Park Brake Not Releasing C2 School Bus from John Whelan on Vimeo.
The park brake on a Thomas C2 school bus has an interlock that requires the service brake to be applied before the park brake releases. Most of the issues we had was the stop lamp module and park brake module located at the air management unit depending on the year of the bus the bank of modules are at the very back in front of the differential housing or behind the transmission.
There was a recall years ago regarding the stop lamp switch located on the right side of the AMU looking towards the back end. The problem was the internal switch wasn't contacting properly so Thomas revised the design and there have been very few problems since then. If you go into accessfreightliner you can bring up the AMU layout for the VIN you're working on.
The park brake light on the dash is a warning to the driver not to drive away with the park brake on, When a driver pulls out the park brake valve the modules sense this and through the J1939 messaging system air pressure changes trigger a signal that is sent back to the dash illuminating the park brake light. When you come to a stop and shut down the engine if the park brake valve is not activated this triggers an alarm until the park brakes are applied.
Unless there's an air leak most of the trouble with AMU modules is the switch contacts. The first check is to see if the brake lights are working if not the stop lamp switch in the module can be tested by jumping the signal to the bulk head module bypassing the internal switch in the module. If the brake lights work there is a problem internally with the stop lamp module.
The same test can be done with the park brake module. In the video the two terminals that sends signals to the BHM are jumped and if the park brake indicator light comes on then there is an internal problem in the module itself. There are only two wires to this module so it's a straight forward test. Most of our troubles have been with these 2 modules.
Also you can not rule out opens and resistance in the wiring harnesses. This is another possibility that you might have to deal with. If you have a Freightliner dealer in your city you need to get a user and password to the accessfreightliner website. Here you will find the schematics and troubleshooting required to fix an electrical problem. Without this information it's very difficult to blindly find an electrical fault especially with multiplexing that's here to stay for a long time.
Showing posts with label thomas bus. Show all posts
Showing posts with label thomas bus. Show all posts
Friday, May 06, 2016
Monday, September 21, 2015
School Bus Pusher Radiator Removal Shortcut
Changing the radiator or removing it for repair at the local radiator repair shop is a big operation on the pusher school bus. The charge air cooler, oil cooler and radiator are sandwiched on top of each other making it hard to get the radiator out of the chassis.
The objective in this video is to show you a short cut that all mechanics love to do saving time and some frustration. The way we do it is to support the upper components and loosen off the radiator mounts. The frame supports have to be loosened as well to allow space so the the rad core can be removed freely.
The cooling fan which is a Parker system is braced to the main frame around the radiator so it needs to be chained up out of the way. In most cases if the radiator is original and has a leak the chances of repairing it is remote I'm sorry to report.
This rad core is over 12 years old and has gone through a lot of weather and road debris kicking up into and around the core area on a daily basis. There are cores out there but we had to get one from Thomas buses. I hope this video helps you bus mechanics out there.
I would appreciate it if you shared or commented on this post. It's great to get some feedback from others who have had similar problems and found a faster way to get them done. Time is a precious commodity in a fleet garage and with that said I'll continue to share videos on repairs that will help out fellow mechanics.
Watch the video below on what our shop did to remove the radiator on a pusher school bus:
Radiator Repair Thomas Pusher School Bus from John Whelan on Vimeo.
The objective in this video is to show you a short cut that all mechanics love to do saving time and some frustration. The way we do it is to support the upper components and loosen off the radiator mounts. The frame supports have to be loosened as well to allow space so the the rad core can be removed freely.
The cooling fan which is a Parker system is braced to the main frame around the radiator so it needs to be chained up out of the way. In most cases if the radiator is original and has a leak the chances of repairing it is remote I'm sorry to report.
This rad core is over 12 years old and has gone through a lot of weather and road debris kicking up into and around the core area on a daily basis. There are cores out there but we had to get one from Thomas buses. I hope this video helps you bus mechanics out there.
I would appreciate it if you shared or commented on this post. It's great to get some feedback from others who have had similar problems and found a faster way to get them done. Time is a precious commodity in a fleet garage and with that said I'll continue to share videos on repairs that will help out fellow mechanics.
Watch the video below on what our shop did to remove the radiator on a pusher school bus:
Radiator Repair Thomas Pusher School Bus from John Whelan on Vimeo.
Thursday, August 13, 2015
A Common School Bus No Start Problem
Thomas School Bus Vandalock
This a common no start problem with all school buses and will continue to be since Vandalocks are standard equipment. The Vandalock as the name states locks out the start circuit and locks the access entries to the inside of the bus. The Thomas pusher in the video does not have any lock out for the entrance doors just the side door and rear emergency exit window.
However there's a cheap and easy solution which is to purchase a metal bike lock (u shaped) and install a couple pieces of angle iron to the entrance door leafs. We only do this with our sports run buses which do a lot of out of town trips. Just recently one of our sports run pusher buses were in Vancouver and the batteries got ripped off.
This is the first time this has ever happened to us perhaps because of the high return for lead at the scrap yard or someone with a truck needed a good set of batteries? Who knows but it's the sign of the times so a lock will be going on both of our sports run battery doors. The service call cost $800.00 in total so a couple of $20.00 hinge locks is a solid investment.
Getting back to the Vandalock system...when we talk to our drivers over the radio we can usually run them through the steps to check all of the exits to see if the latches are either locked or unlocked. One of the students could have very well kicked the latch closed since it's in the perfect spot on the side exit door as seen on the video.
The buzzer will stay on with the ignition key on with no engine crank until the latches are disabled. Vandalock systems are great to have as long as everybody is trained properly.
International School Bus Vandalock
The International school bus vandalock is the same principle as Thomas buses but designed totally different. The conventional models have the entrance door and the rear door set up to lock out access and the engine start system. The video demonstrates how it works but the there is a minor flaw with the lever that activates the micro switch above the entrance door.
This micro switch has to be activated for the bus to start. Every year we have no start problems because of the lever dropping down while the bus is enroute. A rough road condition will cause this and the lever will drop down deactivating the switch causing an engine no start ... alarms will stay on while the ignition is turned on. One solution is to tighten the lever fastener to increase resistance but ever so slightly so the activating rod has enough push to move the lever.
This a common no start problem with all school buses and will continue to be since Vandalocks are standard equipment. The Vandalock as the name states locks out the start circuit and locks the access entries to the inside of the bus. The Thomas pusher in the video does not have any lock out for the entrance doors just the side door and rear emergency exit window.
However there's a cheap and easy solution which is to purchase a metal bike lock (u shaped) and install a couple pieces of angle iron to the entrance door leafs. We only do this with our sports run buses which do a lot of out of town trips. Just recently one of our sports run pusher buses were in Vancouver and the batteries got ripped off.
This is the first time this has ever happened to us perhaps because of the high return for lead at the scrap yard or someone with a truck needed a good set of batteries? Who knows but it's the sign of the times so a lock will be going on both of our sports run battery doors. The service call cost $800.00 in total so a couple of $20.00 hinge locks is a solid investment.
Getting back to the Vandalock system...when we talk to our drivers over the radio we can usually run them through the steps to check all of the exits to see if the latches are either locked or unlocked. One of the students could have very well kicked the latch closed since it's in the perfect spot on the side exit door as seen on the video.
The buzzer will stay on with the ignition key on with no engine crank until the latches are disabled. Vandalock systems are great to have as long as everybody is trained properly.
International School Bus Vandalock
The International school bus vandalock is the same principle as Thomas buses but designed totally different. The conventional models have the entrance door and the rear door set up to lock out access and the engine start system. The video demonstrates how it works but the there is a minor flaw with the lever that activates the micro switch above the entrance door.
This micro switch has to be activated for the bus to start. Every year we have no start problems because of the lever dropping down while the bus is enroute. A rough road condition will cause this and the lever will drop down deactivating the switch causing an engine no start ... alarms will stay on while the ignition is turned on. One solution is to tighten the lever fastener to increase resistance but ever so slightly so the activating rod has enough push to move the lever.
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