I noticed this morning when I was on the Highway I went to switch lanes and my cruise went off, I hit resume and it came back on. I switched lanes again and the same thing happened. When I hit my right turn signal my cruise disengages, and its just my right turn signal. Any thoughts

 

Without the '97 schematic in front of me, I'm shootin' from the hip, but here's my theory:

The turn signal power from the multifunction switch is back-feeding through the MFS and sending the signal down the same wire that feeds the brake input from te brake pedal position switch to the cruise control servo. The servo thinks you've tapped the brakes (when you haven't) and cancels it.

The two culprits that come to mind are the multifunction switch and the BPP switch. My money would be on the multifunction switch, but I can't say for sure.

Offhand, I can't tell you where to look. I'll have to check the schematics when I get back to work Monday unless someone else pops them up here over the weekend. Sorry.

-Joe

 

Just stared a tthe schematics for a few minutes.... The light green wire is connected from the BOO switch to just about everything. If the LG wire is getting powered when you flip on the right turn signal, it's back-feeding and that's what's killing the cruise.

Soooo.... The best way I can figure to test it is to isolate that circuit from the battery by pulling Fuse #13 (15A) from the Junction Box Fuse/Relay panel under the dash. Check witha 12V test light and you should have power on one terminal but not the other. Then, turn the key on and confirm that the LG wire is dead by tapping the brakes. You should have no brake lights and probably can't pull it out of park.

Now, flip the right turn signal on and check for any kind of voltage spike at the fuse box. You should still only have power on one of the two terminals, not both. I suspect that you're getting at least intermittent power to both of those terminals and that's what's killing the cruise. It may not be much as that wire ties into a ton of other items, but a digital multimeter should be able to pick something up if it's doing what i think it is.

The next thing to check would be up at the switch itself, but I'm not sure how you could isloate just the BOO input wire, unless you can de-pin the harness or clip the wire. If you can access the LG wire in the column near the multifunction switch, you may be able to get a better reading there. If you can clip that wire or de-pin the connector to completely isolate that wire from the system, that would be even better. Then you can check for voltage coming back through that switch with the turn signal on (and the fuse in, of course) without anything else being connected.

Thermo, does this sound good to you?

Good luck!

 

Check the front & rear turn/brake signals. You could have a shorted bulb.

 

I fail to see how a shorted bulb could cause the cruise control to turn off. Where's the turn signal bulb going to short to? The only two possibilities would be the parking light filament and back through one of the other bulbs' ground, or to the ground connection for that bulb. Either way, the current goes to ground right there at the bulb. If it shorted to ground, it would blow the turn signal fuse, and the turn signal would either not blink, or blink rapidly. He didn't mention either of those cases, and didn't say anything about a turn signal bulb being out, so I'm operating on the assumption that the signals are working properly.

-Joe

 

Remember what ASSUME will do to ya.

 

Indeed, but what else can you do on teh boards? Unless told otherwise, it's generally safe to assume that the symptoms as presented are what's happening... Unless, of course, they're not giving us the whole story. (Not that that ever happens though LOL!!)

 

Thanks for all the help this is why I love this forum, I would have wrote sooner, but this is my first chance at an internet connection. I havent had a chance to check the bulbs but Im assuming they are fine because they dont blink fast (maybe this is a wrong assumption) I did forget to mention that the night before this that when I went to hit the right turn signal and click it up that it would blink really fast. It was weird it only did it that night. I will check both turn signal bulbs tommorow, and see if the cruise disengages.

 

mine did it for the first time. ill keep an eye on it. i know where my problem will be. that damn spendy multifunction switch had a broken LG wire end into the harness. quite the pain to get to when you have no idea of the easiest way. quirks of mine: self soldered connection and i hate soldering, especially in tight areas so i may not of done a good job. i have noticed the signal does occasionally speed up. atleast once a week. i will take Joes observations of the schematic and toy with mine some if it ever acts up anymore.

my observation of the multifunc switch on my truck. the LG wire was routed SHORT and that means its tight, pulling on the wire. so after 8 years i guess of vibrations and slight movement. it decided to break behind factory solder.

 

Note the symptoms. The turn signals work, it is the cruise control that is turning off.

Like Joe said, a shorted bulb would blow a fuse if shorted to ground, elements grounded together would have the turn signal bulb illuminated like a parking lamp.

On to the problem....
On to a suggestion, is the turn signal action what is causing the CC to turn off, or is it the turning of the wheel ?

Next time try a Chicago lane change, just turn the wheel, and take all 3 lanes in one fell swoop and see if the CC shuts off.

 

When I originally switched lanes I thought it was the steering motion that had something to do with it, but it will do it going straight down the road, but goes off as soon as you hit the turn signal to the right.