Topic diversion: My neighbors Fiesta (Ford)

2011 Fiesta. The entire fuse panel under the hood had corroded so much that 70% of the fuses had the tabs corroded off of them. At my suggestion he purchased a good used fuse panel. It has 27 fuses, and ~14 relays in it. The seller of the good replacement cut the box out of a wreck with a demo saw. Chopping close to the box! We have had a recreational time splicing wires. When the battery was installed, the left headlight came on. Disconnecting the right headlight caused it to shut off!. A very long story cut short. Of the 50 plus splices, there was a major discovery tonight. Ford in its wisdom used a brown with blue trace wire from the fuse for the right hand low beam. It also used a brown with blue wire of the same size in the same bundle from the chassis control module low beam control circuit. My neighbor had exactly a 50/50 chance of getting it right. Nope. I surmised that if the module was being grounded through the headlight filament, it would signal the chassis control module to send a lights on signal to the low beam relay. (there was much testing, and two Flukes involved. the headlight wire showed 12v when disconnected, and .1 volts when connected to the filament. this lead me to believe it was signal level, not power level. (the wiring book is 140 pages) We disconnected both brown blue wires and used aligator jumpers to rewire them the other 50% direction. And it got fixed!!! Woof. Jim

They circled the problem

You were lucky that was the only miswire in a project like that!

How the heck does a fusebox on a ten year-old car get to that state? There must be an interesting story behind that. I know of a disastrous surf fishing trip that had a similar outcome.

Ford is bad to change their parts midstream. It may have been the fuse box wasn't quite the right model. What did you do to prevent the fuse box from corroding again?

That's a good reason to stay away from flood cars. I seriously doubt you will ever see the end of electrical problems on it.

The question now, what next?

How many more corroded harness connections and modules are hiding under the dash and unknown places?

Neighbor needs a for sale sign! ASAP!

I've heard guys in the building trades say if you use the 50/50 rule you'll be wrong 75% of the time.

Likely more. Selling with as is notation will happen. I think the cover on the box is to blame as it could allow splashed salt from Minnesota roads to get in. Intent is to seal it better. The car is generally in great shape, The electrical system is over engineered and complex beyond reason. Jim

Yep...

Wiring a three phase motor, 50-50 chance it will run the right direction.

Very rarely happens.

Get the cover to seal good and then rework the vent so water, salt can not enter. Common problem on 2011 due to inadequate design. 2012 was improved according to internet.

A 3phase rotation indicator is available. Very few motors are made in opposition to the NEMA guidelines. Mine came in a Kit with 4 other testers including outlet polarity, voltage, ground fault identification, and signal tracer. Jim
example

When Freightliner built the first M2 trucks in early 2000s, they had a bulkhead module, located on the firewall, and a chassis module, located inside the left frame rail. The chassis module would get corrosion in one of its plugs quite frequently. The later models relocated it up under the cab, a little better protected. One module ran the left headlight and the other module ran the right headlamp. There several different problems that could happen: truck parked overnight and one head light came on by it self; only one headlamp would work; the box lights would either come on overnight by themselves or would not work. Was very interesting learning curve for a while! Mark.

I go by the 50-50-90 rule. If I have a 50-50 chance of doing something right 90 percent of the time Ill be wrong.

Yep, if it turns the right way the millwright buys coffee, wrong way the electrician buys.