Jake Brake

[becker]

I am (was on the road when I started posting this message). I have a 2008 Monaco Dynasty 425hp Cummins with a Allison 3000 MH 6-Speed World Transmission and Electronic Shifter. Normally on steep downhill grades I can flip the Jake Brake on and it will hold the speed I want.... normally 50mph. Now it will not only not hold the speed but the switch feels like it is not connected….. I can flip it back and forth and nothing happens. There is a second Jake Brake (Hi/Lo switch) and it works fine next to the Jake Brake that I use for speed retention and to slow down when I approach a town speed limit (35mph). I generally only use the second Jake Brake when I am below 40mph and it takes me down to 15mph then turns loose.
My question is: Has anyone else experienced this and is it something I can fix? I appreciate your input.... maybe all of sudden I am not operating them correctly.

becker

[beenthere]

oh wrong thouhgt

[slickest1]

The main switch will turn the jake brake on and off. The high low switch does just that. When the switch is in the high position you get the full brake force from all cylinders of the engine. When on low it only uses 2 or 4 ( I'm not sure on that) cylinders. The high low switch should not work with the main switch off.

I am not sure why your switch is not working. On some units the jake will not work with the cruise on. I would check for a fuse in your electrical panel.

[Gary RVRoamer]

What slickest1 says. You only have one jake brake, and there is an on/off switch as well as a high/low setting that selects the amount of braking when the main switch is on. The selection is all cylinders braking or half of them, which means 6 cylinders or 3 cylinders in the case of your 425 hp Cummins.

It sounds like the On/Off switch has physically broken, i.e.isn't switching any more.

[BrianGlenn]

If you want to replace the switch yourself - I have used Ancor rocker switches for replacements in the past; it sound like the main on/off would be a single pole, single throw (SPST) switch. Ancor switch, non lighted SPST model 554010 here. You will need to confirm the dimensions fit into your slot in the dash.

The high low switch may be a Single Pole Double Throw (SPDT) or Double Pole Double Throw (DPDT) depending on how it was wired from factory.

You can pull the switch to look at the number of connections to confirm; and SPST will have 2 connections, SPDT will have 3 connections and a DPDT will have 6 connections.

When the switch is described in the literature be aware of Terminology On-Off-On and (On)-Off-(On) where the brackets around the "(On)" designate "Momentary" - i.e. you have to hold the switch in the on position and then it "pops back" to off. Not used in this case, but is usually used in landing gear legs on 5vers etc.

Hope this helps,
Brian