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Old 09-26-2021, 05:14 PM   #1
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Join Date: Aug 2019
Location: Auburn, WA
Posts: 779
Year: 2000
Coachwork: IC / Amtran
Chassis: 3000 / 33' Flat Nose
Engine: IC T444E / Allison MT643
Rated Cap: 72 Kids / 48 Adults
Cruise control works, but high idle doesn't?

Since the weather's been warm, I haven't used my high idle in quite a while. The other day I went to use it and it doesn't work.

The same switches that control the high idle, also control the cruise control. My cruise control works just fine.

It sets the speed I want, well Coast to a slower speed or accelerate to a higher speed using the set resume switch and it will resume Cruz after tapping the break.

I did try to use the accelerator pedal to increase the RPMs and then set the high idle, but that didn't work.

I have two rocker switches, one that turns the cruise control on, and another that sets the speed, or allows you to Coast, accelerate or resume cruise control.

With the bus running and in neutral, and the cruise control on off switch in either position, I use the other switch to try and increase the RPMs, and it doesn't work.

I don't think gear position is a factor, must be in neutral for high idle to work or being drive for cruise control to work. Yet maybe?

So you don't have to look at my profile, my bus is a 2000 amtran/ic model 3000 rear engine with it t44444e 7.3 engine.

I do not have a PTO, which uses many of the same connections.

I have servicing and troubleshooting documents that I've been referring to and following.

What am I missing? In relation to this issue, no personal comments necessary! Ha.

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Old 09-26-2021, 05:26 PM   #2
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Location: Southern Oregon
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Year: 1996
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I'll be watching as I have a 96 AmTran (IH) with no cruise but High idle works fine. I think mine is a programing setting from the school district as it's limited to 55 road speed as well.
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Old 09-26-2021, 06:44 PM   #3
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I believe your high idle is adjusted with your foot, not the switch, while in neutral.
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Old 09-26-2021, 09:17 PM   #4
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the high idle can be set with the dash switch and its selectable in the computer.. you an have cruise without high idle, you can have high idle without cruise..



id often say its one of the 2 brake switches but that will disable both cruise and high idle for the key cycle...
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Old 09-26-2021, 11:31 PM   #5
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Join Date: Aug 2019
Location: Auburn, WA
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Year: 2000
Coachwork: IC / Amtran
Chassis: 3000 / 33' Flat Nose
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Quote:
Originally Posted by cadillackid View Post
the high idle can be set with the dash switch and its selectable in the computer.. you an have cruise without high idle, you can have high idle without cruise..



id often say its one of the 2 brake switches but that will disable both cruise and high idle for the key cycle...
That's what is confusing me. All the schematics I see keep using the same terminals and wire numbers, and since the cruise control works, I understand why the high idle doesn't.

Funny, they mentioned cruise control, PTO, etc. But they don't say anything about high idle in the service or diagnostic manuals. At least nothing I'm finding.

It's a definite head scratcher!
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Old 09-30-2021, 01:47 PM   #6
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Join Date: Aug 2019
Location: Auburn, WA
Posts: 779
Year: 2000
Coachwork: IC / Amtran
Chassis: 3000 / 33' Flat Nose
Engine: IC T444E / Allison MT643
Rated Cap: 72 Kids / 48 Adults
The mechanic suit my work, who getting any friendly assistance from is like pulling teeth, thought it might have something to do with the parking brake and an electrical switcher sensor.

This would make some sense, because the parking brake wouldn't be applied when driving down the road and using the cruise control. But, when you're parked and want to use a PTO or a high idle, which I'm coming to suspect or considered somewhat same thing, at least in this case, you have to have the brake generally set.
So I got under the dash and took a couple of pictures. Coming out the back of the parking brake or for airlines, and two of them laid down to these two electrical connections.

NOTE: the picture of the electrical air connection shows only the orange air hose, but right behind it going into the second connector is a green air hose.

I don't know what these two things do. Do any of you?

I looked for any kind of schematics to help me know what these air electrical connectors are, but I can't find anything. If anybody has any bodybuilder documentation for my bus, I would appreciate a copy of it.

Thanks!
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Old 10-13-2021, 09:58 PM   #7
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The engine ECM has parameters to control the high idle functionality. If they are turned off you’d have no chance of using the cruise switches to ramp the engine. The high idle parameters are all in the 75_ _ _ range (that refers to parameter ID numbers). If you have servicmaxx 1708 software (freeware) and a nexiq clone cable (cheap on eBay or alibaba) you can check those parameters out yourself and change them if necessary.
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