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My first suspect is a bad ground. The ground for the brake lights and signals is common. Additionally, the Cruise Control will turn off if power is lost, so I feel that is the first thing needing checked. A weak ground may work for one thing, but when additional load is added, it can fail.
I attached two pictures. The first shows the common ground I referred to. I circled it in the picture. The second shows splices to ground, so make sure they are good too.
Check the wiring to the body mount as indicated. Confirm it is tight, clean, and not damaged in any way. Move it around to confirm nothing is broken.
Here are a few links you may find helpful when checking electrical issues:
Start with this and let me know the results.
Images (Click to enlarge)
Wednesday, May 29th, 2019 AT 6:51 PM