2012 EXP EL HVAC front blower no air movement - electrical diagram anyone?

[inmanlanier]

I've read several posts on this - only 1 mention of similar symptoms - no remedy posted.

We've got 115K miles on the OEM blower, resistor and wiring for the front AC zone. The other day it simply stopped blowing any air, in all fan settings. The 40A fuse is fine upon inspection. Inspection of both wiring connectors SAT (no evidence of burning). I've wiggled both connectors a good bit - no results. I've not tried to use a mirror and check the fan motor pins or the resistor pins. I get no voltage at any of the pin-outs on the wiring connectors themselves. I have checked voltage between different pins, and voltage from each pin to a ground. Zero.

Anyone have a wiring diagram and/or description of the control logic? For example, does the switch on the dash vary voltage to the resistor, or vary voltage to the fan motor until on high and then simply bypass the resistor?

Anyone experience zero voltage on all pins? On a slightly related note - how does one remove those big 40A fuses???

Thanks, all in advance.

 

[bb37]

The McDowell County (NC) Public Library website has access to the Chilton library of factory repair manuals including wiring diagrams.

Go to this link: https://mcdowellpubliclibrary.org/chilton-auto-repair/ and read how to access the Chilton library.

 

[inmanlanier]

thank you, thank you, thank you!!! This is wonderful. I don't feel that guilty because our extended family shares a home in Macon County, NC .

I'll develop my troubleshooting plan tomorrow and fill everyone in once I've tested. For all of your information, the fan switch on the dash does a selection of cascaded resistance on the 'resistor'. The resister is the path to ground. I figured the control scheme would be something just like this.

The yellow green wire energizes the +12V side of the fan motor at all times when you have the system on (i.e. AC or non-AC, but blower to be moving air). The fan switch selects various resistance values on the resistor to vary the fan speed.

The pink wire coming off the fan connects to two places - a) the top (i.e. highest resistance) of the resistor bank AND the high switch fan setting.

From there, the resistor is actually 3 different resistors in series with 3 takeoff points. If you have selected the high speed fan, the resistor is completely bypassed allowing the fan motor negative connection (pink wire) to go directly to ground via the contacts of the fan switch. This means a full 12V across the fan motor - max speed.

For all other fan speed settings, the resistor is in play. As you select down in fan speed (3, then 2, then 1) - setting 3 has only 1 of the 3 resistors in play, allowing a higher voltage (say 9V?) from the motor to ground. When you hit the 2 setting on the fan, now 2 resistors are in play, perhaps dropping the voltage across the motor to say, something like 6V. You get the drift.

I'll update the post once I finish and execute my troubleshooting plan.

bb37 - you're the best!

 

[drscanman]

I've read several posts on this - only 1 mention of similar symptoms - no remedy posted.

We've got 115K miles on the OEM blower, resistor and wiring for the front AC zone.

Run your VIN number at the Ford website. There was a recall for the front blower motor replacement. See your EL is listed.

 

[inmanlanier]

OK - will do. What little I've read about those recalls was for the later models - but I will check. Thanks.

What's odd in my case is that I had no voltage on any of the pins of either connector. There should have been 12V on one of the two motor conductors. Yesterday and today I was distracted with my car hauler (25 year old, some bracketry rusted). I hope to get to this tomorrow and see what's going on. Now that I know how it's wired, I'll be able to get to the bottom of it quickly.

 

[inmanlanier]

This was too easy. As I shared earlier, I couldn't understand why I got ZERO voltage on any of the pins. it made no sense other than a blown fuse or relay. I had not studied the fuse/relay chart enough in the owner's manual enough to realize there were BOTH a FUSE and a RELAY. This became obvious when I looked at the schematic that our prestigious representative bb37 posted for my use. THANK YOU BB37!!!

When I reviewed the diagram - I quickly concluded that other than a wiring issue (highly low probability of occurrence), the next likely thing was a relay failure (from my experience also highly low probability of occurrence). Since the fuse was in series in the circuit, I concluded it was much more likely for relay contacts to fail OR a coil failure before a fuse would blow.

Sure enough, today I went out there with the goal to simply pick a relay of same rating in the fuse box and switch it with the one for the blower (relay spot #3). Next to it was a trailer charging circuit (relay # 4) that I think we've almost never used because we hardly ever tow our electrically powered brake car hauler with this car.

What'd'ya'know - when I swapped relay in slot 4 with relay in slot 3 - voila - the blower worked fine.

So... the 'Hi-Power' relay failed. My guess is too many cycles in 13 years and 115K miles of South Florida driving. Now I have two replacement FoMoCo relays on order (so I have a spare) that will be here tomorrow.

I think I've had 1, maybe 2 Ford relays fail in my many, many years of Ford ownership (admittedly, relays I don't remember before the mid 80s) - but that was it. Of course, time will tell if there's an underlying cause to the relay failure other than end of life. Based on the lack of other symptoms (charred wiring, connector pins arc'd and diminished pin size, etc.) - I think Weibull has prevailed here (bathtub analysis - end of life - too many cycles).

 

[expeditionatnight]

Amazing, thank you for all your follow-ups, thank you thank you thank you. I had created my first post yesterday afternoon and keep checking for replies but then decided to read some random threads for something that might be relative to clue me in on my weird symptom and I think you nailed it. My blower motor works on max speed speed number four but there was zero voltage at the female connector for the resistor, I thought I was in the Twilight zone. I never thought of using the lower speed settings and then checking the voltage. It will probably be late tonight or sometime tomorrow before I could do that final check but I'm hoping the light you shed on this clarified the false negative I've noticed. I'll touch back!

 

[inmanlanier]

@expeditionatnight
Any update?

 

[Yupster Dog]

@expeditionatnight
Any update?

For a member to get an alert,
you must either quote post, like I just did you.
Or you can mention them by putting the @ symbol in front of of their name.

I fixed your post for you.

 

[inmanlanier]

I think thanks are in order . Are you saying that by putting an @ symbol in front of the poster's name, it sends them a notification?

 

[Yupster Dog]

Try it, You can just type it all the way or use the drop down menu that pops up.


notice you did not get an alert for this

 

[inmanlanier]

@inmanlanier test test

 

[BigOleFordFan]

Funny that this thread would pop up now, as I just yesterday had my '011 at the stealership for the same problem....no air blowing out, but I could feel that there is heat/cold air there, just nothing pushing it out into the cab or onto the windshield.....

Unfortunately, I am not able to do the type of investigative electrical or replacement work the OP did, or I would have just fixed it myself...

And it ONLY cost me $900....$350 for the motor, harness, & connectors....the rest was for LABOR

Oh and BTW, my relay(s) & fuse(s) were fine, probably because I replaced most of them back in '22 !

 

[inmanlanier]

Sorry to hear that! I understand the blowers/wiring do fail. I was lucky mine was only the relay. Very easy fix and quite inexpensive.