[MattN]

I've read quite a few of the A/C threads here, and am not entirely sure that I was able to find exactly what I am looking for - and I admit to not knowing a lot about automotive A/C. So please bear with me, thanks.

I have a '97 T-Bird with the 4.6L V-8. The A/C isn't putting out cold air, but here is some information that I hope can be used to point me in the right direction:

The compressor is turning, and the clutch is engaging/disengaging. It seems to spend 2-3 seconds cycling, and 7-8 seconds not cycling.

AFAIK, every selector switch for redirecting air - be it out the dash vents, the floor, the windshield, etc. seems to work fine.

The engine RPMs go up and down (which I believe is normal) when the A/C is cycling and not cycling.

I can definitely get hot air by increasing the temperature.

With the A/C on for a few minutes, one of the lines in the engine compartment does get *very* cold to the touch and even has condensation on it, which tells me that R-134 is in the system and flowing- I think, if you are looking at the firewall when standing in front of the car with the hood up, it's the right-side line. However, I do not see any condensation dripping from under the car.

With either the regular outside air or with the A/C on, the air temp flowing into the car seems to be the same when I sent the digital temperature to 60 degrees (the coldest setting I can get).

It almost seems like I am getting R-134 flowing through the system, but am not getting any air to pull across the evaporater core? Would this be a door inside the ducts that may be stuck or binding?

I have not tried getting any fault codes, etc.

Any ideas or assistance would be greatly appreciated. Thanks.

 

[master486]

Seeing as you have the liquid line becoming cold and developing condensation, it would seem that the actual compressing system is working fine. Don't take the fact that you didn't see water draining from the evaporator case as a sign that the system isn't working right. It could be caused by a number of conditions including the weather conditions outside.

Sadly the self-diagnostics of the SATC unit aren't the greatest for catching a problem with the system. From what you describe, it sounds like the blend door actuator or the blend door itself is not going to the full cold position, or the in-car temp sensor is reporting the wrong information to the SATC control unit. But, you might as well try the diagnostics and see if anything turns up.

To enter self test, position the blower control knob at AUTO and the Function Selector Knob in either PANEL or FLOOR.

Then, press and release the COOL and OUTSIDE TEMP buttons simultaneously and, within two seconds, press and release the WARM button. The display will show a tracer segment going in a counterclockwise direction in the center of the display window during the self test.

When the self test is completed, DTC's for any fault will be displayed in the VFD Window. If no faults are found, all display segments will illuminate.

To exit Self Test and RETAIN all DTC's, press the COOL (BLUE) button.

To exit Self Test and CLEAR all DTC's, press the OUTSIDE TEMP button and then, press the WARM button.

After exiting the Self Test, the ignition should remain ON for at least 25 seconds to allow the temperature blend door actuator to calibrate.

Trouble Codes
24 - Fault in blend door calibration during self
25 - Intermittent fault in blend door calibration
30 - Self test indicates in-car sensor shorted
31 - Self test indicates in-car sensor open
40 - Self test indicates ambient temperature
41 - Self test indicates ambient temperature
42 - Ambient temperature sensor intermittent short
43 - Ambient temperature sensor intermittent open
50 - Self test indicates sunload sensor short
53 - Sunload sensor intermittent short

If any Trouble Codes appear during the Self Test, follow the diagnostics procedure given under "ACTION" for each Trouble Code given.

The Self Test will detect faults in the system temperature and blower speed control functions found during the Self Test and will display these codes in addition to intermittent trouble codes for faults that occur during system operation. The vehicle interior temperature must be between 10°C (50°F) and 32°C (90°F) when performing the Self Test. If the temperatures are not within the specified ranges, false in-car temperature sensor trouble codes will be displayed.

If no DTCs are generated as a result of the self-diagnostic test (88°F°C code is displayed), determine the conditions and go to the Symptom Chart.

 

[Dusty]

Sounds like you are low on 134a. Low pressure switch is cycling hense on/off. Get a bottle with a guage and check it out.

 

[MattN]

Okay, got a gauge and bottle. The pressure is between 25-45 at the low pressure switch when the A/C is cycling on and off. IIRC, that is supposed to be within limits and means I have a correct amount of R134.

Would the next step be checking the low-pressure switch?

TIA

 

[Dusty]

25 is the cutout point, you are low. Add some refrigerant until it stays above 30