Any Automotive A/C gurus here?

[fordtransman]

As you can see in this diagram, jumping the cycling switch will not do anything. All the switch does is allow the voltage potential 12v sent to it by the EATC to continue to the high pressure cutoff switch. If anything, you would want to introduce 12v fused power to the Pink with light blue tracer wire on the cycling switch connector (unplugged from the switch) and see if the compressor clicks on. (assuming the WOT relay is closed by the PCM at the time)

You wrote in your last post that on MAX A/C everything was fine, you switched to AUTO and its been broken ever since?

At this point if you have checked all your inputs...and verified the function of your outputs ( at the EATC pins ) go ahead and replace the EATC.

[metallicats33]

I have supplied 12v to the tracer wire (PK/LB), The Clutch engaged and the A/C blows cold. At this point I believe the only items I have not checked are B+ at Eatc connector, Circuit 298 & The A/C Clutch diode. Gregg I thank you for all your help and input. I'm not an A/C guy and electrical was never my strong point I'm sure your right about the EATC. I have included a copy of the diagram I had gotten for the 1997 crown vic that includes the pin out for the EATC. I have followed a path, could you please verify I have done it correctly?

1) Verified System is Charged to spec
2) Jumped the pins at A/C cycling switch Connector = nothing
3) Supplied 12v to the AC Cycling switch connector (PK/LB) to verify A/C Clutch operation = Clutch operational
4) Checked for B+ at A/C cycling switch Connector, Circuit 348 & Checked for B+ at A/C pressure cut-off switch Connector (PK/LB) = nothing
5) Checked for B+ at EATC module Pin C228 , Circuit 348 = nothing
Now I believe the next step would be to check for B+ at Circuit 298, Ignition. If I have 12v this should confirm failed EATC?

Thanks again for the help,
James

[fordtransman]

(going over your diagram now)

The diode is just a one-way door. You can check it with a DVOM ( Im sure you know that) If the diode is bad, (allows voltage to flow both ways) the secondary kickback spike from the compressor clutch may have smoked the EATC.

(for anyone else viewing)

When the clutch (electromagnet) is energized, its creating a magnetic field around the primary windings. When the coil is shut off, the field collapses, and sends a MUCH HIGHER secondary voltage right back up the line... poof! Thus the diode for protection.

Therefore, go ahead and check the diode... before replacing the EATC.

[fordtransman]

B+ at Circuit 298, Ignition

Check both... pin 11 and 26.

As long as pinpoint tests verify the input for the Ambient is above 50 degrees F while the EATC is not energizing the compressor coil output on max ac or auto... and dont forget to verify the Diode. You dont want to smoke another EATC

Replace the EATC ( find a known good used one )

[metallicats33]

Thanks, I will finish checking when I get home today. Recommend any good wrecking yards?

[fordtransman]

Side note: I talked to one of our fellows that has been doing Ford A/C since the 70's...

He said the EATC doesnt care about any inputs other than power and ground to send the 12v to the cycling switch on MAX AC.

So if the ignitions are 12v, check them with the ground pin (verifies ground) and with MAX AC on, if you dont have 12V out to the cycling switch..

Bad EATC

***
Its been a long time since I have been to any yards. I used to go to Ecology off of Riverside, south of the 10 in Colton/Fontana and the Ecology off of Cherry in Fontana. I stopped going to the Pick A Part in Ontario...all they have is miles of Caddys and Buicks.

[metallicats33]

So if the ignitions are 12v, check them with the ground pin (verifies ground) and with MAX AC on, if you dont have 12V out to the cycling switch..
Bad EATC

Perfect, Sounds simple enough. When I can get my hands on the car (Wife doesn't like driving mine ) I'll check Powers and grounds at the EATC. Your right about the Pick a Part in Ontario, I went there a few weeks back looking for a turn signal switch for my blazer... waste of time. A guy at work said he can get his hands on a EATC from a 96, the face is cracked in half but he says the internals are ok and the A/C still worked. I figure it can be a good test EATC / Temporary fix until I can find one cheap. $800 is just too much

Thanks again for all the help
James

[metallicats33]

Ok,
So I checked the diode = good
Checked 12v to ground at the connector = good

I decided to take the EATC apart and this is what I found:

EATC1.JPG (26.28 KiB) Viewed 1753 times

EATC1.JPG (26.28 KiB) Viewed 1753 times

eatc2.JPG (28.03 KiB) Viewed 1753 times

eatc2.JPG (28.03 KiB) Viewed 1753 times

Now I've done some repairs on video game console boards, asuming the board has been damaged by the burn I'm sure I can still jump the relay pin to pin 25 without compramising "normal" operation. My only problem is I can't find that relay anywere that dosn't want an order of 1,000+ units I think the F5RF-14A640-CA is a Ford# and the G8SN-UA-007115 is the OMRON#. Any chance Someone might have some of these laying around in their shop?

[scottmac74]

The last good service P/N for the EATC module was F6VZ-19980-AB, (engineering P/N F7VF-18C612-BB <---this is/should be the P/N on the module's label) but it is now an obsolete P/N through Ford and no dealers are listing one on the obsolete parts locator, so you are going to have to go salvage yard on this one. According to FCA (Ford Catalog) 1996 or 1997 will work for your application. Try http://www.car-part.com, it is a salvage yard locator that lets you search for parts using a similar system to the networked salvage yards, (it will let you show the results by cost, distance, condition...etc.). I use it all the time at work when I need to locate a used part.

-Scott