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Where does the ac vacuum line come out if the firewall in a 99 expedition

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Posted on Jan 02, 2017

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dcramer531
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SOURCE: 2001 Chevy 1/2 express van.A vacuum line under

The vacuum line from the engine's intake manifold goes to a vacuum reservoir ball under the hood; from there a vacuum line leaves this reservoir, passes through the firewall and connects to the mode control switch.
The mode switch directs vacuum to actuators that position the doors to the desired vents. When there is no vacuum the doors are pulled by springs to a rest position; defaulting back to defrost.

The vacuum reservoir is used to store vacuum when the engine is under load and not producing large amounts of vacuum. The inlet vacuum line may have a check valve; stopping vacuum from going back to the engine. Make sure that this valve (if there) will only allow vacuum to pass through it in one direction.

The lines that control the AC and heater all pass through the firewall and some are up around where the wipers are if there are no lines coming out of the firewall except the one by the brake booster then simply plug the line coming off the T with a screw and see if that restores your vacuum to the controls. You may just be leaking so much your controls arent working. These lines that run around the manifold tend to disenegrate over time and with out seeing the issue I have to guess that the one unconnected line is either broken off and should connect to something withing its length or the hose itself could be cracked in half which leaves the other half hanging out there somewhere.
You might need to remove the center console & the engine cover in order to access the main vaccum line that is right in front of the PCV valve on the driver's side of the engine. Make sure you have a really long flat head screw driver to remove the two slotted bolts on the engine cover on the firewall. Also, since the placement of the vacuum hose is definitely a design flaw as it cannot stand up to the heat of the engine for more than a few years without degrading the line, make sure you invest in a heat shield wrap or another larger vacuum hose to engulf the replacement hose & to act as a heat shield. I recommend replacing all of your AC vacuum hoses at the same time

Posted on Jul 29, 2011

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1 Answer

When I stepping my gas for 2003 ford expedition AC blowing no air, what's the cause of that?


AC blend air doors operate off of engine vacuum and when you press the gas pedal vacuum decreases. The vacuum lines for AC control have a check valve (under the hood along the firewall) and a vacuum reservoir which are supposed to keep vacuum on the system when engine vacuum is low. Check that all lines are good with no leaks and that check valve is working. Even a small vacuum leak can cause this issue.

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Blend door works properly only thing i cant find is a control valve in is climet control i thought maybe ac staying on no that not it i out of ideas i need help


FOLLOW 2 hoses that go thru the firewall ..the heater control valve should be near the heater core...2 vacuum lines attached too

Jan 24, 2011 | 1998 Ford Expedition

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AC is blowing cold air, but it is coming out of the defrost and not the front vents. Why are the front vents not working?


Check over on the passenger side under the hood by the fire wall, there will be some elec. connection, just below that there will be a small vacum line that should go into your fire wall, check that it has vacum, it should also have a one way valve, small round looking some time that get clog, needs to have vacum that is what power the blend door's.

Jun 30, 2010 | 2003 Ford Expedition

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Where do i add freon on 2003 ford expedition


Find the ac compressor under the hood,and look at the ac lines coming from it,there is a large one,this is your low side ac line,follow it toward the firewall,and you will come to it.If this was helpful,please rate,thank you.most of them are on the passengers side near the fender near the firewall.

Jun 27, 2010 | 2003 Ford Expedition

1 Answer

97 ford expedition. AC blowes out the defrost not panel. knob will turn off but air will only blow out defrost


The air control doors on your vehicle are vacuum operated and shift by themselves to a "default" position [which is defrost] if the vacuum is lost. I would suspect that you have a broken or leaky vacuum supply line near the engine somewhere which is preventing vacuum from ever reaching the control panel. Look for a broken or leaking small 1/8" or so diameter black plastic vacuum line near the rear of the intake manifold area on the engine. This line may go to a plastic vacuum reservoir or it might just go right to the firewall and pass through it with a group of other items [it varies from model to model] If you can't find it you might need to have someone at a service facility track it down for you. Should be a fairly simple fix. Good luck, hope this helps a bit!

Jun 25, 2010 | 1997 Ford Expedition

1 Answer

I have a expedition 03 my ac isnt shooting through my vents its shooting upward to the front windshield n not directly at the driver or passenger


The mode doors are vacuum controlled. This vacuum is produced by the intake on the engine. When you lose vacuum to the dash for the vacuum actuators which move the doors. It defaults to defrost. So most likely you have a leak inside the dash or on the engine side of the firewall prior to the vacuum even entering the cab

Mar 01, 2010 | 2003 Ford Expedition

1 Answer

I HAVE A 97 FORD EXPEDITION THAT STUCK IN 4 WHEEL DRIVE


Possible solution..Expedition uses a vacuum solenoid on the firewall that controls vacuum to the 4-wheel drive actuator. Vacuum "unlocks" the 4-wheel drive, so you may have a leak in the line to the actuator so the 4-wheel drive is always on. Seems backwards, I know.

Dec 07, 2009 | 1997 Ford Expedition

5 Answers

Where does the freon go for a 99 expedition


Hi .. I just ran into the same problem .. I have a 2000 Expedition with the 5.4L engine .. the low side port is located on the passenger side of engine compartment just below the black metal bracket that contains electrical connections right in front of the firewall... you have to reach under this and locate the low side (larger line) and feel for the connection .. it is right in front of the accumulator .. There are two heater hose that hide the port .. you have reach under these to unscrew the port cap which is black .. you'll have to do this by feel .. I have found that you can by R134A charge with dye and leak sealant helps with small leaks .. if the system takes more than two cans be usre to add refrig. oil .. hope this helps

Jul 19, 2009 | 1999 Ford Expedition

1 Answer

Air conditioning and heating problem


The blend door actuator is vacuum driven. It sounds like you have a vacuum leak. Trace the vacuum lines starting at the firewall in front of the passenger side. With the heater or AC on HIGH and directed at the front vents, listen for a leak or trace the vacuum line back ward to try to find a leak. All the best.
Greg

Jun 22, 2009 | 1999 Ford Ranger SuperCab

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