A/C Question

[BillyL]

Just spoke with a fellow 2004 T-Bird owner who is not. His car in the shop because air conditioner stopped working. The shop was able to jumper the compressor connections and cause the unit to start. The shop is telling him one of the car's computers is not allowing the unit to operate and is trying to locate a replacement computer. The owner did not know which computer. Personally, I have never heard of a computer related A/C failure. Has anyone else had this problem and what was the fix? For now, my only advise to him is to have his computer repaired rather than replaced and gave him the repair sites reference here in past postings.

[007Cruiser]

I vaguely recall a mention of this in the past. Kinda makes sense as nearly everything is switched on or off by one of the modules.

[steelblue5505]

The AC clutch get its power signal from the AC clutch relay located in the auxiliary junction box which the fuse box under the hood pass. side. There is also 2 fuses in this same box that control part of the AC system they are F1.11 15amps & F1.01 10amps. The off/on signal for when the AC clutch should come on & off is controlled by the Powertrain Control Module, the Automatic Dual Control Temp module and the ambient temperature sensor. Any of failure of these items will keep the AC from operating.

The Automatic Dual Temp Control unit has a built-in diagnostic program. When this program is run it will end showing fault codes if there are any. Running this program should help pinpoint the problem.
Below is the Self Diagnostics Procedure. Hope this helps. It should be done before doing anything else, easy to do and doesn't spend any money. If it shows codes the codes can be Googled and help getting the problem fixed.

2004 & 2005 DUAL AUTOMATIC TEMPERTURE CONTROL SELF DIAGNOSTICS

The DATC module self-test will not detect concerns associated with data link messages such as engine coolant temperature or vehicle speed signals. The diagnostic tool must be used to retrieve these concerns.
The vehicle interior temperature should be between 0-32°C (32-90°F) when carrying out the self-test. If the temperatures are not within the specified ranges, false temperature sensor DTCs may be displayed.
The DATC module self-test through the front panel display:

Can be initiated at any time. Normal operation of the system stops when the self-test is activated.
Is entered by pressing the OFF and DEFROST buttons simultaneously and then pressing the AUTO button within 2 seconds . Record all DTCs displayed.
Concludes by reporting all on-demand DTCs. Follow the diagnostics procedure given under ACTION in the DTC index for each DTC given.
Reports individual on-demand DTCs as 4-digit DTCs (less the alpha character).
Will calibrate all the mode doors and check all analog inputs. The DATC module will only report on-demand (hard) faults that occurred while the DATC module was conducting its self-test.
Will light all control panel display segments if no faults are detected.
Will report individual on-demand DTCs without the °C symbol lit.
To exit the self-test, press the DEFROST button. This will clear all on-demand codes from the DATC module memory. If no button is pushed, DTCs will continue to be displayed.

Upon exit from the self-test the DATC module returns to operational status. The DATC module executes a hard (cold boot) reset which places the DATC system in the OFF mode.

If a condition exists but no DTCs appear during the self-test, GO to Symptom Chart Condition: The DATC System Is Inoperative, Intermittent or Incorrect Operation. See: Diagnosis By Symptom

Always exit the self-test before powering the system down (system turned OFF).

Front Panel DATC Module Display - Retrieve Continuous Diagnostic Trouble Codes (DTCs)
Continuous DTCs are fault codes recorded by the DATC module which have occurred during normal operation. For the DATC module this means that all faults (intermittent or hard) that occur while the module is in an operational state shall be reported as a continuous DTC.


To retrieve continuous DTCs, press the OFF and DEFROST buttons simultaneously, followed by pressing the RECIRC button within 2 seconds .
The DATC module will report all continuous DTCs to the vacuum fluorescent (VF) display.
The DATC module will not carry out a self-test; it will only display continuous faults codes which are stored in memory.
All VF display segments will light if no faults are detected.
Individual continuous DTCs will be reported with the °C symbol lit.
DTCs shall be reported as a 4-digit DTC (less the alpha character).
Pressing the front DEFROST button will exit the retrieve continuous DTCs mode and clear all continuous DTCs from DATC module memory.
Pressing any other button (other than DEFROST) will exit the retrieve continuous DTCs mode and maintain all continuous DTCs in DATC module memory.
Upon exit from the retrieve continuous DTCs mode the DATC module returns to operational status. The DATC module executes a hard (cold boot) reset which places the DATC system in the OFF mode.

[Will]

When my a/c quit, it was the CCV (coolant control valve) that had given out. That was on the way to TBN's Savannah cruise-in. Had the CCV replaced at the local Ford dealer ($$$) & it's been fine ever since. ---Will

[BillyL]

Thanks Guys, especially steelblue. Your info is way over my head, but I did cut and paste it into an email to my friend. I also suggested he start with changing the DCCV as it seems to be the most common cause of failure. When mine failed two years ago, it started blowing hot and cold air but did not quit as Will's did. I also suggested he find a mechanic more familiar with our birds. His car is now at a small local ford dealer's shop. Just hope they have not already pulled the computer!

[birdfan]

I had a strange issue that may, or may not, relate to your friend's.

My EATC (Electronic Automatic Temperature Control) went blank and would not work at all. I could not do the EATC code check since it, and the display, wasn't working. I was looking at the ordeal of either getting a new EATC (surprisingly listed on Ford parts sites, $$$) or sending it out for repair when I decided to do the old practice of checking fuses first.

The EATC fuses are in the central junction box (passenger kick panel) and there are two fuses that relate to it (#F2.20 and F2.29). I pulled #29 that is only EATC and it was good. I pulled #20 that is for FEM and EATC and it also looked good. BUT, when I pushed it back in the vent doors did all their "cycling" and the EATC came back alive.

This is a mystery to me since the fuse was not blown and had been in securely (was very hard to pull out). But all has been working since.

So, moral of this long story - check all fuses and relays first. You might get lucky.

[steelblue5505]

BillyL,. In your 1st post you told us that the AC compressor was not operating ,but could be made to operate by applying voltage at the compressor.
If the DCCV was the problem as you are now suggesting the compressor would operate normally & the AC would function as lt should, BUT the air movement would feel hot due to the failed valve allowing hot coolant into the climate control. The AC's cool air will never be able to col the hot air.
So if indeed the AC clutch is operating when AC is selected than it could be the DCCV but if the clutch isn't operation than it is doubtful the DCCV valve is the problem.

[BillyL]

The problem was the DATC module failed. The shop located a used module that tested good for $200.00. The owner has kept the old module and will look into having it repaired if needed for a backup .Thanks again to steelblue. Your first message and my shop manual helped get the mechanic in the right direction.

[007Cruiser]

You would think that a competent repair shop could spend a few bucks to get the information on line.

https://www.alldata.com