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-   -   Help Diagnosing AC/Heat Being GONE! (https://www.f150online.com/forums/2004-2008-f-150/520471-help-diagnosing-ac-heat-being-gone.html)

casslaw 03-12-2019 10:42 AM

Help Diagnosing AC/Heat Being GONE!
Hey Guys, this one has me 100% stumped! On my 2004 Lariat Screw my ac just stopped 2 days ago. The screen (I have the numbers on my center console) keeps changing back to 75 every time I get out of my vehicle, almost as if the ac controls donít remember where they were set.

Now, I have NOTHING! No heat, no ac, zip! I have checked every fuse, relay and ground. Everything is fine. The oddest thing is that there is NO power at the blower motor relay, at the blower motor, at the blower motor resistor.

That lead me to believe the actual ac/heat head unit is bad and isnít sending the signal to the relay to turn the fan on. Problem is, Ford and everyone else tells me that this part is discontinued!

I have NO idea what to try next. All fuses good, all relays good, No power to the blower motor relay, blower motor resistor, or obviously the blower motor.

Please help!! Oh, ya the AC is cycling...I can feel very cold air coming through the vents but the fan motor isnít being told to turn on! ANY help is appreciated! Chris.

casslaw 03-13-2019 04:06 PM

Well this is BAD news! I took my truck to the dealer since I wasn’t getting power last the relay in the fuse box. I just received a call telling me that one of the ”mini computers” on the back of the fuse box is bad. The entire fuse box needs to be replaced, keys reprogrammed, etc. This truck has given me 15 years of relatively trouble free use but now it’s going to cost at least $900 to fix it. I feel helpless. Having a brother that works for Ford in Dearborn I have always had the knowledge I needed to fix anything. Not this time.

Fifty150 03-13-2019 11:56 PM

Does your bad fuse box have anything to do with the dead A/C & heat?

You may be able to buy the parts and replace the fuse box yourself. Then you will have to find a way to program the keys. If the dealership wants $900, what will it cost you in parts if you do it yourself?

Roadie 03-14-2019 10:34 AM

get one from salvage yard

Patman 03-14-2019 11:10 PM

you also could probably wire around the fuse box with your own relay if you're electrically handy

casslaw 03-15-2019 02:20 PM

Originally Posted by Patman (Post 5248193)
you also could probably wire around the fuse box with your own relay if you're electrically handy

My steering wheel AC controls and the lights on the AC unit in my dash were also not working so I was thinking it was an electrical issue but I couldnít believe it would be the fuse box!

I spent about 6-8 hours attempting to diagnose this issue. My brother works for Ford in Dearborn and my other brother has an auto repair shop here in Tampa so I was in good hands. The issue was that we were not getting any power or ground at the fuse, relay, ac resistor, blower motor...nothing!

I was told by the tech that there are a number of body ecmís for a lack of a better term on the backside of the fuse box and that those are what went. Thatís the reason my lights are acting odd, my interior lights are working on and off, and the ac blower motor isnít getting power from the fuse box.

I do have my doubts. This could easily be a bad wire or two causing this issue, but itís out of my control right now. Iím hoping theyíre right and it is the fuse box. I had to drop off both keys so they can be programmed to the new BCM connected to the fuse box.

I joined his forum in 2004 when I bought my truck and this place taught me everything about my truck! This forum has been great for me, but I have never read of this issue. That has me nervous Iím about to drop $900 on my 15 year old truck but frankly she has 195k on her, has treated me great, and is still in great shape!

Ill keep you guys updated on Monday night when theyíre done.

Patman 03-16-2019 01:58 AM

gotcha. good luck!!

So together we've got almost 30 years on the forums :eek:

Fifty150 03-17-2019 01:42 AM

Originally Posted by casslaw (Post 5248195)

I have never read of this issue.

15 years ago, when the 11th Generation trucks were new, you only heard about how great the new truck was, and what kind of mod worked or didn't work.

It seems like the fuse box is now developing into an issue. An issue without specific cause, just age, wear, & tear. Nothing that someone can do to prevent it from failing. And different failures have caused other problems. I just read, I forget on which forum, maybe this one, how a bad fuse box was why the OBD II port & cigarette lighter port was not getting power.

Originally Posted by casslaw (Post 5248195)

That has me nervous Iím about to drop $900 on my 15 year old truck

Still not too bad. A lot of us are still spending that much, and more, on tires. I just spent $XXX on a new radiator. But that was my fault. I stabbed my radiator with a knife.

SoonerTruck 03-18-2019 10:41 AM

Originally Posted by Patman (Post 5248214)
gotcha. good luck!!

So together we've got almost 30 years on the forums :eek:

Pushing almost 45 with me in the mix.

Patman 03-20-2019 03:12 PM

Originally Posted by SoonerTruck (Post 5248285)
Pushing almost 45 with me in the mix.


casslaw 03-20-2019 05:28 PM

Well I guess this is the happy ending! I got my truck back yesterday! The fuse box/BCM was definitely the problem. My brother says he doesn’t see it often and usually with 4wd trucks that have seen water. Mine is 2wd and has never been flooded in any way.

Once the dealer got the BCM installed they started getting ABS and BCM/PCM communication codes. Not what I wanted to hear! I talked with my brother and the tech. I suggested taking the BCM out, checking the pins, wire connections and reinstalling it. It took him an entire day to do that but it cleared the codes!

I picked her up last night, but the AC control module (dash ac controls) weren’t working correctly. In order to get the ac to come out of the vents, I had to push the defrost button. Somehow I found one at a local salvage yard. $108 with a lifetime warranty...couldn’t pass that up. I made sure that me installing the ac control module wouldn’t affect the dealer’s work in any way, they put it in writing.

I just installed the ac controller and everything is now working perfectly again!

Well, not perfect, I still have a low grade misfire that acts up when I tow my boat...throws a P3025 code. I can’t nail it down. I just redid the entire timing chains/tensioner/head gaskets/etc when I broke 4 plugs off last August. At first it was throwing a code for cylinder 8, so I swapped coils to see if the problem followed and now I’m getting a generic misfire code or the bank 1 sensor 1 code.

Im going to change my fuel filter to eliminate a fuel issue then most likely post a new thread.

Yes, some of us have been here a LONG time! I don’t post a lot but this place taught me everything about my truck! Taking it to a dealer hurt my pride but it was the right thing to do. Thanks everyone!

To answer some questions, yes the BCM fixed the ac issue, the lights that weren’t working in my center console, everything that I had noticed was wrong. As to what caused it, I can only guess age. I’m only at 196k and she’s held up great. Most issues were self inflicted.

Roadie 03-20-2019 05:41 PM

Really glad you got-er fixed!

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