I have a 03 FLHTC. 130,000 miles. I put cruise control on it at about 30,000 miles. Have had problems off and on. Much more time all is well, but everso often, when the cruise is activated the green light on the tach will not come on and of course the cruise is not engaged. I always thought it was the switch in the  hand controls. I would shoot it with some electrical spray and all would be fine. Now it doesn't work (the spray). So I changed the switch in the controls still intermittent. Been talking a little bit and reading the manual, found out there is a test for the switch and it is ok. Much work for not. Sounds like it is probably the idle cable. I just found out after reading the manual that there is a roll off switch in the idle cable. Mine has never worked. I always thought it was kind of dumb the only way to deactivate the cruise was to hit the break. Most of the tests check out ok. Anybody with any ideas! I use my bike daily and  pull a trailer behind it daily in my business. I use the cruise a lot and what a pain in the ass when it doesn't work
Thanks Tim007