| Author |
Message |
TOM SHALLOW (Tvdad)
Registered Member
Username: Tvdad
Post Number: 7
Registered: 10-2006
Posted From: 66.31.82.33
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, June 19, 2007 - 5:58 pm: | |
I am the person with The don't shift light problem. It has been determined that the ATEC or ECU is bad. Does anyone have or know someone who has an ATEC for the HT 748 the part number appears to be 29502534 Nimco doen't appear to have that part number. |
JR Lynch (Njt5047)
Registered Member
Username: Njt5047
Post Number: 167
Registered: 7-2006
Posted From: 69.132.237.9
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, June 19, 2007 - 11:24 pm: | |
Have you tried US Coach? Phone is 856-767-4848
Ask for Mike.
I'd be interested in how a determination was made that either the ATEC or DDEC ECU is bad.
Myriad simple failures will cause the "do not shift" light to come on. An ATEC ECM failure is way too rare. Still, it may be screwed.
I'd be checking the unit with a ProLink and appropriate card before buying ECMs.
Wiring issues, touch pad issues, engine ECM com links or faults will all set the "do not shift" light. As will hard-core transmission failure, which is not that uncommon.
You may find that other ATEC controllers will work without problems. Buses with HT748s are scrapped out regularly by Nimco...may be some variation from what you have, yet would work OK.
Any "T" drive DDEC II/ATEC controller may work, albeit with some variation in shift points.
Failed ECMs, DDEC or ATEC, are almost unheard of...unless a shadetree mechanic attempts to diagnose the system and damages it during the process.
Perhaps you could contact an Allison dealer (I know, far fetched) and inquire as to what ATEC ECMs may be interchangeable, and what outcome could be expected.
I'd be interested in what resolves your problem.
Best, JR |
larry currier (Larryc)
Registered Member
Username: Larryc
Post Number: 131
Registered: 2-2007
Posted From: 205.188.116.8
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, June 20, 2007 - 12:16 am: | |
Tom, I'm sure I posted the name of a rebuilder/parts whse for DDEC/ATEC in Mn. Now is the time to call them and save some money. |
niles steckbauer (Niles500)
Registered Member
Username: Niles500
Post Number: 743
Registered: 11-2004
Posted From: 72.91.107.56
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, June 20, 2007 - 12:56 am: | |
Tom - don't think I'm crazy - BUT - before everyone tells you I AM - disconnect your ATEC, DDEC from its power source for a 10 minute perod and "cold start" it to see if you still have a "no shift" indicator - I'm bound to get flamed for this but - HTH |
Sean Welsh (Sean)
Registered Member
Username: Sean
Post Number: 564
Registered: 1-2003
Posted From: 67.142.130.28
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, June 20, 2007 - 4:54 pm: | |
"I'd be checking the unit with a ProLink and appropriate card before buying ECMs"
There is no cartridge for the ProLink that supports Allison CEC1. You need the Dedicated Reader tool. Sorry.
I've advised Tom in this same thread on the other board to take the ECM to Allison to have it diagnosed.
If it's bad, you can't just find another one and swap it in... you need to have the ROMs programmed. IIRC, you can't move the ROMs from the old one, either, because the serial number is embedded.
FWIW.
-Sean
http://OurOdyssey.BlogSpot.com |
JR Lynch (Njt5047)
Registered Member
Username: Njt5047
Post Number: 169
Registered: 7-2006
Posted From: 69.132.237.9
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, June 20, 2007 - 9:35 pm: | |
Bummer. Allison don't make it easy!
I've had the "do not shift" lite come on twice.
Both times it was related to the DDEC unit and not the ATEC.
Would it be possible to swap a DDEC II unit and ATEC ECM from the same donor coach? Matched units that recognize each other? As long as the donor has similar engine/trans/drive ratios, ???
Does the transmission have any code storage components?
Are there any other DDEC/ATEC components on the coach (other than the DDEC and ATEC ECMs) that store code?
I don't mean to beat this thing, but I've got an ATEC HT748 and may face the same problems in the future.
Good Luck with sorting out the system, JR |
TOM SHALLOW (Tvdad)
Registered Member
Username: Tvdad
Post Number: 8
Registered: 10-2006
Posted From: 66.31.82.33
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, June 20, 2007 - 10:33 pm: | |
The Allison Daler is the one that determined that he felt that the ATEC was bad HE CLAIMS THAT HE COULD SEE THE COMPUTER GOING FROM D TO N TO R THAT IS WHAT CONVINCED HIM THE ECU WAS BAD |
JR Lynch (Njt5047)
Registered Member
Username: Njt5047
Post Number: 170
Registered: 7-2006
Posted From: 69.132.237.9
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, June 21, 2007 - 11:09 pm: | |
I was discussing your issue with a retired Mecklenburg County mechanic today. He indicates that they still have a few HT748 transmissions and that they changed transmissions out without any programming. They didn't like the DDEC systems at all, but, they were generally dependable. They had a bad time diagnosing failures.
This takes me back to my original thought, have you considerd locating a used ATEC ECM from a similarly equipped bus (DDEC II, same engine/same trans/same rear drive ratios) and trying it. It would be much less expensive. May not work either. The worse that would happen is that the ECM isn't the problem. There's nothing that I see in the bus (I'm looking at MCIs, not Neoplan?? Sean?) or the engine that's specifically programmed to work with specific ECM.
As long as the engines are the same, the ECM should be interchangeable. The ATEC ECM may look for the same engine ECM, but installing both units would resolve this issue. You may end up with a different road speed limiter, cruise may or may not be enabled, shift points may be slightly varied, but IF the ATEC ECM has failed, you may wish to try it before you spend $4K on another new ECM...a unit that probably could not be returned should it prove to not be your problem.
Did you take the bus, or just the ATEC ECM to the Allison dealer? I'll assume just the ATEC ECM.
Another thingy, is why did the ATEC unit fail? If indeed it has failed? That would be interesting to install another unit and have the same sort of issues. Is the trans shift harness available for inspection in a Neoplan? The shift pad and/or wiring harness may have issues.
Sean, other than performance characteristics, what would stop one from installing another functional ATEC ECM? In a '89/90 Neoplan, are there any other components that communicate with the ECM and ATEC unit that are programmed to operate only with the OEM installed ECMs?
JR |
Sean Welsh (Sean)
Registered Member
Username: Sean
Post Number: 565
Registered: 1-2003
Posted From: 67.142.130.44
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, June 22, 2007 - 3:43 am: | |
The DDEC and ATEC operate in cooperation with each other through an interface. Improper ATEC programming will cause rough shifts and may even result in wheel slip and/or lockup.
There is no reason not to at least try another ECM, if available. It may get the coach going enough to move the process along. Also, if the original ECM is shot, there is no harm in at least trying to move the ROMs over into a different ECM. If it works, that will effectively reprogram the replacement ECM to the original spec.
The other components which communicate with the ECM and depend on proper programming are the shifter (for example, pushbutton vs. lever style), retarder switch (if any), neutral safety interlock, and a handful of other coach-interface relays.
As to why it failed: ATEC ECMs are very robust, but there is a long list of no-no's that will instantly fry them. For example, putting 12v (or worse, 24v) direct to any number of signal pins that provide grounding-type outputs from the ECM. There is a clear warning on each of these in the CEC diagnostic guide, stating that immediate and irreparable ECM damage will result from this.
All it takes is to inadvertently connect the wrong relay terminal to one of these pins from, say, the backup-light relay or the neutral-safety relay, and the ECM is history.
FWIW.
BTW, if the ECM needs to be replaced, I definitely recommend you buy the CEC1 troubleshooting manual, and check every harness pin before hooking up the replacement ECM.
-Sean
http://OurOdyssey.BlogSpot.com |
TOM SHALLOW (Tvdad)
Registered Member
Username: Tvdad
Post Number: 9
Registered: 10-2006
Posted From: 66.31.82.33
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, June 22, 2007 - 6:12 pm: | |
Sean
I think that you have aced the problem there was a short in the braking circuit that I repaired but after the dont shift light came on. I was told by an ex neoplan empolyee that this problem would not cause this problem sounds as though he was wrong. Thanks for the help. I did order a used ATEC from NIMCO and plan on chaning the EPROM
TVDAD |
|