I have a 2005 F450 6.0. The truck has a vacuum actuated shut off valve on the hose at the heater core. The valve is opening in the heating or the max cooling mode. If I remove the vacuum line the valve closes and the ac cools very well. How do I go about trouble shooting the vacuum control? Thanks for your help.

 

I don't really understand the question, but I'll give you a free bump and some worthless advice.

It sound's like there is constant vacuum running when there shouldn't be? You can pull a line off the vacuum pump and put your finger over it. If it shuts itself off after a few seconds then its working properly. I never messed with the 6.0's AC much so I don't know how all that shenanigans goes together without looking at it.

 

The heater control valve is a normally open valve. When you apply vacuum to it it is actually closing the valve shutting off flow through the heater core. On vehicles with manual climate control when Max A/C is selected vacuum is applied to the valve closing it and shutting off flow through the heater core. I can't tell you why in your case the A/C appears to be working better with the valve in fact open.

 

Is the door motor (to let air go past heater) normally closed so it normally have "no heat"?

That way, when you detach the vacuum line, the door is closed, and AC cold because it is no longer being passed through the heater.

However, if you connect the heater valve vacuum line to the coolant shut off valve, if that valve is defective, it just lets in air and do not shut the coolant flow while the heater door is simultaneously in the "open" position and now blowing air through the heater core with coolant not cut off / still circulating?


If I am right, you have a bad heater coolant shut off valve that is either only partially or not shutting off coolant at all.

These valves are prone to corrosion and failure.


I am assuming you measured the vacuum with a gauge and there is sufficient vacuum.

 

What I found was the temperature of the ac was was getting warmer the longer the truck ran. I suspected the heater shut off valve was not closed.

I removed the valve to verify its closed position. This valve is closed until vacuum is applied. When I start the truck and turn on the heat the valve opens and hot water is circulated through the heater core. But when I switch over to AC the valve is not closing, allowing the hot water to continue to circulate through the heater core. I am measuring a 7+deg. increase at idle as the truck warms up.

The rest of the system seems to be operating fine. The system will blow air through the defrost, panel and floor vents when called for. The recirculation door closes also.

What I am trying to determine is there a way or is the system designed to shut off the vacuum signal when not in heating. I could always install a solenoid valve and control it manually. But I suspect there is a way for the climate control to turn it off?

 

Do you have the electronic controls(EATC) or manual dials?

 

I have the electronic controls, the truck is the Lariat model.

 

This is a little confusing one I can only assume he is refering to the valve in the engine compartment on the heater core hose. Ford refers to this valve as the Heater control valve. The valve is a normally open valve so with no vacuum present at the port, unplugging the vacuum line when vacuum is present, or if the diaphram was bad would render the valve in a open state. He states that in Max A/C he removes the vacuum line and the valve mechanical changes posistion which tells me the valve was in the intended closed state which is normal for Mac A/C. But thats as far as I can go I have no experience with the cabin vacuum servo's under the dash and there proper operation. Going out to the Inlaws today for mothers day and the father in law has a 2003 XLT but as I seem to remember reading that year may not have the Heater control valve. I have a Lariat with automatic climate control with no way to get to max A/C manually so I can't check this senerio. Just thinking he may be looking at the wrong valve for the sorce of his proplem.

 

Thanks for all of the responses.
I hope I can clear up some of the confusion. The heater control valve in my truck is in the closed position with out vacuum. I confirmed this with the valve removed from the truck. When vacuum is applied the valve switches to the open position allowing hot water to flow through the heater core.

 

There are a few things you can check. Look behind the glovebox and you should see a set of colored vacuum lines. Make sure all the connections are tight.

There is also an electro mechanical manifold that takes electrical input from the EATC and does the switching/distribution of the vacuum system to the zone selector door/recirc door, etc. This should be located on the firewall behind the EATC. You can find it by tracing the vac lines behind the glovebox. Look for loose connections/ listen for leaks.

Lastly is the EATC head unit itself. You can perform a simple self diagnostic routine on the head unit. Just to add to the text in the link, press and release "Auto" and floor zone control, then quickly hit "Auto" to start the routine.

I had a problem with weird stuff happening with mine years ago. There are other diagnostic procedures in the service manual for the manifold and EATC outputs. They are an absolute PITA to perform. I did the self diagnostic and no codes came up. Took it to the dealer and they installed a new head unit and all is well. They didn't go through all the troubleshooting, they just swapped the HU to see if that was the problem, and it was. Hopefully you find a line disconnected or leaking.

 

IIRC, You can toggle between Max A/C with the cabin recirc button.

 

Interesting I have a 2005 F350 Lariat with Automatic climate control and the heater control valve on it is normally open and closes with vacuum applied confirmed that a month ago when I put my coolant filter on and just reconfirmed it a few minutes ago at the cost of a cup of antifreeze in the driveway just to make sure I wasn't crazy. Mine is a early build 11/04 2005 so maybe thats the difference. Guess it just goes to show you it hard to work on someone else's problems over the Internet. Remember reading a TB somewhere on the 05's about the vacuum connections behind the glove box but can't find it now.

 

He it is. Know you don't have the major leak but it may be a spot to inspect.


2005/06 A/C or Ventilation Control Problems:
Trucks built between 9-15-04 to 6-8-05 may blow air out of the defrost vents with the mode selector in other positions. The vacuum pump may also run excessivly. Lower the glove box and inspect the vacuum lines to see if they are wraped around the panel/floor door actuator rod. If the hoses are wraped around the rod, inspect for damage to the hoses. If the hoses cannot be repaired, replace them with part number 5C3Z-19D699-AA for automatic temp control or 5C3Z-19D699-BA for manual climate control.
TSB 05-14-9.

 

Just to update I ran the diagnostics as suggested by William_o4_x, thanks. There were not any codes. An interesting development since yesterday. At first the hot water valve would not close (vacuum always present), today there is no vacuum at the valve. The valve is not opening in the heat or AC mode.
Located the electro mechanical manifold control unit and verified all wires and vacuum tubes were connected properly. And checked the vacuum line connections behind the glove box those were all connected I suspect the electro mechanical manifold is faulty, first the valve stayed open and today it is staying closed.
Tomorrow I'll try and replace it and let you know how it turns out. Thanks for you suggestions.

 

Hey, if you think you might have a electronic glitch... do master reset as per link below...

I have cured more problems with that than giving aspirin to FTE forum people.