Jake Brake problem

[BMB2311]

I have a Cummins ISM 500 in my coach with an Allison 4060 transmission. The Jake Brake will only work in hi (braking with three cylinders). Changing the hi/lo switch makes no difference. I've had the switch out and checked it elecrically and it works fine. The brake is controlled with a foot switch and when I depress it the transmission shifts down to third gear and I can hear the Jake Brake working, but changing the hi/lo switch position makes no difference.

[wolfe10]

The problem could be with the engine or in the wiring to it.

Do you have a wiring diagram of that part of the coach wiring, and does it test out? You know at least part of it does, as the switch does communicate with the Allison ECU and sounds like it activates at least some of the cylinders when engaged.

Here is the number for the Cummins RV Hotline: 800 343-7357, 5

And on HIGH, it should be using all six cylinders (opening the exhaust valves on all six cylinders as the piston approaches TDC on the compression stroke).

On LOW, it should be using three cylinders.

Brett Wolfe

[BMB2311]

I do have the wiring diagram, however the wires don't seem to run where the diagram says they do so I have not been able to trace them out. Thanks for the Cummins RV hotline number. I'll give them a try.