EATC (automatic temperature control) Problems

[ians952]

I need some help here. First off, I have a 97 EB 5.0L with automatic temp control (EATC).

I have been having some problems with my EATC. My blower fan was only operating when I manually set the control to max, and the rest of the settings don't work. So I do a search, and I find this thread here: link. I did what it says and bought a new electronic module and spliced it in. Now my blower fan is on full no matter what and I can't shut it off, even if I push the power button on the interior interface.

I've checked all the fuses for the EATC and everything seems fine. I even got a second part from another source just to see if I got the wrong one, but nope, same part number.

Can anyone help me out here? This is starting to drive me crazy, and I can't really operate my Ex without a heater in the Canadian winter!

 

[ians952]

Any ideas, anyone?

 

[budwich]

from your description, its not obvious what you replaced the electronic motor control and eatc electronics???? And not sure why you don't have a heater... you say the blower is always on so you should be finding heat.

further please tell us which wires / pins you "spliced" together.... me thinks you have a wiring error.

 

[ians952]

Sorry, don't mean to be confusing...

The A/C blower was only working when the switch was placed in the "Max" position. I had heat/cold, just no fan. So I changed out the electronic module which controls the fan in hopes that it would fix the problem. It didn't -- it added another problem. The fan is now blowing max setting, regardless of what position I set the the switch to inside the truck (even the off position).

It sounds like the part is incorrect and is causing the fan to be switched "on" no matter what. But I checked with the dealership, and this is the part number they recommend.

 

[budwich]

Ok... but you said you "spliced in the module", please indicate what splices / pins on the connectors that you connected together.... (ie. check your wiring)

 

[ians952]

Ok... but you said you "spliced in the module", please indicate what splices / pins on the connectors that you connected together.... (ie. check your wiring)

Didn't really splice in a new module, just a new plug. The plug on the new module was different than the old module.

I used a pinout diagram that I got from Ford to match up the wires from the old wiring harness to the pins on the new module.

This is getting me thinking....:scratch: I assumed the pinout diagram was for the module. What if the pinout diagram was for the plug? I would have all the wires backwards... and probably lead to erratic behaviour of the module. I will have to try this when I get home.

 

[lvis82]

i had the same problem with my blower and i just replaced the resistor or whatever its called. its the little wire harness located in the engine compartment on the blower fan housing right next to and just lower than the actual fan. i would maybe suggest putting your system back the way it was and change out that resistor. got mine out of a junkyard.

 

[ians952]

As I figured, I had the wires reversed for the plug. Fixed that and the blower speed controller now works perfect.

Just for future info, I got the part from Rockauto.com, Part # RU539 -- cost $70. It is the exact same part as you will get from Ford with the same manufacturer and same part number written on the side of the part. Ford, of course, wants over $400 for the part.

For those of you who are replacing this part for model years pre-1998, you will have to use the 1998 module. You will have a hard time finding the part on the 1997 and earlier parts catalogs, I know I did. The one for 1998 works perfectly.