Was I fed a load of crap--------pie by this dealer??????????

[LBM]

The cruise control on my F-150 has quit working on my last outing while pulling the boat. I took the truck into the dealer and after they checked it they said it worked fine. After further explaining how it didn’t work for me they said that a bad trailer light would cause the cruise control to not work.

Not being someone of quick wit and with more thought on this subject and after paying the dealer $55 for their evaluation I have great doubts about this statement.

I currently have LED tail lights on my boat trailer and in the past with bulb type tail lights I don’t recall my cruise not working when a trailer tail light had burnt out.

I just can’t believe that Ford would design the cruise control to work in this manner when I have always felt like auto companies would pay design engineers bonuses when ever they designed something that would thwart a shad tree mechanics or force them to have to buy a special tool to work on a vehicle.

With the diverse group of Crappie comers members I was hoping someone might be able to explain to me just how a bad trailer light will cause the cruise control to not work.

My simpleton evaluation of the situation would be a bad set switch on the cruise control. When it doesn’t work the cruise light on the dash will come on when I push the set switch but won’t stay on and of course the speed won’t hold.

I’m hoping someone here might be able to clue in a clueless one.

[CatFan]

Does it only act up when the trailer is connected?

[LBM]

Yes. The trailer wasn't hooked to the truck when I left it with the dealer. When I drove it home yesterday it seemed to work at a 35 mph at a speed I don't normally use my cruise.

[CatFan]

I think they are right to some degree. The resistance of the LED to ground can mess with the sensor detecting the brake lights.

What year is the truck?

[Wannabe...]

Sounds like poo to me. I don't see how or why there would be any input to the ECU from the tail lights or trailer wiring harness. One thought though, and this makes no sense, is the cruise is cancelled when you hit the brake lights. I guess it's possible there is some sensor to keep the cruise from setting if the tail lights - ie trailer lights don't work. Doesn't make sense though as it's much easier (cheaper) to wire into the foot pedal. If the trailer light turns out the be the problem, that Ford engineer should be drawn, quartered and forced to work the at the drive through at McDonalds on the 11 to 7 overnight shift for at least 4 years.

Wannabe...

[siscoken]

I am a GM mechanic and so I cannot speak for Ford, but I know that on some GM,s if the body control module detects a problem in the rear lighting system that it will disable the cruise. You may have to isolate your trailer wiring with a module.
So to answer your question, a rear lighting system drawing more current than the module expects to see could very well disable your cruise.
Hope this helps Ken

[CatFan]

Sounds like poo to me. I don't see how or why there would be any input to the ECU from the tail lights or trailer wiring harness. One thought though, and this makes no sense, is the cruise is cancelled when you hit the brake lights.

Some of them work just the opposite of how you'd think. They sense ground through the low resistance of the bulb, and when the light is on, there is no ground. I assume this is done so the dash indicators for bad bulbs can work. LEDs don't have that low resistance path to ground, so they look like blown bulbs to the cruise.

[Locator79]

There was a recall last summer for F-150 cruise controls. Took mine to the dealer, 5 min fix, but cant remeber what the problem was.

[LBM]

Catfan it is a 2001.

Locator79 I had that same recall a year or so only the dealer didn't have the part then and they disabled the cruise and I had to wait over a month before they got the part in. Guess I was low on their list of who to take care of first.

[h2omaker23]

I had a ford sport trac that did the same thing a couple of years ago. The cruise eventually started making a buzzing noise at times and they replaced it. Never had any other troubles.