Cruise control problems

[nrhareiner]

Good afternoon everyone,

I have a very perplexing problem with my coach. It is an intermittent problem. At times my cruise control will disengage itself. At the same time the Jake brake will still work; however, the tell tale light for the brakes will not work if Jake used, and the small red light on control switch for Jake will not light when Jake is on. After awhile I will try and reengage the cruise, it will work and the Jake lights also work normally. Then after a period of time, and this is variable, the same thing happens all over again.

I thought it was probably one of the relays in the front run bay, so I changes these out. No change in symptoms.

The coach is a 2000 Prevost shell with DDEC II engine. Conversion is 02 Vantare S2

Any ideas?

Thank you

[JIM CHALOUPKA]

Kim, try to find any ground connections for the involved circuit, and or components, and check them for tightness and complete circuits.

You may also have a semi-faulty brake light switch. (dirty contacts)

Maybe the brake switch needs adjusting. (that is it is too sensitive to pedal movement)

I made this up, but what the hay no one else is around today:D:cool:

[Jon Wehrenberg]

Kim,

I think the cruise and Jake is tied in with DDEC. On the Prevost site you can access the wiring diagrams for your coach, including the connections to DDEC. If I were to guess it is not a fault in the brains, but a connection somewhere.

If I get a chance I will try to follow the circuitry and look for probable causes of what you describe. I assume you have left the relay that controls brake lights when the Jake is applied. Some of us have removed that relay. #76 I think in the rear box. BTW, that relay has no affect on cruise.

[nrhareiner]

Hello Jon and Jim,

Yes I have kept that relay in place. I was wondering if that relay could be causing the problems since I have replaced both the 12 and 24 volt relays in the front run box with no change.

Jim, I have thought about the possibility of a ground problem, but cannot find the common ground point that would influence both functions.

Kim

[Jon Wehrenberg]

Kim,

To the best of my knowledge that relay has no impact on anything but the lighting of the brake lights when the Jake or retarder engages.

Unlike the brake light circuit which is controlled by a pressure switch in the brake treadle air circuit which will disengage the cruise control, this relay operates the brake lights without disengaging the cruise. The intent is to show cars behind you that you are slowing down when the Jake or retarder engages, however as a practical matter both will engage even if just to maintain a given speed, and the constant application of brake lights when the Jake or retarder is engaged is annoying and confusing to drivers following you.

I will look around at the circuitry to see if there is anything obvious.

[Jon Wehrenberg]

Kim, I just went to some typical Prevost electrical diagrams and settled on D060938 pages 5.1 and 5.2. These are not for your coach but are close enough for this discussion. I could not find any one area to look for the problem due to my total lack of familiarity with the cruise control system.

I did see a lot of the coach systems are a part of the cruise control, such as the Jake, the brake lights, and the Pro Driver. All of that is integrated through the DDEC so I suggest that is the first place to look. Obviously the problem could lie with any of the hundreds of connections that are a part of the entire system related to the cruise control so your problem appears to be one for the experts.

[rickdesilva]

Kim
A real long shot, check the brake lights and connections. We've had bulbs with fused filiments throw off the cruise in cars.

[nrhareiner]

thank you rick,

If that was the problem would it be intermittent? Also, what would that have to do with the Jake Brake and the lack of the tell tale brake symbol on the dash and the light on the rocker switch?

I had hoped that one of the other relays might play a role, but it appears no such luck.

[Jon Wehrenberg]

Kim,

If someone can run the DDEC codes it might tell the story. You have the kind of problem that drives techs nuts. Unless the cruise has quit when the techs hook up to the DDEC they are apt to not get any codes.

This whole thing could be as simple as loose connections on the back of the switches or it could be a bad ground somewhere or as Rick pointed out it could relate to the brake lights.

[nrhareiner]

Hello Jon,

I have a DDEC reader (actually Silverleaf system) installed. No codes are showing up, even when I check when the problem is active. The brake light is a possibility. If I change the relay in the rear run station (I think 76) could that possibly work? I will be driving the bus again Tuesday.

Thanks

[Jon Wehrenberg]

Kim, There is no downside to changing it, but I doubt if it will have an impact. If no codes are showing up then I suspect there is something external to DDEC that is opening the circuit.

What I cannot yet figure out is how the Jake plays into this. Does your Jake function when the cruise is engaged? On my first coach the Jake was disabled once the cruise was engaged. Your description and the wiring diagrams makes it sound like the Jake does continue to function. If that is the case the fault is likely relating to connections or components between the cruise switches and the Jake. That is solely a guess and since I know diddly about this it could be all wrong.

The thing to focus on would be the components that disengage the cruise, such as brake lights, the disengage switch, the cruise power switch, and anything within that range of items. It still sounds like something is loose and is intermittently opening the circuit.

[nrhareiner]

Hello Jon,

On this bus the Jake does function with the cruise on. I will change the brake light relay just to be complete. I will also check for any loose wires from the switches. I know the Jake works fine even when the cruise will not engage even if the lights on the dash and Jake switch do not function.

[garyde]

Hi Kim. I believe only my middle rear brake light works with my transmission brake, maybe your brake lights are the same. The Central theme seems to be the cruise control dropping out, so I would look closely at all 3 or 4 switches related to the cruise control. (on-off, Set, Resume, Decel) Also, do you have a a telltale light test switch on your Console to illuminate all of your telltale lights and do they all work?
The only other thing I can think it woulld be would be a faulty switch on your brake pedal.

[nrhareiner]

Hello Gary,

I hope that your family and house are okay reference the fires. I do have the ability to check all of the lights, and they all work. All of the brake lights work along with the horizontal light. However, the problem is that I cannot tell when checking standing still if the problem exists at that moment.