Go Back   iRV2 Forums > THE OWNER'S CORNER FORUMS > Alpine Coach Owner's Forum
Click Here to Login
Join iRV2 Today

Mission Statement: Supporting thoughtful exchange of knowledge, values and experience among RV enthusiasts.
Reply
 
Thread Tools Search this Thread Display Modes
 
Old 10-13-2015, 01:41 PM   #1
Junior Member
 
Join Date: Feb 2015
Posts: 24
Pac Brake inactive temporarily

2001 Alpine 36FDDS 350ISC w Pac Brake: Approaching a stop I switched on the Pac Brake and it didn't activate. Several more stops over the next hour, flipped the switch on & off a few times, but no braking action and no engine RPM change. We were about to head over 2 Cascades mountain passes, so I pulled in to a rest stop, shut off the engine for about 10 minutes, and restarted. Pac Brake activity returned in all its wonderful effectiveness. This has happened only once before a couple of months ago, and an engine shut-off and restart fixed it then also. I have lubed the Pac Brake with their special oil a couple of months ago.

So my problem is probably electrical, and probably not the switch itself, but perhaps some relay that's activated by engine startup. Any ideas on what may be happening?

Commentary on Pac Brake: I've heard that the engine valve Jake Brake is better, but I don't know how, because this Pac Brake is fantastic! Appalachians, Sierras & Cascades - no mountain pass or 7% downgrade has ever required any more than an occasional light touch on the brake pedal to keep us at 60 mph or below. As we coast down and gain speed, I switch it on at 65 mph and it kicks down to 5th gear. As it slows to below 60 mph it kicks down again to 4th gear and really brakes hard. I just toggle the switch on & off as needed, and touch the brake pedal if there are any tight turns. But that's all that is ever necessary. Fantastic system!

Michael
2001 Alpine 36FDDS
__________________

__________________
mbweitz is offline   Reply With Quote
Join the #1 RV Forum Today - It's Totally Free!

iRV2.com RV Community - Are you about to start a new improvement on your RV or need some help with some maintenance? Do you need advice on what products to buy? Or maybe you can give others some advice? No matter where you fit in you'll find that iRV2 is a great community to join. Best of all it's totally FREE!

You are currently viewing our boards as a guest so you have limited access to our community. Please take the time to register and you will gain a lot of great new features including; the ability to participate in discussions, network with other RV owners, see fewer ads, upload photographs, create an RV blog, send private messages and so much, much more!

Old 10-13-2015, 02:39 PM   #2
Senior Member
 
BFlinn181's Avatar
 
Gulf Streamers Club
Join Date: Jan 2012
Location: Cincinnati
Posts: 16,208


I can't help you with the PAC brake issue, but your post mentions 'touching the brakes.' Light application of brakes for a period of time is a sure way to build heat and eventual brake fade or failure. Apply the brakes firmly to slow down at least 10 mph then physically remove foot from the treadle until you need to apply them again. I've lived in hilly areas most of my life and I see many examples of people riding the brakes lightly to control speed going downhill. This is usually brought to my attention as I smell overheated brake lining.
__________________

__________________

Bob & Donna
'98 Gulf Stream Sun Voyager DP being pushed by a '00 Beetle TDI
BFlinn181 is offline   Reply With Quote
Old 10-13-2015, 04:28 PM   #3
Senior Member
 
Join Date: Oct 2014
Posts: 523
First thing to check is the throttle switch. Until the relay sees no throttle, it will NOT allow the exhaust brake signal to go to the Allison ECM or on to the exhaust brake solenoid.

The fact that the shift pad does not change from "6" says the problem is "up front".

Brett
38 FDDS
__________________
wolfe10 is offline   Reply With Quote
Old 10-13-2015, 04:57 PM   #4
Junior Member
 
Join Date: Feb 2015
Posts: 24
Bob, by "occasional light touch on the brake pedal" I mean light touch, up to 5 seconds long, only occasionally when approaching tight curves. My brake pads spend very little time touching the rotors. I know never to 'ride the brakes'.

Brett, where would I find the throttle switch? And how would I check it considering that it works 95% of the time? Perhaps it's best to just replace it.

Also, in D drive, my shift pad always shows a "6" unless I manually downshift. It never displays the actual gear the transmission is in when it changes automatically.

Michael
2001 Alpine 36FDDS
__________________
mbweitz is offline   Reply With Quote
Old 10-13-2015, 05:06 PM   #5
Senior Member
 
Join Date: Oct 2014
Posts: 523
Michael,

Sorry, have not looked for the throttle switch yet on the Alpine-- I am sure someone else will offer advice.

As far as the Allison shift window showing "6" all the time. NO, that is not correct. The window shows the "pre-select" gear. In other words, under ideal conditions that is the gear TOWARD WHICH the transmission will shift.

So, for example in "D", even at a full stop, it will show "6", as that is the gear toward which it will go as long as it keeps the engine within its RPM range.

OK, now with the exhaust brake turned on, the pre-select gear can be anything, but normally 2nd or 4th. Yes, it could be 6th, but in hundreds of coach mechanical inspections I have done, have not run into that yet. So, please verify that the shift window does not change from 6th to some lower gear when the exhaust brake is working. And, of course, the transmission should downshift toward that gear as well.

Brett
2003 38' FDDS
__________________
wolfe10 is offline   Reply With Quote
Old 10-13-2015, 06:20 PM   #6
Junior Member
 
Join Date: Feb 2015
Posts: 24
Brett
Thanks for the explanation that the shift window shows the gear toward which the transmission will shift. I probably haven't looked down at the window when the pac brake is on because that's usually when we're careening down a 7% grade, and my eyes are glued to the road ahead! Maybe mine is working properly. I'll check that next time we're on the road.

But I still don't know why the pac brake hasn't activated a couple of times when switched on.

Michael
2001 Alpine 36FDDS
__________________
mbweitz is offline   Reply With Quote
Old 10-13-2015, 06:33 PM   #7
Senior Member
 
bcbowers's Avatar
 
Alpine Owners Club
Join Date: Mar 2009
Location: Surprise, AZ
Posts: 631
I'm not sure about a PAC Brake but my Jake brake will not activate if you're traveling too fast for the transmission to downshift. Could this be the case? I think around 62 MPH my transmission will find 5th gear with limited back-flow and then fully engage at about 62.
__________________
Bob Bowers (Surprise, AZ)
2003 Alpine Coach 40' FDTS
2014 Jeep Cherokee Lattitude
bcbowers is offline   Reply With Quote
Old 10-13-2015, 08:05 PM   #8
Senior Member
 
Join Date: Oct 2014
Posts: 523
Michael,

Next time you are on the road, tell us what the Allison shift window does in relation to the exhaust brake working/not working.

That will certainly help point toward the root cause of the problem.
__________________
wolfe10 is offline   Reply With Quote
Old 10-13-2015, 10:29 PM   #9
Member
 
Winnebago Owners Club
Freightliner Owners Club
Join Date: Feb 2015
Location: BC
Posts: 60
Quote:
Originally Posted by wolfe10 View Post
Michael,

Sorry, have not looked for the throttle switch yet on the Alpine-- I am sure someone else will offer advice.

As far as the Allison shift window showing "6" all the time. NO, that is not correct. The window shows the "pre-select" gear. In other words, under ideal conditions that is the gear TOWARD WHICH the transmission will shift.

So, for example in "D", even at a full stop, it will show "6", as that is the gear toward which it will go as long as it keeps the engine within its RPM range.

OK, now with the exhaust brake turned on, the pre-select gear can be anything, but normally 2nd or 4th. Yes, it could be 6th, but in hundreds of coach mechanical inspections I have done, have not run into that yet. So, please verify that the shift window does not change from 6th to some lower gear when the exhaust brake is working. And, of course, the transmission should downshift toward that gear as well.

Brett
2003 38' FDDS
Hi
Just to confuse thing more. When I bought my MH my exhaust brake preselected 4th every time I turned it on. I found that the aggressive downshift every time I used my exhaust brake was too much.
I had Allison reprogram my trany (3060) so that no preselect occurs when I activate my exhaust brake. In other words I select when the exhaust brake is on and I select the gear. With the exhaust brake on though the downshifting is a little more aggressive.
John
__________________
1999 Winnebago Chieftain
1992 Jeep YJ
1984 Harley Liberty edition
jporietis is offline   Reply With Quote
Old 10-14-2015, 07:58 AM   #10
Senior Member
 
Join Date: Oct 2014
Posts: 523
John,

I happen to agree and have had the Allison ECM on our two previous coaches reprogrammed for 5th gear pre-select for exhaust brake.

There is NO ideal choice. In mountains, 5th gear pre-select gives the driver more choices with the use of the down and up arrows. Example, headed west on I40 into Albuquerque, 5th with exhaust brake on for 11 miles is perfect. 4th is too much braking HP and no exhaust brake is too little.

When coming to a stop, 2nd gear pre-select is a better choice.

For those with a 4th gear or lower pre-select who experience a harsh initial downshift when the exhaust brake is applied, here is what can happen ALL AT THE SAME TIME: If speed is low enough in 6th, the transmission can downshift directly to 4th gear AND the exhaust brake can be applied. Yes, at higher speeds, it shifts to 5th and then later to 4th as speed drops.

To eliminate that harsh braking divide the braking into three parts:
1. Down arrow to 5th.
2. Down arrow again to 4th. The Allison will NOT downshift until speed is low enough.
3. Turn on exhaust brake.

Now you "ain't throwing momma through the windshield".

Brett
2003 Alpine 38FDDS
__________________
wolfe10 is offline   Reply With Quote
Old 12-06-2015, 08:12 PM   #11
Junior Member
 
Join Date: Feb 2015
Posts: 24
Allison shift window with Pac Brake on:

Brett, I was able to check this today on our first trip since I posted this question. The Pac Brake worked properly today and I saw that the Allison shift window changed to "4" when the brake activated. So all is good with the exhaust brake today.

The original problem of the Pac Brake not activating when switched on is still a mystery. It has only occurred twice in over a year of driving. I will revisit this question if/when it happens again, and consider replacing the throttle switch you mentioned earlier.

Michael
2001 Alpine Coach 36FDDS
Bellevue, WA
__________________
mbweitz is offline   Reply With Quote
Old 12-06-2015, 09:05 PM   #12
Senior Member
 
Join Date: Oct 2014
Posts: 523
Michael,

Though there could be a number of "failure points" the first suspect is a throttle position sensor.

Unless the "throttle closed" signal is received, the transmission will not downshift/exhaust brake will not activate.

Brett
2003 Alpine 38FDDS
__________________

__________________
wolfe10 is offline   Reply With Quote
Reply

Tags
brake



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Toad Brake light Question LongDogRanch Toads and Motorhome Related Towing 13 04-10-2015 09:18 AM
Exhaust Brake, Compression Brake, vs Turbo Brake dengraham Cummins Engines 15 09-28-2014 04:17 PM
Brakes ?? Bulldog74 Ford Motorhome Chassis Forum 7 07-07-2014 11:32 AM
Reprogramming the Jake Brake Rich-n-Linda Class A Motorhome Discussions 15 04-08-2014 10:23 PM
Newbie pac brake question BCCanuk Monaco Owner's Forum 13 02-08-2014 11:03 AM

» Virginia Campgrounds

Reviews provided by


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 05:44 AM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.