BAC Forum
General Boards => Technical Support => Topic started by: Bryan Beamon on December 13, 2024, 08:13:25 PM
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Our exhaust brake is not working on our Cat C9 400hp. In trouble shooting with Pacbrake they seem to think the solenoid is not getting the signal to activate the Pacbrake. Having difficulty locating the relay. I found the solenoid and found the ground wire but tracing the second wire to the relay has me stumped
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Bryan
On page #2 of the 2007 contessa wiring diagram found in coach assist library shows relay R18 as the exhaust brake relay.
It is to be noted that the exhaust brake is controlled through the engine ECM ( engine control module ) in conjunction with the TCM ( Transmission control module )
The exhaust brake relay ties into the brake light relay so the brake lights activate during exhaust brake operation.
If a following car can see brake lights under exhaust brake conditions the ECM is sending a signal to activate the exhaust brake.
Hope this helps
Eric
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Eric, thank you. Do the Attached photos designate the relay you describe? I was confused by the description on the relay in my front service bay saying exhaust brake sol.
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Second photo
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Bryan
Yes the relay is labeled exhaust brake solenoid: because it sends the signal to the air solenoid that operates the exhaust brake.
Eric
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As you know, the C9 uses a "Pacbrake" instead of the internal compression brake used on larger models. It's commonly on our rigs made by Jacob's Systems, but is for all intents a twin of the original Pacbrake. Before I'd get into the electrics, I'd check the cylinder operation and whether the butterfly flapper moves freely; they often seize from lack of regular lubrication. Also see that airlines aren't leaking and the solenoid hasn't corroded up, or wires failed there where heat and exposure is greatest; kudos for having already found the solenoid. I keep a bottle of lube and try to remember to apply it every so often as prescribed, usually at least prior to or after "storage" periods. I believe there may be a guide to lubing in the brake section of Coach Assist. Also of course is the common oops of having both the exhaust brake and cruise control switches on at the same time.
Joel
https://www.youtube.com/watch?v=9QxZhk_CUB8
https://pacbrake.com/superlube-exhaust-brake-lubricant.html?gad_source=1&gbraid=0AAAAAqs6Wyd1ZS1QKcilDLjT_0gFaYVF_&gclid=Cj0KCQiA0--6BhCBARIsADYqyL9m0bmU9wRLim4-GVW24NKT144Bm4EihrDLjNyF_Q8iZgioHog-F4saAkm-EALw_wcB
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Joel,
On the 07 the exhaust brake works with the CC on. Makes driving a bit more convenient. Only downside is that with the exhaust brake on the power steering will sometimes "buck" at slow speeds as noted in previous threads.
Steve
Bryan,
If you haven't, suggest you print pgs 2 & 4-7 of the 07 Contessa wiring diagrams (relay & fuse location and fuse ID info). Put them in plastic sheet protectors and leave them in the forward electrical bay. (I taped pg 2 to the inside of the bay door). Saves a lot of hassle when you need to check on a fuse or relay.
Steve