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So I have been chasing my tail trying to figure out what is going on with my ac and heater. At one point I did have some air being pushed through the vents, but that stopped a few weeks ago. I just dealt with it until it started getting hot. I tested fuses and found 107 faulty (replaced easily enough) and double checked the others. Everything else and the relay for the ac and blower motor looked fine. Tested wires at the blower motor for power and found nada. Went to the resistor, bc that’s the next most common issue. No power there either. Turned back to the cab and pulled the dash off to look at the climate control. Vacuum is great and I could visualize everything changing like it should back behind the glove box. So not a vacuum issue.
Back to the climate control.....looking at temp selector and fan speed. NO POWER to any of those. That and the lack of power has me stumped big time. The other little side track is that the PO had a power cord spliced into the power wire coming out of the blower motor to the battery and the ground was also spliced. I undid this and removed the extension cord from the equation and spliced the wires back together. Still no power with key on. Google is no help. All the common things that come up are really all I keep finding. As I’m perturbed by this dumb PO I finally decide the only thing I can do is trace it all back on the harness. As I’m following it back from the blower motor I realize that part of the wiring harness was pushed back behind the turbo. The wires are STIFF! as I finally get them out I can see multiple areas that look like chipmunks have had their way with the wires. So that’s where I am right now. Slowly peeling off all the tape he had wrapped around this wire loom and going to replace each crapped out section with a butt splice or soldered back together with heat shrink over top. The wire harness that holds it up away from the engine was broke off so I’ll likely replace that with a used piece or just zip tie the wire harness up to the old holes. This has been entirely frustrating and probably part of the reason the battery keeps not holding a charge!!




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By the way, the Ford part number for the under hood wiring support that you are missing is 3C3Z-14A099-AA I am unsure if the part is available from Ford anymore but worth looking for in my opinion. If you gGoogle the part number I provided you will find severa sources where you can pick one up for about $40 plus shipping. Don't forget to obtain the plastic retainer pins. (y)
 

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So still havent figured out the blower. There is nothing happening when it is turned on. Nothing out the vents. No heat. No cool.


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Check for power at the relay in the power box under the hood. Usually not a problem,but one of my spades was broken off and worked intermittently .It's a long shot but thats where the power starts at for the blower.
 
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@ford_doctor ; I appreciate the part number. If I thought it would improve things considerably I’d do it. I’ve put it all in corrugated tubing with some electrician tape wrapped intermittently around it. Seems to be holding up nicely and is well away from any heat sources unlike before. I repaired the wires with equal gauge wire and things are back to normal there. Still no blower motor power. Next step tested the blower motor by removing it and hooking up to 12v. Works fine! So not the blower motor itself.

Tested wires to blower motor and no ground or power were present. I’ve checked fuses. Nothing. I’ve checked relays under dash and nothing. @BlueOx1 ; I think I’ve checked the relay in the power box under hood, but I’m going to need to look at that again. Hard to remember after so many fuses and relays.

Resistor for blower motor under hood looked fine and even if it was the culprit I should at least get some high fan speed air as it gets bypassed if it blows.

WHAT AM I MISSING??!!!!

This is so frustrating as I’ve needed the defrost twice now as it was raining and cold. Help!!!


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Okay, lets dig into this. We need to know what model year this Super Duty is AND is it equipped with electronic automatic climate control with push buttons or a manual climate control with dials?
 

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Okay, lets dig into this. We need to know what model year this Super Duty is AND is it equipped with electronic automatic climate control with push buttons or a manual climate control with dials?
2004 f350 XL manual everything, except transmission. PO ran it as an oil or logging rig and had some weird stuff on it. The extension cord was wired into the blower motor power and grounded to the battery! The wire harness as above. I replaced the manual climate control with a new dial as there was no power to the blower motor. That didn’t change anything. That’s what I know. I’m thinking there must be a break in wire somewhere but I’m not sure where to start looking.


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I haven’t test this relay, But after looking through this on alldata I guess it’s on the list of possibles.


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