I want high idle

OK, switch on the park brake?? where is it?? I crawled under the dash and didn't see any wires coming out of the brake switch... Where do Look now??

msmith1199 wrote:
I don't know much about MH cruise controls, but on cars I'm pretty sure most cruise controls are using the actual speed of the vehicle and not the RPM of the engine. I'm not quite understanding why the cruise control would work to keep the RPM's up on a vehicle that is sitting still. Is this just a feature that is built in to cruise controls that are installed on diesels just for the high RPM idle?

Most truck drivers will run their engine all night while they are sleeping to either run air condition or heat. Both of those work better at high idle. Plus running a big diesel at idle for an extended period of time is not good for a number of reasons. Not too sure why they carried this over to motor homes as we usually don't need to run them while we are sleeping. I like it to build air pressure quicker.

JackMS wrote:
That is why my first guess would be parking brake switch. If the ECM sees no road speed, it requires the parking brake to be set to raise rpm. When all is working and your are on high idle, if you release the parking brake, engine will go back to idle, at least on trucks. Never tried on my MH.

A shop should be able to diagnose this fairly quickly. Probably 10 minutes. They may have a minimum 1 hours charge or a flat rate for diagnosis, but you could fix it after they lead you in the right direction. Or if you could find your parking brake switch, you could take the 2 wires and disconnect them. If that doesn't work, connect the 2 together and try that. That will simulate the switch being open and closed.

Thanks, I will certainly try that.. Not sure where the switch is on the EBrakes, i'm sure I can find it.. Thanks again.

I don't know much about MH cruise controls, but on cars I'm pretty sure most cruise controls are using the actual speed of the vehicle and not the RPM of the engine. I'm not quite understanding why the cruise control would work to keep the RPM's up on a vehicle that is sitting still. Is this just a feature that is built in to cruise controls that are installed on diesels just for the high RPM idle?

Mr. Coach - I did some searching and found this little bit of information.

The early 2000 DS's did not have the feature to go to high speed idle. They had a MD3060 transmission and it was not programed for high idle. The late model 2000 DS's had a MH3000 transmission with the high idle feature. To set high idle start the engine and leave it in neutral, turn on the cruise control and press the set button. The idle will increase to 1000 rpm. Turn the cruise off or press the brake pedal to go back to normal idle.

So before you go digging too deep, figure out which Allison Transmission you have and you will know if high idle was a factory feature.

As one that does use my coach in colder weather, high idle is a must to build any heat in the motor. Even with the block heater going, when its under 40F it takes a long time for temps to build. And that means no dash heat and harder on some of the drive train. And yes, since the motor is idled up it does build up air pressure faster.

That is why my first guess would be parking brake switch. If the ECM sees no road speed, it requires the parking brake to be set to raise rpm. When all is working and your are on high idle, if you release the parking brake, engine will go back to idle, at least on trucks. Never tried on my MH.

A shop should be able to diagnose this fairly quickly. Probably 10 minutes. They may have a minimum 1 hours charge or a flat rate for diagnosis, but you could fix it after they lead you in the right direction. Or if you could find your parking brake switch, you could take the 2 wires and disconnect them. If that doesn't work, connect the 2 together and try that. That will simulate the switch being open and closed.

Ok, I've tried everything you all have said and ends up to nothing.. Yes my cruise actually works going down the road, and I don't understand why it wouldn't work sitting still. Maybe because the wheels aren't spinning it wont go into cruise mode:h I don't know.. I'll have to do some more checking though.. thanks

Could be your parking brake switch is not working. Not sure on MH's but on trucks, it lets the ECM know the parking brake is set, which is required for high idle to work. Could also be that your ECM is not programmed for this option. Either issue can be solved at a cummins authorized dealer or any other place that has Cummins Insite on a laptop. We deal with high idle and cruise issues at work a lot. The first thing we do is connect laptop and see what ECM is reading as far as switch positions.

Could also be your service brake switch but if your cruise works going down the road and the brake kicks the cruise off, then it's probably not that.

I use high idle to build air quicker so I'm not the guy sitting there forever with engine running. Get everything else ready. Start engine and gen, go to high idle, unplug shore power, drive away.

Did anyone mention that the Pac/jake/retarder must be off for this to work? Also if the brake lites are on for any reason it won't work either.
Ron