitting in a barn as it was only used here and there.

There is a awful smell like cat/mouse pee, so i agree that There is something in there. I smacked the dash a few times and some hay or something like it fell out.

Now I "rigged" a line to attach the line I refereed to on the fire wall and now it will only go to defrost when I have the cold selected, before it was coming out of all vent's.

I'm going to take it to my wife's work on Friday and use there garage.

I'm replacing the radio at the same time, think I will be able to just pull back the passenger side of the dash and see if there is "stuff" in there?

The HVAC system defaults to defrost when there is no vacuum supply to the control head.

You can't pull really pull back one side of the dash, it's all one piece. You can't access anything without rolling the dash back and taking the HVAC core out. You need to drain the coolant and evacuate the a/c to do that.

If you're going that far, change the core out.