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Let me start by saying that I have been Googling for similar situations for weeks, and for the life of me cannot find anything similar. Additionally, I would consider myself reasonably good at electrical diagnostics, and have eliminated as much as I can without replacing parts or digging into a wiring harness.

So, I've owned the truck for over a year, and never once have I had issues with blowing any fuses. About a month ago, truck wouldn't start, determined that the alternator wasn't charging, so I replaced the alternator. Went through 2 Napa alternators before going with a better company, and have had no issues since. About 3 days after replacing the alternator, I connect my 5th wheel, and we set out to go camping in the 90 degree weather. I realize just as we are pulling out, no A/C. After looking more into it, I could feel some cold air sitting in the vents, basically moving through convection, and it was actually the blower that stopped working. Also, no Tow/Haul function.

After determining that Fuse #24 under the dash, controls both the Blower and Tow/Haul, I checked in, and sure enough, fuse is blown. Replaced the fuse, and no issues the rest of the day.

The next day, at the camp site, with the trailer disconnected, fuse blows again. I get home, figure it must be the blower is pulling too much current, so I replace the blower motor, and the blower relay. No issues for two days, and then, fuse blows again. I pull the fan resistor, looks perfect. Just in case, I pull the plug on the resistor, and run the blower on high setting (only one that will work with the resistor disconnected), and the next day, the fuse blows again. Each time, I have no tow/haul feature. So, I disconnect the blower motor plug and wait for 3 days, fuse doesn't blow.

So, now I decide to plug the blower back in and just run the climate control in defrost, which still engages the A/C clutch, but hopefully narrows down the issue. A day later, fuse blows. So, now I know that its looking to be related to when the A/C is on. To confirm, I run the climate control in dash mode only, so no A/C function is turned on at all. Its been a week, no blown fuse.

So, I have thought about the shift lever issue where the harness shorts out, but the fuse never blows when I'm using the Tow/Haul function, only when using A/C.

Now I am thinking that maybe its an issue with the A/C compressor clutch coil pulling too much current, but that seems like a stretch. Especially because I think the A/C circuit has its own fuse that would blow if there were issues there.

I am pulling my hair out, but have no idea where else there could be a short. Sure it could be in a harness, but in my many years working on cars of all types, it is almost never within the harness (I've actually never experienced an issue within the harness, unless someone messed with it, or it was in an accident. Neither are the case here.

I'm really hoping that someone can show me a circuit diagram for the 2005 F350 blower motor, or if someone else has had a similar experience, or can offer insight that I may have missed.

Thanks in advance...
 

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Discussion Starter #2
Still experiencing the same issue... anyone have a diagram I could use to track the issue down? Now I am thinking the issue might be behind the dash, maybe a blend door/actuator, or the switch/controls....
 

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Very interesting, I have had the same thing with my 2005 F-250 Superduty 6.0 diesel 4WD XL 4 door. I have thought I had it repaired a dozen times but it blows fuse #24 after driving it for a while. I have replaced, the fan, the fan relay, the low pressure switch, the blower resistor, several questionable wires and connectors. The dual pressure switch may be the problem, what else is there? I hope you have found a solution. Don
 

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did you ever come up with a fix. I am having the same problem
Same problem as BVA for two years now. I have replaced the blower motor, the blower motor resistor, the A/C selector switch in the dash, and the blower switch in the dash. Took apart the wire loom in the dash, no broken, burnt, or exposed wires. Took out the fuse block under the dash, no broken, burnt, or exposed wires. I took it to an A/C mechanic, can't figure it out. I took it to my regular mechanic, can't figure it out. Anybody have any ideas on this?
 

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Still experiencing the same issue... anyone have a diagram I could use to track the issue down? Now I am thinking the issue might be behind the dash, maybe a blend door/actuator, or the switch/controls....
Same problem as BVA for two years now. I have replaced the blower motor, the blower motor resistor, the A/C selector switch in the dash, and the blower switch in the dash. Took apart the wire loom in the dash, no broken, burnt, or exposed wires. Took out the fuse block under the dash, no broken, burnt, or exposed wires. I took it to an A/C mechanic, can't figure it out. I took it to my regular mechanic, can't figure it out. Anybody have any ideas on this? Did you ever come up with a solution?
 
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