I have a turn signal related problem. Symptoms; brake applied + left turn signal applied = instrument panel arrow on but no flashing action/sound (freeze). This can happen the other way around with turn signal applied first. Also another situation sometimes; cruise control on + left turn signal applied = cruise control turning off abruptly. These are intermittent events. I have reviewed the electrical schematics found in my 5 volume service manual, and can not find were brake, left turn signal and cruise control have proximity to each other. I have replaced brake and left turn bulbs, and checked a few connections with no effect. I almost decided to buy a turn signal/hazard/cruise switch and replace it, but noticed in the manual removal of other things like steering wheel, SIR disarm, etc. were involved which gave me pause when it looked like only upper and lower trim cowlings needed to be removed, switch fastened and connections made to install this switch.
This vehicle is a GMC Sierra 3500 pickup with crew cab/long box, 6.6 diesel.
In your answer you did not address the cruise control problem involvement (see question again). Does the cruise circuit also route through the Turn signal Flasher Module?
So, just pull module out and put another in with key off. No other considerations?