Mountaineer heater issue, ac compressor come on with the heater.

[Rick. VL]

My 2000 Mountaineer V8 has developed a heat issue. It blows cold, but the ac compressor kicks on while in heater mode, not just in defrost mode. I recently replaced the intake manifold gaskets and in the process, snapped of the heater control valve. I replaced it, and now I have this issue. Is it possible the new valve is bad, and could the thermostat be bad? Fluid levels are good, gauges are normal. Thanks for any advice on this.

 

[MakinJeepsWeep!]

The a/c should run with the heater on strictly for humidity, should just cycle here and there, but on those control valves they are directional, most have a arrow on them. Is it in there the right way?

 

[MakinJeepsWeep!]

I just did this on my 06 Mounty

 

[1998Exp]

I just did this on my 06 Mounty

I replaced that valve some time ago. The new one was confusing, because when installed properly, the vacuum port is awkwardly facing the wrong way. Nevertheless, I am holding the old one as I am writing this -- even if the arrow is pointing the wrong way, it allows flow when open. Seems that the arrow is there to prevent the pressure from forcing it open when it's commanded to close.
My guess is that the O/P has a different problem - perhaps an obstruction in the heater core or a defective blend door (or its actuator). The easiest way to check would be to bypass the valve - the hose should be long enough to simply hook it directly to the heater core.

 

[MakinJeepsWeep!]

True, I did not see a real reason it would not operate either way and i agree the right way looks wrong, but it was on there for a reason whatever it may be. You/he could always just manually move the lever instead of unhooking things to see.

 

[1991 sploder]

I have the same problem 2002 crown vic it's a head scratcher I'm replacing the heater core (again) but any time anything air is on the ac clicks on I feel like the vacuum line has a leak. Frustrating seems electronic/vacuum combo.

 

[MakinJeepsWeep!]

The air conditioner compressor is going to come on when either you turn on the hot or the cold air, its the only thing that drys the air, if not you would never de fog your windows but instead you would end up with a sauna in your cab, its air conditioner compressor not cold air compressor.

 

[Rick. VL]

The a/c should run with the heater on strictly for humidity, should just cycle here and there, but on those control valves they are directional, most have a arrow on them. Is it in there the right way?

Ok, I checked it out, it appears to be installed the right way. Didn’t see an arrow on it. I put it in the same way I took the old one out. The vacuum line is on the front side toward the front of the car.

 

[MakinJeepsWeep!]

Okay, so we know it worked before right? broke the end off it was replaced correctly now it does not work. Antifreeze is full i assume. You can try moving the valve by hand and see if you get hot air. You can also try having someone else move it from hot to cold in the cab to see if the valve is working, if the valve moves when it is changed we know that works and or if you move it by hand and there is still no hot air the only options you have is your heater core just happend to get clogged when you did the work or you just so happen to have a broke blend door at the same time. because if it does not over heat we know the thermostate and the water pump are working, you move the valve by hand we know heater core is being supplied hot antifreeze, so after that all you have left is door or clog. There isnt anymore to the system. I hope this helps im curious!

 

[CDW6212R]

FYI, the air compressor runs in all positions except for VENT and OFF.

 

[Rick. VL]

Okay, so we know it worked before right? broke the end off it was replaced correctly now it does not work. Antifreeze is full i assume. You can try moving the valve by hand and see if you get hot air. You can also try having someone else move it from hot to cold in the cab to see if the valve is working, if the valve moves when it is changed we know that works and or if you move it by hand and there is still no hot air the only options you have is your heater core just happend to get clogged when you did the work or you just so happen to have a broke blend door at the same time. because if it does not over heat we know the thermostate and the water pump are working, you move the valve by hand we know heater core is being supplied hot antifreeze, so after that all you have left is door or clog. There isnt anymore to the system. I hope this helps im curious!

Thanks. I will try all those things tomorrow and let you know how it goes.

 

[MakinJeepsWeep!]

FYI, the air compressor runs in all positions except for VENT and OFF.

Correct.

Good deal Rick let us know what happens!

 

[C420sailor]

And in the manual control vehicles, A/C compressor is commanded for all modes except OFF, panel only, and floor only. So in either defrost mode, either AC mode (obvi), or panel AND floor mode, AC will engage regardless of hot/cold mixer setting.

 

[MakinJeepsWeep!]

In my 96 x 5.0-06 merc mounty 4.0-01 Mazda b 3.0-the all are the same as far as the ac on command. The 96 and 01 are the same but merc is dual climate with fancy buttons and such and rear climate control as well. The reason is simple here in south Texas where I am it is so hot and humid or cold and wet you need both to pull moisture out of the air and make it the temp to your liking. The way the air boxes are made your air comes through your condesor coils first then through your heater core if on and the out of the vents.

 

[MakinJeepsWeep!]

To the best of my knowledge on how that works anyway. Seems that's how it works

 

[CDW6212R]

Ford has operated the AC systems this way for decades. The compressor is commanded to run 100% of the time except when the AC control is OFF, or VENT. It runs in all other positions.

 

[MakinJeepsWeep!]

Yuppers and it makes sense. Takes the humidity out.