HVAC question

94_Linc_mk8

94_Linc_mk8

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What up. The climate control works great in my '94 mark viii, all the temps work, and all the positions, but nothing comes out of the panel vents. No heat or A/C, but just out of the panel, the floor and defrost work fine all the time.
 
from what it sounds like it might be your what is it called door blend or heater core
 
one other thing i can think of is a leak some where
 
94_Linc_mk8 said:
What up. The climate control works great in my '94 mark viii, all the temps work, and all the positions, but nothing comes out of the panel vents. No heat or A/C, but just out of the panel, the floor and defrost work fine all the time.
Click to expand...

I was trying to say that my system works great, it just doesn't blow out of the panel, thats the only problem with it. Could it be the intermittent blower motor, or maybe the blend door, if so, are there any fixes?
 
Most likely a vacuum issue. See if these help...

eatc%20vac.jpg


Electronic Automatic Temperature Control (EATC)


How The Circuit Works


The EATC System automatically maintains a selected temperature for individual driving comfort by regulating the discharge air temperature when set in any position except OFF. The fan speed, when set to AUTOMATIC, is automatically regulated as determined by the vehicle interior temperature. The selected temperature settings are 60 °F (maximum cooling) to 90 °F (maximum heating).

A provision is also available to manually override the auto blower function with the blower potentiometer. Moving the Potentiometer provides a continuous variable blower speed range from LO to HI. The blower operates in all function positions except OFF.

Automatic
Pushing any button, except OFF, will put the system in automatic operation. The WARM and COOL buttons allow the user to change the set temperature. The A/C compressor is automatically engaged in all function positions except OFF, VENT and FLOOR. The discharge air temperature and blower speed are automatically set to quickly bring the vehicle interior to the set temperature. Setting the temperature higher or lower than the comfort setting will not heat or cool the vehicle faster than when set at the desired temperature. During cold weather, the fan will not operate in the FLOOR position until the engine reaches a predetermined temperature.

The air conditioner and heater are controlled automatically to achieve the selected in-car air temperature. To maintain comfort, the instrument panel registers can be tilted up or down and side to side. The registers can also be closed.

Blower Speed Override
Moving the selector lever to LO fixes the blower speed in low. Moving the blower temperature lever between LO and HI will allow a speed proportional to the position of the potentiometer and cancel the auto blower control. The system will continue to maintain the set temperature during blower override operation.

Air Discharge Locations
OFF-Pushing OFF button stops all systems operations.

MAX A/C-Pushing MAX A/C button provides cooling with recirculated air through the instrument panel outlets. The compressor will operate.

VENT- Pushing VENT button provides outside air flow through the instrument panel outlets. The air can be heated but not cooled in the vent position. The compressor does not operate.

PNL-FLR-Pushing the PNL-FLR button allows outside air to be discharged from both instrument panel outlets and the floor outlets. The compressor operates to dehumidify the air.

FLOOR- Pushing FLOOR button allows outside air to be discharged through the floor outlets. The air can be heated but not cooled in this position. The compressor does not operate.

FLR-DEF-Pushing the FLR-DEF button directs outside air out the defroster outlets and the instrument panel outlets. The compressor operates to dehumidify the air.

DEFROST-Pushing DEFROST button directs outside air out the defroster outlets against the windshield. The compressor operates to dehumidify the air.
 
dam you beat me too it i w as thinking that last nite i had a issue like his a leak somewhere
 
You can see from the schematic, the panel vacuum motor has vacuum applied to it in the Max AC, Vent and Panel/Floor positions of the EATC. This means the vacuum motor is supplied vacuum to operate a door to divert air flow to the panel vents. In a lack of vacuum, the motor is spring loaded to close the door and block air from the panel vents.

This is where I would start. Find the yellow vacuum line from the rear of the EATC. Follow it to the vacuum motor. Check for vacuum in the yellow line at the vacuum motor connection. If you have vacuum available in the appropriate EATC functions to the vacuum motor, the motor is jammed, linkage is broken or diaphram is ruptured. If no vacuum is present in the yellow line at the vacuum motor, you have a blocked line, broken line or faulty EATC(assuming other vacuum functions work).
 
I finally got around to removing the EATC and the vacuum lines look good. My question is, where is the vacuum motor supposed to be, thats the next place im going to look.
 
How often is the unit itself bad, because I can feel the very, very, faintest amount of air coming out of the panel vents. Could the EATC be bad on certain settings, or is that to uncommon.
 
I had the same problem you did, my problem was that the yellow vacuum line got disconnected from this...
Panel_DefrostVacuumMotor.jpg


This motor can be found by looking up under the dash, driver's side, towards the center console... You have to get in an akward position to see it, but it's silver and somewhat easy to spot... Even if the hose is attached it may not be on enough, so make it tight and snug...

Note: The only reason the yellow line in my situation was pulled out is due to me changing out the EATC to the newer button style unit...

Good Luck
 
Try this before you get into the dash.
My Mark blew cold and hot air but just out of the defrost and floor. There is a check valve behind the passenger side wheel house next to the firewall. A line runs from it to the intake (red colored). Unplug that line from thje check valve and check for vacuum. If not replace that line. If so unplug the other two lines from the check valve, one runs to the canister and the other goes into the firewall and connects to the EATC. Connect the first line up to the EATC line and see if the A/C works correctly. If it does then the line to or the canister itself in the wheel well is bad.

It could also be that the vacuum plug on the back of the EATC is loose or off. If there is no vacuum to the EATC then it defaults to defrost.

Hope this helps.
 
It was a combination of all three, vacuum to the EATC, vacuum to the check valve, and vacuum to the vacuum motor, but I got it all fixed, and it works great! You guys saved my life, becase it's like 101 outside. Thanks alot.
 
94_Linc_mk8 said:
It was a combination of all three, vacuum to the EATC, vacuum to the check valve, and vacuum to the vacuum motor, but I got it all fixed, and it works great! You guys saved my life, becase it's like 101 outside. Thanks alot.
Click to expand...

Cool!:wrench:wrenchGlad to be of help!
 
fixed my problem too - the vacuum line at the intake was off. thanks a lot guys, you saved me a lot of headaches.
 
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