How to fix your subwoofer amplifier 7L2T-18C808-AA
The OEM subwoofer amp p/n 7L2T-18C808-AA is used on a number of Ford models including the F150, Mark LT, and Edge. Eventually a lot of these units fail when the subwoofer starts cutting out randomly while driving. Turning the head unit off and on again can restore the signal temporarily, until the speaker cuts out again. After the usual searching it seemed the fix was to buy a new amp from Ford to the tune of $100. I decided to try to fix the old amp before forking over the cash.
I suspected the problem was a bad solder joint on the circuit board. Usually it's the larger high-current and/or mechanical load-bearing solder joints that fail, so I resoldered all those joints first, with no improvement. So, with the amp apart and plugged into the harness and playing music, I started smacking every component with the back of a small screwdriver until I found the one that killed the amp every time. Turned out it was one of the small capacitors near the speaker output connector. Touching up those solder joints fixed the problem. It's been about a week now with no cut-outs so I feel pretty good that it's fixed once & for all.
Pics show the problem areas. If you have basic soldering skills, this is a pretty simple fix. Hope this helps someone.