Corroded Engine Harness

[Drewas]

Hello all Mustang lovers,

I am dealing with a reoccurring issue on my 2015 V6 Mustang, and it is a series of events so bare with me. Last winter my battery had expanded and leaked battery acid everywhere due to extreme cold temperatures. One morning I went to start my car and the entire car had zero power (Doors weren't even functional). I popped the hood to discover a huge battery acid mess, so I took some hot water and baking soda and cleaned it all up and the car started right up. A month later a similar issue occurred when I went to start it, the battery acid had come back with a vengeance and completely ate away at the terminals making them useless. So I cut the factory terminals and replaced them with a brand new set and coated them with anti corrosion spray, along with a brand new battery. A month later, I went to start my car one morning and the whole car went black again. This time, the corrosion had spread down the engine harness and was visible on this grounded wire located by the passenger side strut, so I used a wire brush to clean it up and the car started right up! It ran for a few months this time until the other day they same thing happened, I went to start it and the whole car went black as soon as I touched the ignition.

I thoroughly looked at all the end points on the engine harness and could not see any visible corrosion, but just to make sure I sprayed corrosion eliminator on every end point (stater, starter solenoid, alternator, etc.). Unfortunately this did not help, and at this point not even jumping the battery allowed the car to hold any sort of power. A friend of mine mentioned that it sounded like there might be a short or parasitic draw from something, and I immediately thought of my LED lights that I installed in my floorboards, and OEM door panels. I reverse engineered the LED lights and as soon as I disconnected them, the car was able to hold power but still would not turn the engine over. I grabbed another vehicle and tried to jump it and it started right up, but after I drove the car around the block I turned it off and the car went black. This is where I currently stand. I tried jumping it and this is what is happening. I managed to get it started once off dumb luck and gave it a few revs once the engine was up to temp, and every single light started flashing all at once and I smelled burning electronics so I shut it off. This has been extremely frustrating and I have run out of ideas so PLEASE someone help!

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[Smunczen]

I’d say the acid wicked in to the wires. I would
Think you might have to replace the effected wiring harness it self.

 

[boB]

I’d say the acid wicked in to the wires. I would
Think you might have to replace the effected wiring harness it self.

Yep. Patching up the harness is likely to cause you ongoing trouble.
And crimp-on connectors/terminals have no sealing, proper terminals are solder-dipped to seal the connection *and* the wire strands to prevent moisture from wicking.

 

[ice445]

Yep. Patching up the harness is likely to cause you ongoing trouble.
And crimp-on connectors/terminals have no sealing, proper terminals are solder-dipped to seal the connection *and* the wire strands to prevent moisture from wicking.

Most of the decent ones have silicone grease inside the heatshrink that melts and seals it up once you put heat to it. With that said, I see cheap wire taps here and all sorts of nonsense.

I feel bad for OP because stuff like this is an absolute nightmare on modern cars.

 

[Cobra Jet]

I am going to guess that the "aftermarket" added battery terminals are the issue. These newer modern cars are tied into multiple BCM's and CANbus wiring where even the slightest difference in wiring resistance (amps, volts, ohms, etc.) can cause many issues.

If battery acid was to corrode the end of a wire (any wire) it's not going to wick up another 6" or even 5ft+ of wire. It also won't "jump" from one harness to the next as you're pointing to in the 1st image.

Corrosion can be caused by many things including atmosphere, geographic location, if car was flooded at some point, or just sitting moisture collected from the air.

Corrosion as you're pointing out in the 1st image in the ground terminal can be either moisture related OR having 2 dissimilar metals in contact with each other.

If you were to snip off the end of that ground cable 2"-4" up, the inner wire after the corrosion should be "like new". I'm not telling you to do that, I'm just saying and using it as an example.

If you have installed anything aftermarket that is hooked into the vehicle's wiring or grounds - disconnect completely and see if there's any difference with starting the car or battery draw.

You can also remove ground wires under the hood, clean the mating surface (where they are attached) and also clean the terminal itself at the cable. Emory paper or even a small wire brush will clean the surfaces and terminals. Make sure there's always good grounds.

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