I have seen some where the pedal return spring gets weak, or the clutch release switch is starting to get too far away and the slightest bump in the road causes the pedal to bounce down just a enough to trigger the switch. If your pedal free travel is way too weak on return this will happen. If you just nudge your pedal and the cruise kicks out then you need to adjust the switch so it will not disengage until further in the pedal stroke. Usually you can just bend the mounting bracket the switch is screwed onto to adjust it.
Hope this helps.
FreightLiner Classic Cruise Control
Discussion in 'Trucks [ Eighteen Wheelers ]' started by Firebird, Aug 12, 2009.
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Well, here's the latest. It decided to stop working sitting in front of the garage at the yard. They hooked it up on the computer and couldn't find anything wrong with it. Yet it wouldn't idle up.
Engine running, computer hooked up and computering(?). Cruise on, parking brake on. flip "set" switch, ECM sees it and responds accordingly, but engine speed doesn't increase. All switches: Brake, Clutch, On/Off, Set/Resume/, Parking brake are seen by ecm and reacted to. Yet the engine just doesn't respond. Tapped, heck...beat on the dash and wiggled all the levers and controls and clutch, brake and accelerator, with no results.
Put the truck in gear, released the brake and moved it 5 feet. Everything works perfect. Engine speed increases just as it is supposed to.
What the heck????
Weird stuff going on.
Thanks for all the info and suggestions. We will just keep trying.
Dave -
Should try a road test with a passenger watching the computer and see what is happening. The ECM won't turn off the cruise for no reason, something has to be changing.
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Already tried that too. The guy hooked the computer up and we went for a drive while he recorded it. According to the computer it never happened. It kicked out many times (12 that we counted) but the ecm never saw anything. No event occured that would turn the cruise off.
Here's a new twist to the problem. It ONLY happens with a loaded trailer. It has never happened with a bobtail, and very seldom happens with an empty trailer, but when you put a load on the truck, the cruise kicks out.
I deadheaded 400 miles last week and the cruise never kicked out once. I got loaded and it wouldn't stay engaged at all.
Man this is annoying.
Dave -
And you are sure there are no codes logging in the ECM? Some injector faults will also cause the cruise and engine brakes to kick out to prevent the engine from damaging itself. There may be an issue with an injector faulting only for a split second. If no codes are logging, (they would be inactive with high number of counts), maybe with a loaded trailer the frame is sitting differently causing a wire harness to get stretched. I wonder if the ECM is losing voltage, or ignition power for a split second. With a loaded trailer the injectors will inject for a longer duration, this will draw more current, perhaps you have a power supply issue. Check the power harness to the ECM, it will be it's own plug, 4-5 large gauge wires. Should have it's own power harness to the batteries. I don't suspect a bad ECM, I think if the ECM was failing it wouldn't matter loaded or empty. I know our laptops don't refresh instantly, if there was a problem with the switches and it is happening so fast maybe the laptop can pick it up. Again with a loaded trailer, I wonder if a wire harness is getting pulled too tight. I have seen many times wires ripped right out of connector bodies because they installed too many zip ties and the wires were held down way too tight!
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my freightliner cruise not working on driving, but work on idle
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Don't forget, there is a cruise kick off switch on the Johnny bar/ trailer brake.
Trukdrvr Thanks this. -
Skimmed through the thread and didnt see this.. But do you have clutch free play? About two years ago I had a century class kick out of regen right when it ramped up. Took me a long time to figure out, beacuse the switch was opening so quick, it wouldnt register a transition in the switch on the computer. The clutch pedal was transitioning real quick on and off with high RPM due to the clutch pedal hitting the switch. Kind of a long shot... I know it is a different year and model of truck, but the switches work the same. Make sure you have some freeplay
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FireBird, did you get your cruise working? Im dealing with the samething. I replaced the plastic speed sensor on the back of the transmission near the yoke. That didn't fix the issue. I will replace the Yellow Parking break switch and the brake pedal switch and night as well do the clutch switch. Im hoping you have some insight.
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