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EATC blend door actuator


Well-Known Member
July 20, 2007
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san jose, ca
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so i probably did a stupid thing (at least i hope so otherwise it will be a PITA to find), i'm in the process of installing EATC in my truck and I have all the parts and I bought a new actuator due to it's infamous problems. well the intial combo of EATC parts I got was from a '95, I wanted the nicer looking '98 to blend in better as well as being linked into the OBDII system.

so i'm testing everything out with the '95 head unit and everything works fine except for the blend door actuator (which i now realize I had hooked it up as if it were a '95-'97 unit, with the +/-12v being sent to it that earlier units required.), i don't think anything of it until the '98 head unit comes in and i spend an hour or so hooking it up on my workbench to test it out, and i still get the 024 error code.

so my question is, would hooking the '98 actuator up like the '95 actuator (with the +12v,ground) fry the actuator/servo? thanks for any insight on this

here is the link to N3ELZ's page on this

p.s. the pinouts on the back of the head unit are wired to '98 standards, the only error code is the 024.

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I am taking out my tranny to rebuild this weekend, but I'll get to this for you and try to figure out what's going on. Off the top of my head, I don't know that you would have fried anything except for an outright reversal of polarity to something.

I understand you're getting the error code, but some additional information about whether either servo moves at all when properly hooked up would be helpful.

The servo's are more or less "supervised" as to their position via potentiometer feedback. Unlike the units for non-EATC which use the position feedback internally, the EATC servo unit is really just a dumb positioner which reports it's position to the head unit.

That being the case, if the unit moves, but the error persists then chances are your feedback isn't working. I can see the possibility that the feedback output might get burned up by improper application of power.

I think the head unit is probably not bad -- especially if the unit tries to move the servo.

Like I say, this is going to be a busy 5 days as I finish off the SAS snd 4x4 conversion of my Ranger but if I get a break I'll research this for you.

I'm sorry you had this problem. My writeup is almost "too complete" sometimes and I know the level of detail can be confusing -- but I just didn't know any other way to approach it. I hope nothing I did led you astray.

Thanks for your comments in the PM!

hi john-

thanks so much for taking the time to respond. the servo doesn't move at all, one thing i just remembered though is that i have the connector for the 95-97 actuator, which means it is probably wired wrong, DOH! :banghead:

i'll research what i can about wiring it up correctly, but any links you might have i would greatly appreciate. fyi on the 95 HU i got error codes 24 & 25 but on the 98 HU i only got error code 24.

i was rebuilding my tranny a few months ago so no worries, i understand, and your writeup is great, i wouldn't be at this point even if it wasn't for it. thanks again.

since john is busy at the time I was wondering if anyone had wiring diagrams for a 95 ford explorer, I'd like to know which wire colors correspond to which pin numbers on the connector to the blend door actuator / servo . I already have the '98 diagrams but the colors have obviously changed so I have no clue which pins are which. thanks!


i just received my second actuator and still getting the 024 error code, both actuators have been new aftermarket dorman parts, could this be the problem? i've checked my wiring several times and all is good

^^is the one i got...

when using my multimeter i clearly see that I have the +5v being sent to pin 6, with the ground at pin 5. there is also a 4.48v reading between both pin 6 (+5v) and pin 7/8, which are the cw and ccw wires. i've done the self test several times and all i get is the 024 error, everything else works perfect except the actuator! any ideas anyone?

does anyone out there know anything about the circuits for the EATC blend door? i attached pics below of a view of the top and bottom of the circuit board, I've tried it several different ways with no luck, but if i directly attach the +5v and ground to the motor (with resistor) it spins fine until the travel limit is reached, any help? please.


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so i don't know if anybody is bothering to read this or just that no one has a clue, but this is getting really frustrating, the wiring diagrams sold to me were wrong, i got the entire system running fine on my workbench, even had an led hooked up to the resistor, but once i finish installing it it gives me the "888" code to indicate everything is fine...

but it's not, now the fan won't blow at all, it did for a second when the ground connection slipped out (until i reattached it) but i can't get any fan action, i am too tired and cold to finish this up today but does ANYONE have an idea as to why the diagnostic test says everything is ok, but the fan won't blow any air whatsoever.

so i don't know if anybody is bothering to read this or just that no one has a clue, but this is getting really frustrating, ..............does ANYONE have an idea as to why the diagnostic test says everything is ok, but the fan won't blow any air whatsoever.

The electrical systems in todays cars can be very complicated, which you of course already know, but that may be why your not getting alot of response. I know alittle about the electrical system but just by reading your post you know far more than I do. ABout the fan though, not to sound arrogant, but is the fan motor still recieveing power? If it is it might just be the simple problem of you mototr blew out.

thanks for your reply, i know that not many people know much about car electric's other than hooking up a radio or some led's but i was hoping someone who did the mod before would have some advice, after many hours of troubleshooting i have determined that first my fan motor is still working fine, but that i had two problems, somewhere between the workbench and the install the blower motor resistor decided it would be the perfect time to die (a $130 replacement part). and second, my relay to turn on the fan power wants to see a ground, but my EATC head unit (from the exact same model year) wants to put out 12v, so now i need to either put in an additional relay or maybe swap one out?

so a question if anybody knows the answer so i don't spend hours tinkering, can i just swap in another relay? i'm not sure about this because it would be receiving +12v from 3 sources (always hot, hot in run, eatc signal) or maybe could i switch the hot in run and EATC signal outputs? so basically the EATC output goes to where 'hot in run' is now, and where the EATC output should go would be a direct connection to the battery, thus allowing my ground, but the EATC won't trigger it unless it's on? sound right?

also on a side note, Torrie from is SUPERB at customer service, I highly recommend him to anyone looks for replacement parts, i have had it with the local dealerships in my area, not one of them are trustworthy and they could care less about service, all they want is for you to buy a new car every year, so save yourself the hassle and the money.