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Old 12-30-2017, 01:51 PM   #441
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wait... you were running a 1500 watt heater full time while driving?
-Christopher

Yes, but I now realize that the behavior started sometime before that. Actually I can't find a listed wattage on the heater. It is just one of those little ones. I plan to replumb the coolant heater but haven't yet.



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Old 12-30-2017, 01:53 PM   #442
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[QUOTE=cadillackid;241859

so the regulator could be breakering out under the heavy load.. then kicks back in, then kicks out again... 1500 watt heater after you factor inverter losses, wiring losses, and the like is going to be loading the alternator with more than that...
-Christopher[/QUOTE]


This happens with no load other than what the ecm is activating.


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Old 12-30-2017, 01:57 PM   #443
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Seems to me that the ECM is doing its job correctly and demanding that the heating come on in regular intervals at low idle for optimum combustion.

In my mind that engine is doing what it should be if what you say is a regular pattern happening.
Any engine is designed to run at a certain temp for overall health so all these systems are vital and mostly they are pretty bulletproof in that respect.

John

Maybe. And it is possible it has been happening for a long time without me noticing. The other gauges quit working though, so that seems weird.



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Old 12-30-2017, 02:00 PM   #444
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Most owners do not understand what they have when they buy a diesel anything and for lack of understanding are their own worst enemy. Cool down is a important as warmup too. You don't just shut off a hot diesel without a few minutes idling it down to cool. Short grocery or coffee runs come to mind. They never truly warm up so that's when troubles occur.
If one thinks they will have a long running trouble free engine, they better get an education in diesel101 quickly.
Is your intake heating done by grid or glowplugs?

John

I have owned diesel before, but this is a lot different than my diesel truck was. It uses an intake heater instead of plugs. That seems to be working fine.



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Old 12-30-2017, 02:20 PM   #445
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Finally metered at the batts. 12.8 with engine off, 14.1 at idle. No fluctuation regardless of what the dash says.


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Old 12-30-2017, 03:01 PM   #446
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so i wonder iof thomas does the same thing navistar does and that is the main gauges are actually a J708 (or J1939) comms link to the ECM.. on my red bus if that comms link glitches.. (and it does).. then the 5 main gauges stop reading (volts, rpm, mph, oil P, temp).. I know the 3126 is a HEUI engine so maybe the dash is losing comms? defaults to 0?

-Christopher
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Old 12-30-2017, 03:20 PM   #447
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I have owned diesel before, but this is a lot different than my diesel truck was. It uses an intake heater instead of plugs. That seems to be working fine.



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Sorry if you took offense to the "new to diesels," wasn't directed at you at all but for the benefit of all reading. There are many differences in the operation depending on the climate so basics are a must without sayinn.

I would trust meter readings more than idiot guages so I still think yours is running just fine but better plumb that heater in quick.

John
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Old 12-30-2017, 07:54 PM   #448
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Well the guages have quit altogether now...


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Old 12-30-2017, 07:59 PM   #449
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Well the guages have quit altogether now...


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I'm leaning towards something expensive and blown in the cluster, or bad grounds.

Either way, the numbers you put up show the alternator doing its job and the batteries with decent voltage.

It might be worth measuring the battery voltage again with that heater running, but probably not helpful if the gauges have quit without it running.
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Old 12-31-2017, 09:16 AM   #450
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Well I made it home to Chattanooga from Knoxville. For the first 30 minutes of the trip the instruments would intermittently work and then go out. It seems like the oil pressure and water temperature are on the same bus as the voltage and the tachometer and speedometer are on a separate bus. But all of them eventually quit working entirely about 30 minutes into the drive. When the tachometer and speedometer readouts quit working it seems like the transmission quit getting data on RPM and speed because the shift schedule would change and although I was still able to go highway speeds I donít think I had six gear available. I just parked it at 55 and it made it home without trouble but I was worried that I was going to blow something up in the transmission. Thankfully that didnít happen.


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Old 12-31-2017, 09:22 AM   #451
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Speed based on gps.


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Old 12-31-2017, 09:31 AM   #452
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so it sounds to me like something is shorting out or opening up the J1939 bus. the transmission gets data from the ECM via J1939. (assuming you have a 2000 series or MD3060)..and im thinking your gauge pod does too.. its a bus type system so each device is connected in parallel for communications.. its a 3 wire system with one wire being ground.. the other 2 arew CAN high and CAN low..

I dont know caterpillar so I cant tell you where to look for the wires.. however if the gauge panel is going bad. it could pull down one of the lines and fail the trans comms out.. (most allisons will light up the check trans light if the J1939 goes down)..

when the J1939 link goes down the allison will unlock the torque converter (which feels like you are missing a gear).. during unlocked operation it estimates your throttle input by looking at torque cionverter speed vs turbine speed so it can still operate with some accuracy for sdhift points and shift quality.. normally your throttle position and engine load data are sent across the J1939 interface so it doesnt need to estimate.. its not quite a limp-home mode but is a fail-safe mode where you can still reach higher speeds than limp mode which is 2nd gear forever..

im not sure if you can contact thomas to get a copy of the wiring diagrams to see about troubleshooting that interface link? all of my diagrams are navistar. a good start would be just checking all of the wiring connectors that plug into your engine and trans computers to make sure they are good and tight.. and not over-torqued..

J1939 is a modified RS485 at the physical layer so its generally pretty resilient but loose connections or a short across or to ground from either wire will result in issues..

often times the wires for J1939 are twisted (2 of them) (ground will be separate).. so it may be easy to spot the wires in the harness as being a twisted pair of wires..
-Christopher
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Old 12-31-2017, 10:45 AM   #453
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David, I have wiring diagrams for the Saf-T-Liner with the CAT 3126, if you need them.

Send me a message and I'll email them to you
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Old 12-31-2017, 11:08 AM   #454
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Better yet ... In case you haven't found this.

All of the info is at this link:

https://drive.google.com/drive/u/0/f...1lTandWYmFRaVk

The documents are a mixture. Most seem to refer to the 98/99 model year although a couple are for the C2.

However, CAT went electronic much earlier than Cummins, so the engine wiring diagrams should apply.
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Old 12-31-2017, 12:55 PM   #455
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Okay, We've been working for a couple of weeks and I figured it was finally time to start a thread! The bus is a 2001 Thomas Saf-T-Liner. It is 36' long bumper to bumper and has a rear engine layout. It has conventional springs but rides nicely, I think due in part to the rear engine design. It has the CAT 3126 (which is either the worst engine ever or the best of the early electronic engines, I feel like after researching that it is a decent engine unless until you have to have major work done by CAT, in which case it can be pricey to service), paired with the MD3060 transmission (which most people say is a great unit).

The general progress so far has been to
  1. Remove and recycle the seats
  2. Remove the cabin heater and lines
  3. Remove the rubber floor to discover no plywood only metal
  4. Discover that it is very hard to get the flooring cement off of the metal
  5. And finally, use a sandpaper flap brush on an angle grinder to get the cement off.

I've learned a few things so far:
  1. No matter what, this is just a lot of physical work.
  2. If something seems impossibly hard, you probably aren't approaching it the best way.
  3. Most of the things I've worried about haven't happened.

Finally, here are a list of things I really worried about when trying to decide to do the project/buy this bus:
  1. It would be difficult to drive a bus = not true.
  2. It would be difficult to get it registered = not true.
  3. It would be difficult to get insured = not true
  4. My neighbors would be upset and make me move it = not true
  5. It would not make it the 5 hr. drive home without a breakdown = not true
  6. The CAT engine would be a big mistake = jury is out.
  7. It would be quite difficult to do it on a minimal budget = almost certainly true.

If you are thinking of buying a bus please don't assume you will have the same experience, but thought it might be helpful to share mine.

So far the project has been a great way to collaborate with my daughters and wife in the design and work. It is fun to get to teach them how to use hand tools, and to see our combined effort result in such tangible progress.

Thanks for reading and I look forward to any comments and advice that you may have!
She's a beauty!

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Old 12-31-2017, 03:35 PM   #456
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so it sounds to me like something is shorting out or opening up the J1939 bus. the transmission gets data from the ECM via J1939. (assuming you have a 2000 series or MD3060)..and im thinking your gauge pod does too.. its a bus type system so each device is connected in parallel for communications.. its a 3 wire system with one wire being ground.. the other 2 arew CAN high and CAN low..

I dont know caterpillar so I cant tell you where to look for the wires.. however if the gauge panel is going bad. it could pull down one of the lines and fail the trans comms out.. (most allisons will light up the check trans light if the J1939 goes down)..

when the J1939 link goes down the allison will unlock the torque converter (which feels like you are missing a gear).. during unlocked operation it estimates your throttle input by looking at torque cionverter speed vs turbine speed so it can still operate with some accuracy for sdhift points and shift quality.. normally your throttle position and engine load data are sent across the J1939 interface so it doesnt need to estimate.. its not quite a limp-home mode but is a fail-safe mode where you can still reach higher speeds than limp mode which is 2nd gear forever..

im not sure if you can contact thomas to get a copy of the wiring diagrams to see about troubleshooting that interface link? all of my diagrams are navistar. a good start would be just checking all of the wiring connectors that plug into your engine and trans computers to make sure they are good and tight.. and not over-torqued..

J1939 is a modified RS485 at the physical layer so its generally pretty resilient but loose connections or a short across or to ground from either wire will result in issues..

often times the wires for J1939 are twisted (2 of them) (ground will be separate).. so it may be easy to spot the wires in the harness as being a twisted pair of wires..
-Christopher


I had to read this more than once and do a bunch of Google searching but I think you're right and I am much more educated on the architecture of the system! Thanks! Already found some suspicious things. Will post photos and more when I can.


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Old 12-31-2017, 03:37 PM   #457
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Better yet ... In case you haven't found this.



All of the info is at this link:



https://drive.google.com/drive/u/0/f...1lTandWYmFRaVk



The documents are a mixture. Most seem to refer to the 98/99 model year although a couple are for the C2.



However, CAT went electronic much earlier than Cummins, so the engine wiring diagrams should apply.


This is super helpful! Thank you! I can see where the problems likely are in the schematic. Now I just need to figure out what in all looks like in physical form!


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Old 12-31-2017, 04:35 PM   #458
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J1939 is a modified RS485 at the physical layer
-Christopher
THAT is interesting. Explains a few things.
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Old 12-31-2017, 04:56 PM   #459
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First picture is the main breaker and data panel to the right side of the engine in the rear compartment. The second picture is a close-up on the multi pin connectors going into the side. I believe there are two sets of twisted-pair with a separate bare wire ground. You may be able to see that the ground is completely broken. Itís so degraded that I think the ground was probably bad for a while and the system is probably just able to function because it was grounding in some other way. My guess is that if I can pull this off Iím gonna find that the insulated wires are no longer good even though they donít appear to be broken.


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Old 12-31-2017, 05:04 PM   #460
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Any advice on how to re-terminate this style of a connector? They didnít leave me a whole a lot of slack in the line which is I think partly responsible for whatís happened here.


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