Author Topic: Allison Elictrical Issue  (Read 1715 times)

Richard Davis

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Allison Elictrical Issue
« on: October 11, 2021, 06:02:38 PM »
This is chapter two.  I started a new topic since this is secondary to my original problem.  Many of you followed my thread over the last two weeks as I diagnosed and replaced an injector on my C9 in a 2006 Monterey Ventura IV.  We continued on our trip home yesterday and the C9 ran flawlessly, but we did not get far until another problem popped up.  I am getting a diagnostic code 3500 from the Allison.  It is intermittently losing electrical connection from the battery to the ECU and/or VIM.  I "assume" that while working on the engine over the last two weeks, I have disturbed a connection to the transmission.  Dave Atherton has sent me the troubleshooting information from the Allison manual, however I kind of need to know where these components are located on my coach.  So, if any of you have been down this road before and can tell me where to look for things, I would appreciate it.  The Allison ECU is supposed to have direct 12 volt positive and negative connection to the battery.  Therefor I assume one of those white wires attached to the starting battery is the ECU ground.  Does anyone know how to identify which one.  And, do you know specifically where the Allison ECU gets its 12 volt positive power supply.  Any assistance you can provide me is greatly appreciated since I am again stuck in a RV park far from home (Clayton, NM.).  Thanks!
Richard
06 Monterey Ventura IV, C9 400 hp

Steve Huber Co-Admin

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Re: Allison Elictrical Issue
« Reply #1 on: October 11, 2021, 11:02:48 PM »
Steve
2015-          07 Contessa Bayshore C9,  400 hp
2013-2015: 00 Marquis Tourmaline, C12, 425 hp
2005-2013: 01 Contessa Naples, 3126B, 330 hp

Richard Davis

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Re: Allison Elictrical Issue
« Reply #2 on: October 13, 2021, 01:05:11 AM »
Gentlemen
I feel like I am chasing my tail and getting nowhere.  (If any of you need to know where the Allison ECU and VIM are located on a 2006 Monterey, they are attached to the back wall inside the kick plate to the left of the drivers knees, directly under the shift pad.)  I have verified positive and negative 12 volt continuity from the incoming VIM cable through to the ECU.  Everything checks out correctly.  But as soon as I try to move the coach, I get a few hundred yards and as soon as the coach rocks a little, the transmission bucks and sets a diagnosis code 3500 (failed 12 volt power).  I have checked and cleaned and tightened all the connections that I think might be relevant.  No joy.  Does anyone know exactly where the Allison VIM gets its 12 volt power.  It is not powered via the FRB (Front Run Bay).  Its power comes from the chassis battery somewhere after the battery disconnect switch, but I have not been able to determine exactly where.  This issue acts like a failing automatic circuit breaker that loses power, but immediately resets.  If anyone has insight to this situation please chime in.
Richard         
06 Monterey Ventura IV, C9 400 hp

Eric Maclean

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Re: Allison Elictrical Issue
« Reply #3 on: October 13, 2021, 01:46:34 AM »
Richard
Check in or near the battery compartment there should be at least 2 small inline ATO fuse holders one for the engine ECM and one for the TCM these are direct 12 volt feeds that are not switched .
They are usually located along with the battery cables in the battery box which also lends them to corrosion

There should be a circuit breaker in the front run bay #22 marked xsmn  which is the switched ignition source to the transmission
TCM
The circuit breaker above that one is #21 engine ECM switched power.

As others have mentioned the ignition buss solenoid s are known to develop problems depending on which power you are loosing it could be in one of the two places I've discovered.

In the coach assist library there is an Allison automatic throubleshooting manual which will help you understand where the TCM power and grounds are feed to the TCM .

Remember to check the grounds as well .

Hope this helps
Eric
1997 Patriot Yorktown
3126-B
2009 Chevy HHR
Roadmaster falcon tow bar
Demco Air Force one tow brake.

Steve Huber Co-Admin

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Re: Allison Elictrical Issue
« Reply #4 on: October 13, 2021, 03:58:22 AM »
Richard,
In addition to Eric's suggestions, check/clean the connections in the wiring under the coach that runs to the tranny. They can be problematic and be affected by movement of the coach.
Steve
Steve
2015-          07 Contessa Bayshore C9,  400 hp
2013-2015: 00 Marquis Tourmaline, C12, 425 hp
2005-2013: 01 Contessa Naples, 3126B, 330 hp
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Richard Davis

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Re: Allison Elictrical Issue
« Reply #5 on: October 15, 2021, 02:52:44 AM »
Update
After 3 days chasing circuits with a digital multimeter, cleaning and tightening connections, I finally found where the Allison (and Alladin) gets its 12 volt power.  As Eric pointed out there are 2 fuses in the battery compartment that power the engine computers.  On my 2006 Monterey there is a third standard blade 20 amp fuse.  All three of these are mounted in a small rectangular box with plastic weather covers over the fuses (left wall of the battery box).  I chased the source to these fuses back around and into the electrical box where the Big Boy is installed.  There is a 35 amp ANL fuse bolted to the chassis battery bus.  The other end of the ANL fuse has a ring connector crimped to an 8 gauge wire that runs to that fuse box.  As I reached behind the Big Boy solenoid to check the connections, the wire came out of the crimp into my hand.  That improper crimp was done at the factory and has been a disaster waiting to happen for 16 years.  Evidently, opening and closing the battery tray last week while I worked to install a new injector wiggled that loose connection just enough that every time thereafter when I hit a bump, power was lost to the Allison VIM/ECU.  As a side benefit for me, my Alladin now stays powered correctly.  For the 5 years that I have owned this coach, my Alladin display would come and go.  I thought I had a failing control board on the Alladin, but I now realize that the problem all along was that bad connection to the battery bus.  I drove it 4 hours today, no problems.  I thank all of you for your assistance.  This forum is an invaluable resource.
Richard 
06 Monterey Ventura IV, C9 400 hp
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Eric Maclean

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Re: Allison Elictrical Issue
« Reply #6 on: October 15, 2021, 12:07:51 PM »
Richard
That's great news now you can Cruz without any more problems with a little luck. LOL.

Eric
1997 Patriot Yorktown
3126-B
2009 Chevy HHR
Roadmaster falcon tow bar
Demco Air Force one tow brake.