For quite a while I had a strange problem with my cruise control on my 96 F150 XLT. If I turned on my left turn signal to change lanes on the highway, my cruise control would cancel. No big deal, just hit resume and it would re-engage again right away. It wouldn't do that with the right turn signal, just the left. I had just changed my turn signal controls, so I thought there was just something weird going on with the controls.

Then I noticed that my right tail light was out. I pulled off the cover and the bulb was actually shattered. I changed the bulb and now the cruise control doesn't cancel when hitting the left turn signal.

Nothing real crucial here, but I'd be interested in hearing if anyone has an explanation for this.

 

Gremlins.

 

noticed this when I put LED bulbs in for the taillights on my truck. If I hit the brakes or turned either way, it would cancel the cruise, and the transmission would shift hard and would act really weird. It doesn't make sense to me lol. I even put load resistors on as recommended by the LED company to see if that would fix it, but it did not. I'm not sure really why the tails/turns are somehow linked to the cruise and the tranny, so I'd also like an explanation on this lol.

 

As far as the tranny, the speedometer (PSOM) which is a mini computer gathers info from the VSS, RABS module, and cruise control and sends a signal to the main computer which then (based on temp, throttle position etc.) decides what signal to send to the tranny. So if something messes with the cruise, I could see that messing with the tranny.
No idea why or how a bulb could mess with the cruise though.

 

If you hit brakes cc is supposed to cancel

 

When you signal left it grounds through right brake lite if that circuit is broken then the cruise thinks you touched the brake.

 

Nothing like a electrical problem ! I hope you got it fixed !