CRUISE CONTROL WARNING

[Jon Wehrenberg]

Ed (Sawdust) asked me to relay this message because he is unable to get on the internet.

He had an incident today in which his cruise control would not disengage with application of his brakes.

I will not go into a technical discussion of the circuits since I have not looked to see what may have caused this, although Ed apparently has determined it is a relay relating to the ABS. What is important is that you all know your cruise control may not disengage when you apply your brakes.

When you are on cruise, and you apply your brakes, the red brake annunciator light on the dash lights and simultaneouls with that the cruise control disengages. Today Ed had to make a rapid stop and his cruise control did not disengage, nor did the red light on the dash light.

In his case he was unable to stop where he needed to, but fortunately nothing bad happened as a result.

He did indicate that at around 35 miles an hour his cruise did disengage.

I would urge all to be aware that the cruise control circuit like all mechanical things can have failures. This is a case where a failure can have dire consequences. I have experienced a similar event in the past, and ever since then have never relied on my braking to disengage my cruise. I would urge all others to manually disengage the cruise control any time traffic is heavy, any time a stop is anticipated such as when coming to a rest area, or an exit ramp, or when on curvy narrow roads where visibility is limited.

The cruise control can be disengaged using the brake, the square white button, or the cruise control switch. Ed will post more details and I will attempt to verify which likely component failure can cause this problem, but regardless of what causes it, you as a driver should be prepared to manually disengage your cruise control as your primary means rather than relying on braking to do it for you.

At the very least please recognize if the red brake annunciator does not light when the brakes are applied and the cruise is engaged, it means the cruise has likely not disengaged and you may not be able to stop as planned. While you are applying maximum braking effort, your cruise control is applying maximum horsepower in an attempt to maintain the set speed.

[HarborBus]

That's pretty scary, thanks for the heads up and we'll look forward to Ed's update and possible preventive measures that can be taken..

[phorner]

Good info to have. Glad to hear that there was no serious outcome to this episode.

Would hitting the "Decel" button resolve this problem?

[GDeen]

Seems like this has been discussed as a problem before??

[flyu2there]

http://www.boston.com/video/viral_pa...id=17735942001


Jon,

The above link is some training underway in a bus simulator. I really don't know if there are any available to the public at large but I certainly see a benefit. The airlines have used them for years, they also used for ships and other large equipment. Emergencies of all kinds can be demonstrated and practiced.......... While simulators cannot prepare one for every eventuality things like front tire blow outs at 75 mph certainly can demonstrated and trained.

I have no idea what actually happened to Sawdust, however we should all learn from this incident. A little initial or recurrent training, at least in the mind, really is a requirement. Personally I have attached little stick on goodies to both my jake brake and my cruise control...one has one bump, the other has two. The logic behind that is that I do not have to look at the switches, I have learned them by feel. I recently read of a gentleman who had a stuck wide open throttle on his car, he did nothing and ran into someone else causing serious injury. Did it ever enter his mind to put the car into neutral....no it did not. Turning off the ignition would also have been an alternative, just enough to stop the engine then back on to avoid the steering column lock up....instead he drove right into the car in front of him.

While the mechanical aspect of what went wrong is very important, I feel it equally important to review what we would do in the same situation.

[Jon Wehrenberg]

I'm glad to see John's post because as a pilot we do train for unanticipated events such as failures of controls or devices that require quick and correct intervention.

When my cruise did not disengage with brake application many moons ago, I had no immediate pressure to get the coach stopped, so the brain fart we all experience when faced with an unexpected problem that requires attention NOW did not occur. I was able to play to see if the brakes would disengage the cruise (they would not), and then I tried the white button (it would not), so I just turned off the switch which did disengage the cruise.

The next time I used the cruise it worked fine, but from that experience I developed the habit of never expecting the brake to disengage the cruise. My practice now is to disengage it with the white button ahead of when I anticipate slowing or stopping and I never use it when I can anticipate I will have to slow down frequently. That might explain in part my 62.5 MPH speeds.

I have found some side benefits to operating the cruise as I do. John mentions being able to identify switches by touch. Since I am always using the white button or the rocker switches to control the cruise I no longer have to even look down. My hand goes to the exact button I intend to operate and there is no conscious thought involved. That's a good thing because I can react correctly without thinking and being delayed by the brain fart. (Trust me, at the first signs of an abnormal situation that requires your immediate attention your brain goes blank while it tries to process what is happening. That is why John's mention of training is so critical.)

Perhaps today we can identify and verify the cause. That is a secondary consideration because when you need to stop and the cruise does not disengage you will not be thinking about changing relays. You will be looking at the car ahead or the stop sign getting very close very fast.

[Larry W]

I think that if touching the brakes does not cancel the cruise the white button won't cancel the cruise. I have not looked at he wiring diagrams yet, but when the white button is pushed the red light on the dash comes on just like it does when the brakes are applied. I think most of you have the right answer to cancelling the cruise. Turn it off. I guess if that does not work turning of the key would be the last resort.

[Coloradobus]

Larry,

I would be suspect of your brake switch which a round silver part with 2 wires attached under the driver's seat in the lower compartment. It has a 4 psi air pressure useage where it is screwed into place. The cruise disconnect is tied into the brake light engagement. Check to see if you have brake lights when this happens. Do your brake light indicator light on the dash light? If it doesn't, that's you culprit. They are 38 dollars at Prevost. The H3-45's have 2. Also if your brake lights stick 'ON" after hitting the brake pedal, especially in cooler weather, its the brake light switch sticking.
We had same problem bringing the Beaver home. Cruise would not disengage, no brake lights with foot pedal. Replacement of the switch, all is well.

[tdelorme]

I'm glad to get this info before it happened to me. Of course being the cool headed dude that I am I'm sure it would have not been an issue. Cleaning up the seat might have been a problem for Jan though, so it's good to know.
My father in law was with me one day when a dog ran out in front of us. I did nothing but get the standard death grip on the wheel as I hit the animal. He gave me an interesting talk on how to avoid becoming "object struck" in those kind of situations. The main thing I remember him saying was to be aware that action was needed and not to freeze, do something effective. He was an old Marine Pilot whose pilot's license was signed by Orval Wright.

[LA-HODAG]

I had the same experience as Coloradobus after having some service done. Connector from the switch to the brake light circuit had gotten disconnected. No brake lights, no cruise cancellation. And pressing the square white button did not work to cancel either. I had to turn off the main cruise control switch. It's scary when stuff like that happens. Now I always test the disengage function at the start of a trip.