Vacuum

Tiny
PC561
  • MEMBER
  • 1998 LINCOLN NAVIGATOR
  • V8
  • 2WD
  • AUTOMATIC
  • 50,000 MILES
1998 lincoln navigator turn on ac it gets cold within seconds you can hear a door shut or slam and the air starts blowing warm to hot. I know it has something to do with the vacuum but how do I find it or trace it out
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Thursday, June 30th, 2011 AT 10:15 PM

8 Replies

Tiny
WRENCHTECH
  • EXPERT
No, it's not vacuum. The temperature is controlled by the use of an air mix door that is operated by an electric motor/actuator. This door can be jammed or the actuator can be inoperative or have stripped plastic gears internally.
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Thursday, June 30th, 2011 AT 10:35 PM
Tiny
PC561
  • MEMBER
I can hear the door close, there for I know it's not jammed. All other vents work fine. They open and close this just happens when I turn on the airconditioning. Where is this door, and is this motor fused
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Thursday, June 30th, 2011 AT 10:42 PM
Tiny
PC561
  • MEMBER
Excuse me but you mentioned an actuator where is this and what does it do, how do I find it and see if it is working or not.
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Thursday, June 30th, 2011 AT 10:47 PM
Tiny
WRENCHTECH
  • EXPERT
The actuator is the motor that operates the door. It is powered by the main A/C controls.

It's mounted on the lower side of the HVAC housing which is very difficult to access.

Description and Operation

The A/C electric blend door actuator is located on the plenum assembly.

* Its function is to move the air temperature blend door on command from the control assembly.
* The A/C electric blend door actuator contains a reversible electric motor and a potentiometer. The potentiometer wiper is connected to the actuator output shaft and moves with the output shaft to indicate the position of the air temperature blend door.
* A 5 volt signal is applied to the ends of the potentiometer. The voltage available at the wiper indicates the position of the potentiometer. The expressed value of the actuator wiper voltage is sent to the Electronic Automatic Temperature Control (EATC ) module and is compared to the desired wiper voltage determined by the EATC module. The control module then drives the actuator motor in whichever direction is necessary to make the actuator wiper voltage agree with the desired wiper voltage.
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Thursday, June 30th, 2011 AT 10:53 PM
Tiny
PC561
  • MEMBER
Wow O.K. Is it possible to disable this actuator so that I have just airconditioning.
You say it is hard to access, I'm guessing it is behind the passenger air bag.
I'm serious would there be any harm in disableing this motor?
Also can it be done say temporarily so just the AC works?
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Thursday, June 30th, 2011 AT 11:14 PM
Tiny
WRENCHTECH
  • EXPERT
Sure, it's possible to remove the motor and position the door manually but that would be pretty foolish and impractical. The issue here is getting access to it. The part is only about $100 if the actuator itself is bad. It's what it takes to get to it. It's in the general area of ahead of the console.
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Thursday, June 30th, 2011 AT 11:19 PM
Tiny
PC561
  • MEMBER
O.K.
If I could get access to it I wouldn't disable it I would replace or fix it, if I have to go through that much trouble.
I was talking about say pull the fuse for the motor, or temporarily cut the hot wire to it, cause when the car is turned off the door goes back.
Then there is also the part where lets make sure that this is the part that is bad. How do I go about trouble shooting it to make sure before I start such a tedious job?
If you have time to answer, you have been very helpfull so far.
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Thursday, June 30th, 2011 AT 11:57 PM
Tiny
WRENCHTECH
  • EXPERT
I'm afraid this is the end of the line for me. You need an electrical technician to troubleshoot the problem on site.
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Friday, July 1st, 2011 AT 12:05 AM

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