Originally Posted by
wickedbusa
The rear system seems to be working, but I can't really tell since I am always driving. I do however, notice that the AC will blow colder if I have the rear system on. Is the Excursion's cabin just too big for the front system to cool it down without the use of the rear system? If I don't have any rear passengers, I usually leave the rear system off since it drips water onto my MBRP tip.
In regards to the self diagnostic on the head unit, should it automatically show some kind of code if something has gone wrong?
Heating seems to work just fine if I have the temp cranked all the way up.
I live in Vegas and the front system is enough to keep the cabin comfortable. I'll only turn the rear system on when I have passengers back there. I'm more acclimated to the temps though, so if the cabin is 80*, that feels good to me when it 115* outside.
When you change the fan speed selector is there a definite change in volume with every commanded increase? I'm still not clear if you have a problem with discharge air temperature, or volume.
Here's a short vid on the EATC head unit self diagnostic feature. They won't always throw codes when they're bad.
Ford EATC Diagnostic Test (Self-Test) Procedure for Electronic Automatic Temperature Control Modules - YouTube
The dealer that fixed mine swapped in a new head unit to see if that fixed the problem, and it did. I went through all of the pinpoint troubleshooting from the factory manual which involved a lot of vacuum testing(which was very time consuming), and it didn't identify any problems.
You could still have a mechanical problem with the front evaporator, blower, or blend door also. Rule out what you can. Hopefully your charge pressures really are good. Adding the load of the rear evaporator, which then makes the front colder, is unusual.
If you've read the majority of EATC threads you've seen that troubleshooting them often leads down a rabbit hole. That's when an experienced Ford dealer tech is worth every penny you pay them.