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 C2 Park Brake will not release
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aaronwilmoth80911
Senior Member

147 Posts

Posted - 08/07/2014 :  06:28:52 AM  Show Profile  Visit aaronwilmoth80911's Homepage  Reply with Quote
2008 C2 w/air brakes, park brake will not release. This bus also has a wheelchair lift as well. I am not the one working on this, one of our other mechanics is. I know he has changed 2 of the blocks on the AMU, but I'm not sure which ones. I'm not sure what else he has done. He says the park brake will not release, and just dumps air when the valve is pushed in. Also the range inhibit light comes on when trying to be put in gear. It is the first day of school today, and we have been slammed all week with drivers coming back and checking their buses and what not, so I am not in much of a position to be able to help him other than trying to reach out for some help from the community. Thanks guys!!

Fastback
Top Member

992 Posts

Posted - 08/07/2014 :  06:47:44 AM  Show Profile  Reply with Quote
Make sure there is no problem with the lift switches/safety interlocks and wiring to the bus.

Why yes, the ORIGinal CHARGER is a Fastback

Edited by - Fastback on 08/07/2014 06:48:18 AM
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Thomasbus24
Administrator

USA
3362 Posts

Posted - 08/07/2014 :  08:55:54 AM  Show Profile  Reply with Quote
What you have there is a 100%, certified nightmare bus. They have one where I used to work set up the same way and it does the same crap.

Start cleaning connections. All of them. Lots of them UNDER the bus that get nasty and freak the stupid thing out.
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willism
Senior Member

United States
143 Posts

Posted - 08/07/2014 :  09:18:52 AM  Show Profile  Visit willism's Homepage  Reply with Quote
Had one last year same issue needed a new computer by the left front wheel cant remember what that one was called.
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aaronwilmoth80911
Senior Member

147 Posts

Posted - 08/08/2014 :  06:22:53 AM  Show Profile  Visit aaronwilmoth80911's Homepage  Reply with Quote
Thanks guys. We are waiting on a different block for the AMU to see if that fixes it. We borrowed a block from a neighboring district, but it apparently was not the correct one, so until we get the right one, we are still trying to diagnose, but are at somewhat of an impass with it. I'll let you know what we find out when we get this new block.
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tigger2
Advanced Member

USA
286 Posts

Posted - 08/08/2014 :  08:46:34 AM  Show Profile  Reply with Quote
Make sure the lift switch is turned off and make a full aplication of ths service brake WHILE yuo push in the parking break knob.Part of the interlock is one or two double check valves that have to be in the right position to release the brakes.
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aaronwilmoth80911
Senior Member

147 Posts

Posted - 08/08/2014 :  08:52:55 AM  Show Profile  Visit aaronwilmoth80911's Homepage  Reply with Quote
Thanks guys. We are waiting on a different block for the AMU to see if that fixes it. We borrowed a block from a neighboring district, but it apparently was not the correct one, so until we get the right one, we are still trying to diagnose, but are at somewhat of an impass with it. I'll let you know what we find out when we get this new block.
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Winn10
Active Member

27 Posts

Posted - 08/09/2014 :  05:58:56 AM  Show Profile  Visit Winn10's Homepage  Reply with Quote
there is a fuse on the fender mounted PDM (f19 if im not mistaken)that can blow and cause the same problem. like said before make sure lift switch is OFF. if it was the amu module causing it then your brake lights will not work, something to check b4 spending money on a part.
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aaronwilmoth80911
Senior Member

147 Posts

Posted - 08/11/2014 :  06:11:55 AM  Show Profile  Visit aaronwilmoth80911's Homepage  Reply with Quote
Lift switch is off, verified that the switch is working correctly with CAT ET (will cause pto status to be on). Brake lights are not working, so we ordered the AMU with the service brake switch in it. Not sure of its status as of this morning, mechanic working on it is not here yet. Will update as soon as I find out more info.
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Bus Tech II
Senior Member

111 Posts

Posted - 08/11/2014 :  11:45:54 AM  Show Profile  Visit Bus Tech II's Homepage  Reply with Quote
look for wiring chaffe at head of air compressor. We have had several chaffe here and cause all kinds of problems with AMU and after treatment functions
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aaronwilmoth80911
Senior Member

147 Posts

Posted - 08/12/2014 :  06:51:01 AM  Show Profile  Visit aaronwilmoth80911's Homepage  Reply with Quote
New info that I didn't know before: when the lift switch is turned on, it automatically bumps up to a high idle, when it is being turned off though, it is not coming back down to low idle. Mechanic from neighboring district who runs primarily C2s says that there is a smart switch that is malfunctioning which is causing it not to let park brake release. I'm not sure how this can be as the PTO is showing on and off on CAT ET when the switch is turned on/off, but I'm no expert on C2s and their smart switches. Apparently the AMU block that was ordered was the same one as one that was already replaced, even though the part numbers did not cross. As I said before, I am not the primary party working on this, just trying to help a guy out. I will pass along more of this information and let you know what we find out. Thanks!!
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Fastback
Top Member

992 Posts

Posted - 08/12/2014 :  07:12:00 AM  Show Profile  Reply with Quote
One thing to remember on the C2 multiplex wiring is that most components have power to them at all times, its the grounds that the controllers are switching on and off. Example; ground a dome lamp with too long of screws and the dome lamp won't shut off. In no way saying this is the problem with this bus, just be sure no component is getting an "extra" or alternate ground anywhere.

Why yes, the ORIGinal CHARGER is a Fastback

Edited by - Fastback on 08/12/2014 07:13:47 AM
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aaronwilmoth80911
Senior Member

147 Posts

Posted - 08/15/2014 :  09:41:41 AM  Show Profile  Visit aaronwilmoth80911's Homepage  Reply with Quote
This has now become my ordeal, so I need some info. Can anyone tell me where the switch hub module is located?
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willism
Senior Member

United States
143 Posts

Posted - 08/15/2014 :  10:32:45 AM  Show Profile  Visit willism's Homepage  Reply with Quote
down behind the left fender i thought
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Bus Tech II
Senior Member

111 Posts

Posted - 08/15/2014 :  10:45:39 AM  Show Profile  Visit Bus Tech II's Homepage  Reply with Quote
Switch hub module is inder the switch panel. Chasis hub modues are under left fender
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aaronwilmoth80911
Senior Member

147 Posts

Posted - 08/15/2014 :  1:21:11 PM  Show Profile  Visit aaronwilmoth80911's Homepage  Reply with Quote
Found it. It is indeed in the switch panel. I jumped the pins on the AMU connector and still had no signal to the SHM. Started tracing the wire from the AMU to the CHM and had no continuity there either. Found that the wire from the AMU is corroded and broken about an inch behind the connector. Getting the weatherpack style connector and will repair the wire on Monday. Thanks for all the input and I will let you all know if this fixes it. Have a good weekend everybody!!!
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aaronwilmoth80911
Senior Member

147 Posts

Posted - 08/19/2014 :  08:05:12 AM  Show Profile  Visit aaronwilmoth80911's Homepage  Reply with Quote
Ok, I repaired the wire and now have a good signal up to the switch hub module and am able to release my park brake. Hooray. Now when I take my foot off the service brake, it dumps air out of one of the AMUs. The problem before is that it dumped air when trying to release the park brake, now it seems as if the problem has changed from park brake to service brake. I'm pretty lost at this point and am trying to run some more tests on things, but anymore input would be appreciated.
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aaronwilmoth80911
Senior Member

147 Posts

Posted - 08/20/2014 :  10:57:16 AM  Show Profile  Visit aaronwilmoth80911's Homepage  Reply with Quote
Problem solved. One of the AMUs that was previously changed by the other mechanic was not the right AMU. This caused the service brake to dump air when it was released. Put the old AMUs back in and it is back to where it should be.
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Fastback
Top Member

992 Posts

Posted - 08/21/2014 :  05:31:43 AM  Show Profile  Reply with Quote
Thanks for the update.

Why yes, the ORIGinal CHARGER is a Fastback
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