Back in December our 2015 MKC with THX started developing issues with the stereo. Muffled tinny sound that would only come out of a couple of the speakers. It was intermittent at first, but after a few weeks it rarely worked for more than a few minutes here and there. Lately, I would get random static out of the speakers even if the stereo was totally off. I got some time today to take a closer look.
I can confirm the amplifier is in the back by the spare tire. Three wiring harnesses to unplug and it comes right out. It's not even screwed to the chassis. I noticed that when I jiggled one of the harnesses I would get a lot of static, so I tried the suggestions that Buckeye posted. I used a T10 screwdriver and took out 12 screws around the case. With the case off, it looked like it was mostly in good shape. I was hoping to see a bulging capacitor or a broken solder joint, but no such luck.
The only issue I could visibly see is some of the copper on the back of the circuit board that contacted the case had been scratched off. I cleaned up the case with a file, and cleaned the copper areas with a pencil eraser. I took some flux paste and tried to get some solder to cover the scratches. I then proceeded to add a little solder to every major solder joint on the board, paying specific attention to the harness connector that was the source of the static. I put the case back on, and plugged it back in.
It worked! At least it did, initially. There was no more static when I jiggled the harness, that is fixed for sure. The stereo sounded good for a few minutes. I don't think sound was coming from all the speakers, but some is better than none. I felt like I accomplished something for the day.
Then I came back to the car a few hours later. Still worked, but as I messed around with the sound settings some more, I decided to try the THX demo, and then the whole thing went kaput. Back to the muffled sound, maybe worse than before. Well that sure took the wind out of my sails. So my amateur hour micro-electronics skills weren't enough to fix it I'm afraid. I just unplugged the amplifier for now.
Maybe I'll give it another go at some point, but I don't think we'll have the MKC much longer. I don't want to spend 350 for a new amp + 100-150 for Ford/Lincoln to perform their mysterious programming that's needed to work correctly if I'm trading it in the spring. Also, the model numbers for this amp are very confusing. It seems like they have changed it several times. Maybe that's why the programming is needed? Who knows.