HVAC

D

Dougt

Registered
Hi, I have a 94 Mark VIII and it was parked for a couple of months. When I started it up, the A/c wouldn't work. The compressor kicks in for a couple seconds then out again. To make it worse, only heat comes out of the vents. I don't know if it is related, but the outside temperature is reading -40 no matter how hot it is outside.
Oh, I had the guages put on the A/C and there seems to be lots of freon. Any suggestions? Doug
 
RE: HVAC

Welcome!

Perform a EATC diagnostic test first...

On-Board Diagnostic

NOTE:
The in-vehicle temperature should be greater than 10°C (50°F) for all DTCs shown to be valid.

l The control assembly will detect electrical concerns occurring during the On-Board Diagnostic.

l Ensure that the engine is warm, at least 120°F coolant temperature.

l To display the DTCs, initiate the On-Board Diagnostic by pushing OFF and FLOOR simultaneously and then AUTOMATIC within two seconds. The test may run as long as 30 seconds, during which time the display will be blank. If the display is blank for more than 30 seconds, go to System Diagnosis When On-Board Diagnostic Indicates No Errors Found.

l The On-Board Diagnostic Test can be initiated at any time with the resulting DTCs being displayed. Normal operation of the system stops when On-Board Diagnostic is activated. To exit the On-Board Diagnostic and restart the system, push the BLUE button. The On-Board Diagnostic should be deactivated before powering the system down.

Condition(s):
o EATC System Concern

o 01 (Code Displayed During Diagnostic Procedures)

Possible Source(s):
§ Damaged control assembly.

Action(s) to Take:
§ Replace EATC control assembly.

o 02 (Code Displayed During Diagnostic Procedures)

Possible Source(s):
§ A/C air temperature control door damaged or inoperative.

Action(s) to Take:
§ Refer to «A/C Electronic Door Actuator Motor Diagnosis» .

o 03 (Code Displayed During Diagnostic Procedures)

Possible Source(s):
§ Automatic temperature control sensor open or short.

Action(s) to Take:
§ Refer to «Automatic Temperature Control Sensor» Diagnosis.

o 04 (Code Displayed During Diagnosis Procedures)

Possible Source(s):
§ A/C ambient air temperature sensor and bracket open or short.

Action(s) to Take:
§ Refer to «A/C Ambient Air Temperature Sensor» Diagnosis.

o 05 (Code Displayed During Diagnosis Procedures)

Possible Source(s):
§ A/C sunload sensor short.

Action(s) to Take:
§ Refer to «A/C Sunload Sensor» Diagnosis.

o 888 (Code Displayed During Diagnosis Procedures)

Possible Source(s):
§ Temperature control lockout valve and switch inoperative.
§ Vacuum system inoperative.
§ A/C clutch inoperative or damaged.

Action(s) to Take:
§ Refer to «EATC System Functional» Test.
 
RE: HVAC

-40 is the default reading the EATC displays when there's an open circuit to the ambient air temperature sensor. It may be unplugged, damaged, or there's a wiring problem.

If the EATC system is led to believe that's how cold it is, there's obviously no need to run the compressor!

The sensor is forward of the rad, near the hood latch. It has a pointed end and threads like it should be screwed into something, but is clipped to the rad cradle. Look for a two wire connector with red/orange and pink/black wires going into it. When you find it, jump the pins, turn the key on, and if the wiring is good, the display will jump to a crazy high reading. If I remember correctly, I believe the short circuit default is 130 deg.

Usually, when the compressor cycles quickly, it's an indication of low refrigerant, but you say it's OK.

You won't be able to properly diagnose the system further until the control portion of the EATC can correctly read ambient temperatures. Fix that first.
 
RE: HVAC

[div class="dcquote"][strong]Quote[/strong]
-40 is the default reading the EATC displays when there's an open circuit to the ambient air temperature sensor. It may be unplugged, damaged, or there's a wiring problem.If the EATC system is led to believe that's how cold it is, there's obviously no need to run the compressor!The sensor is forward of the rad, near the hood latch. It has a pointed end and threads like it should be screwed into something, but is clipped to the rad cradle. Look for a two wire connector with red/orange and pink/black wires going into it. When you find it, jump the pins, turn the key on, and if the wiring is good, the display will jump to a crazy high reading. If I remember correctly, I believe the short circuit default is 130 deg.Usually, when the compressor cycles quickly, it's an indication of low refrigerant, but you say it's OK.You won't be able to properly diagnose the system further until the control portion of the EATC can correctly read ambient temperatures. Fix that first.
[/div]

Good stuff here. I've had this issue on both my Marks before. Found out that the connector wiring was bad.
 
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