eGuru

There are no external signals that affect the rear view mirror dimming functions. What year/model did the replacement come from - pinouts may be different.

Look for a tilt switch near the firewall on the driver's side. Does the rear dome light come on when you open a door or is it burned out?

What else? I assume you replaced the airbag (with a new one? from a recycler?). What is the symptom - error message? Are you expecting to find a physical "reset" switch?

You haven't told us make/model/year of your vehicle.

After you find it, what are you planning to do with it? What symptom are you trying to correct? Did you have a collision that caused the airbag to deploy?

Hi FXT. Are all these symptoms being reported by ForScan or are you making measurements with a DMM? Have you examined the connections/wires at the rack for corrosion damage - especially since you mention that the problem first surfaced during wet driving conditions. There are many pin-point tests that can be performed using only a DMM but they would require significant amount of effort on your part. Unfortunately I am in the middle of moving to a new house and don't have access to the documentation to perform the tests at this time. It will probably be a week before I will be able to dig them out. In the mean time, keep us updated and good luck.

There is no separate fuse for the indicators. Sounds like the instrument cluster is defective. You can get a replacement at a recycler, eBay, etc but you will need to have a dealer perform the installation as programming is required.

Replace the ETB and definitely stop using the seafoam.

I am not understanding your post. Are you saying that cooling is fine but heating is sometimes insufficient? Is the air flow consistent?

If you haven't installed the CAI you can probably sell it at a better price and save yourself the labour. These CAI's are no better than stock and in some ways worse.

What are the symptoms of your failed steering system - failure codes, etc. Absolutely, a failing 12V battery will cause all kinds of issues. 10.x volts is definitely a bad value. If the battery is over 3 years old - just replace it. Don't bother to have it "tested". If your battery is newer, invest in a DMM to get a proper voltage measurement and help with this and future diagnosis.

Who is telling you that an alternator can be rewound to produce more current? The rectifiers would need to be replaced and would need improved heat sinking - something that the existing shell can't accommodate. The PCM software needs to be matched to the installed options.

If the connector or wiring has been damaged then a new rack wouldn't solve the issue.

If the ebay picture is similar to yours and it says it is for 2010-2012 Fusion in the ad, then it should be fine.

This is not the best video but you will see how to access the switch. Buy yourself some plastic panel removal prying tools. You can get a set for about $10. Don't use a screw driver. https://www.youtube.com/watch?v=60gXAz3gDJE&ab_channel=Nickthecarguy

You are only half right sir. You are wrong about my profession - I am not a mechanic. But you are correct that I was not so bright when I tried to help you. Clearly you are much more highly educated than myself or the average forum member. Strange that you would take the time to observe the turn-off time so many times that you could determine a mean (x-bar) of the fan turn-off time to 2 decimal places but can't be bothered to open the hood when your sound issue occurs to check if your sound issue might be due to the fan. Please tell us how you were able to determine "no fan keeps turning 4 minutes of the car being turned off." because I am curious how a defective fan speed controller or CHT sensor couldn't possibly cause the fan to startup again after the engine has been turned off. Awaiting some enlightenment sir.

If the new blend door actuator did not move when plugged into the harness (but not physically attached), then you can suspect that the HVAC controller or the wiring is the cause. Meter the resistance to ground, at the connector, of the wire that connects to the center pot pin. If you have recently had your passenger air bag replaced, that wire may have been broken in the process.

If you weren't observing the fan, how are you eliminating it is a cause of the noise?

You need to be able access the connections on the mirror control switch to diagnose your problem. Do you have a digital multimeter?

Were you observing the fan or just assuming it should have been stopped?

Measure the voltage on the center pot pin (with respect to ground) at the travel extremes and while the actuator motor is moving. You should see roughly 0.5V to 4.5V. btw - driving the actuator motor to its travel limits using a battery can wreck the pot. It's okay to do it while the actuator is still mechanically coupled to the damper because it can't over travel . If it is mechanically uncoupled it can over travel. So if you are in the process of installing the new actuator, don't "test" it before coupling it up.

By "whirling sound", I assume you mean it sounds like fan. Perhaps it is the ICE cooling fan.

I with @akirby and @bbf2530 that you need to pull the codes that are causing your CEL before replacing any more parts. The fouled plug points to a mechanical issue and not electrical but either way, you need to qualified mechanic with the proper diagnostic equipment to analyze the cause.

Have you been monitoring your oil usage and coolant levels?

Please post a picture of a "blown" plug. That could help us narrow down the cause. Which engine do you have? mileage?