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Old 08-12-2014, 08:42 PM   #1
Join Date: Nov 2012
Posts: 78
PAC Brake not Activating

When I take my foot off the throttle I get no downshift & no brake activation. I have checked the fuse for the PAC Brake. If I energize the solenoid with 12v the air cylinder does close the exaust butterfly. Any ideas?

Wayne Cadieu
2008 Allegro Bus 43 QRP
Cummings ISL
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Old 08-12-2014, 10:09 PM   #2
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Join Date: Jul 2011
Location: B.C.
Posts: 3,939
Try turning off the cruise control. The truck I drive with a Cat C12, will not let the Jake work with the cruise on. I know it is different than a pac brake but worth a try. My coach with a ISC Cummins will sometimes do the same thing.

Dennis & Marcie & Captain Hook The Jack Russell,aka PUP, 1998 HR Imperial 40 ft RVM59
A good day on the road means a better night at the park!
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Old 08-12-2014, 10:19 PM   #3
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Join Date: Apr 2011
Location: Powell River, B.C.
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Could be a communication problem or a relay .
System wants to see , zero throttle signal from the TPS, so binding pedal due to carpet ; or as was my case rusted hinge. Others have reported switch trouble , not passing power to the system even though the light is on. With the no downshift displayed I'd, look at the switch. If the trans control showed 2 and no activation I'd think relay.
You would need a wiring schematic for your coach to track down a relay , if in fact it has one , but most do.
My coach has 2 relays for exhaust brake and I don't know why , and hope I never have to find out.
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.
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