Any Automotive A/C gurus here?

[metallicats33]

Just wondering if anyone here has some knowledge of automotive A/C, particularly Ford's EATC system. I got one that's giving me the run around.

[illshou]

I work in a shop that specializes in automotive a/c, what issues are you having? I've owned quite a few fords myself as well.

[metallicats33]

well it all started as a simple accumulator replacement. recovered the system, replaced the necessary parts, vacuumed, leak checked and re-charged to spec. The compressor would not turn on even when jumping the low side switch. Did some simple test and found no 12v coming out of the EATC at the a/c compressor out pin. Ran the On-board diagnostics and got one code for ambient temp sensor open. inspected the wires and OHM checked. All looked good so I cleared the codes. A/C now worked perfectly... for about 45 min I ran the on-board again and got 2 codes for blend door motor fault. Now this is where I'm stuck. I'm back to no 12v at a/c compressor out pin, The clutch won't engage when jumping the low side switch (naturally) And when the Proper pins are jumped for the Blend door motor it functions both ways, all related pins OHM as per Ford's trouble shooting steps. Now I'm not too familiar with EATC but shouldn't the clutch still engage even with a faulty blend door motor? And probably the most important part... the on-board diagnostics will not give me codes any more. All I get is the following screen:

I'm At a loss... Everything worked great until the accumulator needed to be replaced. The system never got below 1.5lbs of charge and nothing electrical was touched during service other than the low side switch.

Thanks in advance for any insight,
James

[fordtransman]

1. Year/Model?
I would like to follow the wire diagram and give you pointers on how to
verify that the EATC is bad. Your low switch is 3 wires? (Need the car)

2. Why was the accumulator replaced?
Did the bag come apart? Was the system "Flushed with solvent" or just evac and filled?

3. EATCs have a "calibration process" Not sure what "Ford test book" you are using.

4. When a module "jumps codes around" and then lights up the entire screen its usually bad.

5. At 800 bucks, EATCs are pretty pricey (new) do you have a local wrecking yard where you can pick up an EATC?

I am a Ford Master Tech, both Drivetrain and Chassis (includes A/C)

...Gregg

[fordtransman]

Have you verified proper system pressures after the refil? On the low side we have a "Cycling switch" on the high side we have a "high pressure cutoff switch" If the system was overcharged, the clutch coil will not activate by normal command from the EATC.

[illshou]

It does sound like the etac is bad. The comp will turn on when the blend door is non operational,the blend door motors or the door itself go bad all the time.
Another common problem depending on the model of car was the large relay box that houses the relays for the a/c, fuel pump and other stuff. Used to find alot of them bad as well.
Another quick test is to chack for 12v at the pressure switch. Make sure there is power there.
Jump the switch over and check for 12 at the compressor. If it does have power tap the end of the comp with something like a broom handle. It is common for the clutch disk to wear and have trouble ingaging.
Also the compressor clutch can be bad and
go open circuit when it heats up

[fordtransman]

Of course I dont know the year or model yet... Some years/models have another module in the loop besides the head unit you see. Its quite possible that a failing/failed EATC caused the system problem you have to repair. (accum)

Once I get the year/model I will be able to better process what is going on... Right now, I see a failed EATC

[fordtransman]

The key for me, is that it was written " the A/c system worked fine for 45 minutes " Shouldnt really be an overcharged system, or airgap on the compressor clutch. Still seems like a control problem.

Of course "worked fine" to me is MAX a/c, 20-30 degrees cooler than ambient coming out of the center register.

[metallicats33]

thanks for the replies guys. Fordtransman, It's a 97 Crown Vic non CNG. 2 Wires at the cycling switch. I just removed the ambient temp sensor and ran the OBD again. THis time I got the two codes related to it so I'm assuming the image I posted above occurs when no codes are present? And yes it worked for 20 min in the drive way and about 20 min around town. duct temp was around 25 - 30deg center and ambient was probably around 65 - 70 deg. It stopped working when I took it off max A/C and pressed Automatic. Don't know if that was a coincidence or not.

[metallicats33]

The accumulator was replaced due to rust. The system was flushed properly and inspected for any other failed components. No other rusted components were found. The orifice tube was replaced and the system was charged as per the model year. I can't jump the cycling switch but if I give it direct 12v the compressor turns on. I've ruled out a bad A/C compressor out wire by pinning a wire and running it directly to the switch ( not the easiest way but I gotta improvise when im not at work) The wire is not getting 12v out when it should. What else do you need? I'll try and rembember everything I've checked/done, A/C is not my specialty and after getting up behind this dash and those horrible clips I had to remove to access the ambient temp sensor, I sure miss my 69'


Thanks again,
James

[fordtransman]

I have a 06' Crown Vic myself... So on Max AC the system works completely normal? The ambient sensor has to tell the EATC the outside air is 50 degree F or more before it will allow the clutch to come on. The Ambient sensor is the one on the radiator core support.

There are 2 sensors INSIDE the car... the on the dash is the SUNLOAD, and the one behind the dash is the Automatic Temperature Control Sensor

You are getting a DTC for the AMBIENT sensor? Thats outside. Usually a failed "open" thermistor will show -40 F degrees through resistance translation.

The EATC sends a feed to activate the a/c coil if all EATC inputs are ok, but the PCM still has to allow it... "denys it under load, engine temp...etc"

So, you mentioned chasing a sensor under the dash...

Go check the one on the Core support. Maybe it was "bumped" or a wire accidentally tweaked. If the A/C system works normal on MAX AC dont mess with the "refrid system" anymore... cycling switch, compressor, etc... Relays, etc... thats not the problem.

[fordtransman]

The EATC On-Board Diagnostic will detect concerns in the system control functions found during the On-Board Diagnostic and will display DTCs and intermittent DTCs for concerns occuring during system operation. The vehicle interior temperature should be between 16°C (60° F) and 27°C (80°F) when performing the On-Board Diagnostic. If the temperatures are not within the specified ranges, false in-car temperature sensor error codes will be displayed. Record all error codes displayed during the test.


Here is the diagram... Notice the shared ckts for the Sunload and the in car sensor... So the problem with the Ambient sensor dtc is either the sensor itself, the signal on CKT 767 Lightblue/orange tracer or the EATC.

[fordtransman]

metallicats33


I just noticed you are in So Cal too?


Its a Small World After All.

I am near the I15 and I10... where are you?


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I am a fan of Metallica, but its Nine Inch Nails that have the 27 Halos of...

[transamman908]

If all else fails

[metallicats33]

Gregg,
My work is out by the 10 & 215. I live in the Covina area. Thanks for all the help. No, The A/C does not work on any setting. After I got the A/C to work it was only used in the max setting. The instant I pushed that Auto button it stopped... Coincidence? The Ambient Temp code only came on once and that was after servicing the accumulator. I inspected the connector at the upper radiator support and everything looked good so I cleared the codes and the A/C worked. When the A/C Quit the second time (current) I got codes related to the blend air door motor, but when I jump the pins 21 & 22 at the rear of the EATC the motor moves freely both ways. I cleared those codes and they have not come back. What concerns me is I can't jump the cycling switch. I have checked everything except for the diode on the compressor... at least I think I've checked everything