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Wayne Crawford
Wayne Crawford, Shop Owner
Category: Ford
Satisfied Customers: 3904
Experience:  General Repair Shop Owner
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I keep blowing fuse #33 (under the Hood Fuse Box) when I put

Customer Question

I keep blowing fuse #33 (under the Hood Fuse Box) when I put it in reverse.
Submitted: 1 year ago.
Category: Ford
Expert:  Wayne Crawford replied 1 year ago.

Hello. My name is ***** ***** I will be helping you today.

Have you removed all the rear bulbs and checked both the bulbs and sockets for melting or corroding issues?

Customer: replied 1 year ago.
I've even removed all the bulbs and all the sockets and the fuse still blows. No melting, no corrosion. The driver’s side socket looks a little 'Dark' around where the bulb plugs in, but so did my 2002 Excusions (which didn't have any issues). Here is my understanding of the Gray/Orange wires. (Maybe I'm wrong, if so please correct me). There are two (2) identical Gray/Orange wires in the Main Wiring Harness coming from the front of the truck. These are the reversing lamp wires. They supply power to the 1) Trailer plug and the Taillight Harness with the wire going to the driver’s side brake light socket. Important Note: The Taillight Harness wire from the Main Wiring Harness goes straight to the Trailer plug. The Taillight Harness wire from the Main Wiring Harness goes to a plug that plugs into the Taillight Harness.
Here are my tests:
1) I unplugged the rear Taillight Harness 'socket/plug', and connected the Trailer Harness Gray/Orange wire from the Main Wiring Harness directly to the Gray/Orange wire in the Taillight Harness. Well the Backup light works, and reversing sensor beeps (did not work at all before) no fuse blown. SO I'm thinking that the Taillight Harness Gray/Orange wire must be bad somewhere in the Main Harness and I'll just connect the Taillight Harness Main Harness wire to BOTH the Taillight Harness plug and the Trailer Harness. Fuse blows.
2) I figure let me get my reverse lights working (Main reason I went down this road) and the reverse sensor so I'll just use the Trailer wire from the Main Wiring Harness, remove the 'Pin" from the Taillight Harness Plug/Socket and put the Trailer Harness wire in the Plug/Socket instead. I'll worry about the Trailer another time. As soon as the Taillight Harness in plugged into the Main Wiring Harness, Fuse blows. So I figure it must be in the Taillight Harness, which I just ordered for $50.
It would be much easier for me to explain over the phone(###) ###-####
Expert:  Wayne Crawford replied 1 year ago.

With what you have done and the results that sounds right. It doesnt blow till you plug in the taillight harness so it pretty much has to be in the taillight harness.

Phone calls are an additional service at an additional cost. I cant call without it. I submitted an additonal service offer. If you accept it let me know when you want a call.

It really doesnt seem like you need it. I think your issue is resolved at this point.

Customer: replied 1 year ago.
Installed New Taillight harness 8C3Z-13A409A. No Bulbs, no sockets plugged in. When I plugged in the New Taillight Harness it Still blows fuse #33 when put in reverse.
Expert:  Wayne Crawford replied 1 year ago.

And it doesnt blow it with the harness unplugged?

Customer: replied 1 year ago.
Correct. If the Taillight harness is unplugged, the fuse does not blow. If I Unplug the Taillight Harness and 'bypass' the harness by connecting one of the gray/orange wires directly to the Taillight harness (which is completely unplugged) the reverse lights work and the backup sensor beeps. I bypass the Taillight harness by removing a small amount of insulation and connecting a 'alligator' clip to the gray/orange wire coming from the Main Wiring Harness.
Expert:  Wayne Crawford replied 1 year ago.

Have you tried unplugging the trailer harness? Same results?

Customer: replied 1 year ago.
There is no Trailer Harness right now. I cut it off. Let me explain: I bought this truck last July. After owning it for a couple of months I noticed that I did not have any reverse lights. Checked fuses, etc, etc. When I got back to the rear of the truck I noticed another harness had been 'Hacked' into the Main Wiring Harness very near the Trailer Plug. Somebody before me had the truck rigged for a Fifth Wheel Trailer and put a plug into the Drivers Side bed. It could not be seen because of the Bedliner. So the first thing I did was buy a New Trailer Harness (48" long) that goes from the Main Wiring Harness to the back of the Trailer Module that is mounted to the Trailer Hitch. I also bought a new The Module that you plug the Trailers actual plug into (either 7 pin of 4 pin). Cut off the old Trailer plug that plugs into the 'Back' of that Module. and removed the Harness going up to the bed. So all I have is 7 or 8 wires that are cut off that go to the New Trailer Plug (that plugs into the back of the Module). They are not connected to anything. Could the Main Wiring Harness be looking for these to be connected to the Triler Plug that goes into the back of the Module?
Expert:  Wayne Crawford replied 1 year ago.

No.. even if it was it wouldnt blow a fuse. With everything plugged in check continuity at the bulb sockets for any to be shorted to ground.

Customer: replied 1 year ago.
I have a multimeter, but how do I check for the short you describe?
Expert:  Wayne Crawford replied 1 year ago.

Touch your red lead to the positive terminal and your black lead to the negative terminal with the meter set to ohms (1k or audible). No positive terminal should show anything under like 100 Ohms to the ground.

Customer: replied 1 year ago.
I forgot to add, during one of my many tests, I noticed that when I got the reverse lights to work, the Drivers Brake light would 'softly glow'. I then noticed that the Drivers Brake Light has that same gray/orange wire going into it.....
Expert:  Wayne Crawford replied 1 year ago.

Thats an indication of a short. Unplug the drivers brake light socket from the harness and recheck everything.

Customer: replied 1 year ago.
Okay here is what I found. Multimeter set to k(ohms). I put the Black probe to the Black/White wire pin and the Red probe to the Gray/Orange pin. I got a 00.2 reading. I then tried the passenger side and got the same with the Black/White and Purple/Red wires.
I noticed that this new Harness has changes the Gray/Orange wire in the Taillight harness to Gray/Brown or Purple. Is it normal for them to change colors like that?
OLD Drivers plug had Black/White then Purple/White then Gray/Orange
NEW Drivers plug has Black/White then Purple/White then Gray/Brown or Purple
OLD Passenger plug had Black/White then Purple/White then Purple/Red
NEW Passenger plug had Black/White then Purple/White then Purple/Red
Customer: replied 1 year ago.
I have to go to work. Talk to you later today.
Expert:  Wayne Crawford replied 1 year ago.

Try unplugging the parking aid module. I am attaching the R&R instructions to aid you in finding it.

Customer: replied 1 year ago.
I don't see any attached files....where do I look?
Expert:  Wayne Crawford replied 1 year ago.

Im not sure what happened. Trying again here.