AC Compressor gets no signal from EATC

[vektron]

Hello,
I am new to this site, and being reading many threads. There is a ton of information here and the best is, it is specific, but I am still not sure how to resolve this issue.
So I decided to post in the hopes a member can help me.

I have a '97 Ex EB 4.0L and my AC compressor is not kicking in. I was able to get the system to work by manually applying +12V on the cycling switch, which was recently changed due to refrigerant leak. The system has the correct pressure since I just had it flush and refill by a mechanic. Also shorting the cycling switch does nothing, there is no power coming in.

On the EATC side, everything seems to be working. I get hot air when I raise the temp, and ambient temp air when I select max AC. I also did the EATC self diagnostic, but only got 888.

One of the questions I have is whether the overhead console temp reading affects the EATC turning on the compressor? Mine is having issues since it keeps displaying -40 for the most part, but sometimes it jumps around. Thanks to this forum I know this is the ambient sensor by the grill, so I am planning on replacing it this weekend.

So here is my dilemma, has anyone here seen this?

Thanks in advance.

 

[budwich]

what happens when you set the system on manual with max ac .... in terms of display??? and I don't think you should be getting "ambient air" when in max ac (unless you mean recirculated).

Of course, you checked your fuses with a meter, right?

 

[vektron]

Hey budwich, thanks for the quick reply.
When in manual, It behaves the same. I can control the fan speed with no problem. The display has the fan icon showing then.

 

[budwich]

but I think the display is supposed to say something like "60 max". again check you fuses.

 

[vektron]

Yes, I do get the max 60 message.
I did check the fuses and the relay on the engine fuse box.

 

[budwich]

does your message center work???? lastly, when was the last time your ac functioned as "expected"?

 

[vektron]

Yup, the message center is ok, I get the miles, gas, oil life, etc....
It's been a couple of years now that the AC has not worked. The compressor used to cycle a lot on-off, but it appears that's normal. Eventually it just stopped cycling. I always though it was due to low refrigerant, so finally now I was able to have the system flushed, and I am finding out that the system works if +12V is applied before the the low pressure/cycling sensor.
I heard there is a diode also that blows, but not really sure where it is.

 

[budwich]

well, I guess you now have to "break into dash"... you need to check the voltages going into the control module. there are THREE... LG/Y (pin 12) hot at all times, BK/LG (pin 11) hot in run, and W/P (pin 26) hot in run. I assume one of the "hot in runs" gets switched to pull up your compressor but I don't know which one.... but again check all three.

 

[vektron]

Yup, that's going to be the weekend project. I'll pull the EATC out and check the signal. I believe pin 25 (P) is the one for the A/C Cycling Clutch Output. So hopefully I get a signal here as well.

Thanks for your help, I'll update the thread when I thry this.

 

[navyjx]

I have the same problem. Did you ever get it resolved?

 

[bobflood]

I have the same problem. Did you ever get it resolved?

I just solved this same problem recently. Check out this thread:
http://www.explorerforum.com/forums/showthread.php?t=363745&highlight=EATC
This solution worked for me, and it was surprisingly easy to do. The whole aasembly is easy to take apart, and the relay was easy to identify. My solder joints looked OK, but I redid all four of them anyway and ... Voila!