Cruise contril quit working

[captain ron]

Last year when I was headed back to Florida I had to slam on my brakes and my cruise quit workinf for a while then started working again. I had to get on the binders hard again and it quit working all together. The green light on the dash comes on when I start the bus indicating that the cruise is working but it is not. I have a 740A Atec allison. any help or sugestions?

[rv_safetyman]

Hi Ron.  Need to know if your engine is mechanical or DDEC.  If DDEC, I might be able to help you.

[RTS/Daytona]

Ron

Is the Green light just a "power on type light" and not an "cruise control engaged" light ??

If it's only the power light - and it's  will not "engage" after your heavy braking incidents - Perhaps you should look for the brake switch being stuck - or a wire loose on the brake switch tap (after market style cruise controls)

Pete RTS/Daytona

[bobofthenorth]

I'd echo what Pete said plus you could check to make sure you don't have a brake bulb burnt out or corrosion preventing contact.  Cruise controls sense ground through the brake circuit and turn off if they can't see ground. 

[captain ron]

The engine is DDEC and the green light is a power on light and an engaged light. I did have a brake light out but now all fixed and also believe I have some electrical issues but not even sure where to start on that.

Allso how do you get the "NEW" button on your posts? mine always seem to get pushed to the second page and moved around. much different than the board I'm used to

[belfert]

Allso how do you get the "NEW" button on your posts? mine always seem to get pushed to the second page and moved around. much different than the board I'm used to

The new only shows up for each reader.  You won't see the new button if you just started a topic or replied to one as the topic isn't new for you.

Topics get moved to the top every time someone replies to the topic.  If nobody replies for a while, your topic will fall to the second page.

Brian Elfert

[rv_safetyman]

Hi Ron.  There are two control switches (three if you had a clutch) that can keep the cruise control from working.  One is the brake switch that deactivates the cruise and the second is the switch for the parking brake.  If the ECM thinks that the brakes are applied or the parking brake is applied, the cruise will not work. 

On my eagle both cruise control pressure switches are in the area below the breakers on the outside panel below the driver's side window. 

Since you have had issues with the brake lights, I would guess the service brake system would be the place to start.  It sounds like the pressure switch for the cruise control  thinks there is pressure.  In this case, disconnect one wire from each pressure switch you find (one at a time) and see if the fast idle will work.  If the high speed idle will work, you will more than likely have cruise control. 

If that does not work, then short each pressure switch (ie close the circuit) to test if the parking brake switch is bad. 

On the Eagle, I think there are at least four pressure switches to play with.

I don't think any bus has a mechanical switch on brake pedal.  If yours does, that would be the first thing I would play with (would probably be an adjustment issue).

Let us know what you find.  If this does not do the job, we will try some other things.

[NJT5047]

If you have DDEC cruise control, as Jim says, the brake switch sounds like a good place to start looking.  The wiring for an MCI  cruise brake interlock is under the drivers seat.   The switch is mounted on or adjacent to the the treadle valve.  It is a NC/NO switch with a common terminal (3 terminals total).  The DDEC must see a "brake off" signal to function.   However, the "enable" light would correctly come on and go off with a brake light "on" signal.  This would be similar to cranking the bus with the park brake set.  The brake "on" is not a fault.  This may give you an idea of what is causing your problem. 
The green light is an "enable" light, and should operate the same as an engine CEL...the engine CEL and cruise enable light come on when the ignition key is turned on, and go off together.  If the green "enable" light doesn't come on, the system sees a fault.   If the ECM doesn't see a "brake off" signal, or sees a "brake on" signal (in error) it won't set.   There should be two lights on a DDEC cruise...the "power on" doens't mean bo....it is just a power light that indicates the switch is in the "on" postion.  The product of a DPST switch.  The "on" light is not actually a part of the cruise control.  The enable light is.   The cruise enable light comes on each time the ignition switch is turned on, whether the cruise is on or not. 
Do your brake lights work correctly....a blown bulb won't alter the DDEC cruise function...but hanging brake light would... the switch that controls trhe brake lights may be a separate unit, or could be operating a  DPST solenoid.   Keep in mind that the DDEC brake signal is not a "hot" (B+) signal.  Don't short or jump anything in the ECM wiring harness.  All the cruise circuits complete a system of grounds...from which the ECM sorts out the signals.   None have 12V or 24V on them.   To add yet another layer of confusion, the brake light system is not typiclaly wired to the bus brake lights...two separate switches...although the switch could be one unit with all functions. 
This is assuming you have a DDEC system.   The system is simple, but the "set,"  "resume," and "brake" all have both "off" and "on" positions.  In other words, the system makes a circuit in both the off and on postions. The function can be easily checked at the ECM.   Only three circuits control a DDEC unit.
If you have a Rostra, or any mechanical linkage attached to the accel pedal, the above doens't apply, however, the brake switch is still a good place to start.
Locating an "applied" brake signal is easy to consider, but the "brake off" signal is an oddity.   Reckon it's sorta super safe.
All of the cruise wiring on a DDEC unit is beneath the drivers seat and in the LH switch panel. 
If you deternine you have a DDEC cruise, and need the wiring color codes, let me know.  I'll forward them to you. 
If my memory serves me (very iffy!) you have a retrofit DDEC II engine and trans.    Hope this helps!
Best, JR