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Old 01-11-2019, 06:21 PM   #81
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Well turf, you are not the only one baffled. Unbelievable turnaround today, hope it holds up for you, touch wood!
That pic of the engine layout helps get oriented and the grid heater has to be in the air intake piping, which I think now is on the rh side of the block, higher up on the intake.

I did some reading on this and found there are 2 grid heaters in there. They draw some 90 amps a piece. The connections seem to be internal for power and ground and wiring appears to come froom front of engine and underneath to feed these. Relay melt downs seem very common and tend to melt enough that the contacts can't close at times. So, power is continuous it seems.

Use your block heater whenever you can before startup to reduce load on batteries and alternator.
Carry a spare alt for sure if possible in your situation.

You night want to start steaming thaat engine down. All that grime is power robbing and could be part of the problem.
Hope the trip goes well, keeping fingers crossed for you.
Safe travels.



John
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Old 01-11-2019, 07:29 PM   #82
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Try moving the big wire back against the oil filter and see if the problem comes back. I've seen spark plug wires with apparently good insulation arching like mad.



My guess is that one of the wires you moved did the trick. The big cable may have bad insulation or be all corroded inside the insulation or maybe the small alternator wire may have been getting intermittent contact with the alt and shutting down the field current giving a no charge condition.



I'd definitely want to have a good look at both wires to see for sure which one was the problem, or to to verify that both are fine and that some other intermittent problem still exists. I hate problems that just randomly disappear because you never know when they'll come back.
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Old 01-11-2019, 08:53 PM   #83
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Quote:
Originally Posted by BlackJohn View Post
Well turf, you are not the only one baffled. Unbelievable turnaround today, hope it holds up for you, touch wood!
That pic of the engine layout helps get oriented and the grid heater has to be in the air intake piping, which I think now is on the rh side of the block, higher up on the intake.

I did some reading on this and found there are 2 grid heaters in there. They draw some 90 amps a piece. The connections seem to be internal for power and ground and wiring appears to come froom front of engine and underneath to feed these. Relay melt downs seem very common and tend to melt enough that the contacts can't close at times. So, power is continuous it seems.

Use your block heater whenever you can before startup to reduce load on batteries and alternator.
Carry a spare alt for sure if possible in your situation.

You night want to start steaming thaat engine down. All that grime is power robbing and could be part of the problem.
Hope the trip goes well, keeping fingers crossed for you.
Safe travels.



John
About the relays for the heaters this is what I had mentioned early in this post. The relays do have a habit of sticking. I have had this problem myself. It will be fine for a while then one day it will stick on and it does draw more then the alternator can put out. If the engine is turned off while it is still stuck on (the heater relay) then it will run the batteries down quickly.

If it where mine I would be aware of this, but also the moveing of wire away from the oil filter may well be the real issue. Time will tell. At least at this point he will have a better understanding of electrical on the bus, and hopefully if it comes up again he can get right into it.
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Old 01-12-2019, 12:39 AM   #84
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i appreciate the trouble shooting.

this gremlin has been plaguing me for a year-ish. i only driven it a few miles a week and sometimes it works, and sometimes it doesn't. the the skoolie trip got me motivated to look into it... hoping to solve it.

last summer, i got a signal tracer to try and locate the short, but never had luck locating a fault. i know its a short, but booyahs' comments of it being a big short kind of narrow it down to the starter, heater relays..etc.

maybe my starter install is incorrect. maybe the solenoid is sticky?

as i find out more, i will update the post.

if anyone comes across an electrical for a 93 BB TCFE, it would be interesting.

my house batteries are due for replacement, so i am sure to be purchasing some batteries soon for sure.

thanks
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Old 01-12-2019, 06:33 AM   #85
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Well turf, I suggest googling the 5-9 grid he heater for some knowledge about this gremlin. Look at the pics for the heaters and the heater relay.
After that the mud starts to clear.
First off, the heat causes the grids to carbon up after a while and either burn themselves up or just quit. Some just remove them totally and use the block heater. I guess it depends on ambient temp at your location.


The biggest issue is the heater relay on these engines. every electrical component has only so many useful uses over its lifetime. Something like our hearts, some get many years use, some get fewer if not used properly or defective.
Looking at the heater relay, there are 2 power connections for #2 wire, a 100 amp conductor. One for each heater grid. Built in one block but separated electrically. The construction internally of these is a couple of coils, a couple of heavy springs and a couple of carbon contactors, like the stuff brushes are made of.

These carbon pieces with heat over time get pitted and spew carbon dust into the barrels the springs work in. This jams the working movements of both sides and will create just what you have happening.

I would be changing those pronto if me. Then the grid heaters too or at least open and take a look.


So, pretty sure your alt is well and cables for now are ok.



In this discussion, we tried to think of any and every possibility but the above we did not touch. To me this is the problem area, nothing else and would start working on it if you make it to warmer climes.

Or, just pull the fuses for the heater relays and go block heater all the way, meaning below 40f most likely.


I wish you good luck man and have to say this was a brain teaser for sure. Toughest one I have run across.


John
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Old 01-13-2019, 07:32 PM   #86
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I am jumping into this discussion at the end so I don't know how helpful any comments I have will be for you.


I have seen a LOT of school buses with the Cummins 6BT engine. I don't recall ever seeing any of them with a intake heater like the 6BT used in a Dodge truck. That isn't saying that all school buses don't have intake heaters. I just have never seen one so equipped. But then every school bus I have seen that has had the 6BT also had a 110-VAC engine heater.


Whatever is draining your juice is doing so in very large amounts. Wherever it is going it will be getting very warm, if not very hot. If might be easier to find where your juice is leaking not with an electrical meter but with an infrared thermometer. Once you find a hot spot it might then be easier to find where the juice is leaking with an electrical meter.


I would also think that if moving some wires stopped the problem I would try moving them back to see if the problem came back. If that were the case it would sure reduce the area for the hunt for leaking juice.


I would agree with the thinking that if you have been leaking juice out of those wires then it would probably be a good idea to replace the those wires. Repeated heating and cooling of electrical wires greatly reduces the conductivity of wire. Even if it no longer is leaking juice it won't carry the same load it did when new. Which can cause new problems down the road.


I hope the only progress you share is that you no longer have that problem.

Good Luck and Happy Trails on your trip.
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Old 01-19-2019, 08:41 PM   #87
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i replaced my batteries and problems seems gone.

just made a 1600 mile trip. started like a charm every time.

if some one wants to tell me "its the batteries" go right ahead.





thanks for the help and support
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Old 01-20-2019, 07:35 AM   #88
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Turf, lots of mentions about a grid heater, but your bus for sure doesn't have one. Neither does mine, it's also a 12v cumming 5.9 in a TC2000FE. My understanding is that most of these won't have it.

Sounds like you've got the problem fixed but in case you have trouble in the future you cut down a lot of diagnostics if you already can rule out a non-existent grid/glow system!

Here's the electrical diagram for a slightly newer TC2000.. Should be pretty much the same for yours. https://wanderlounge.net/1996-tc2000-wiring-diagram/


Happy trails!
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Old 01-20-2019, 07:52 AM   #89
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From post #1, " the batteries are dated 3/15." Almost four years.



Always suspect and eliminate the easiest things first. Glad the new ones made your trip go well but your bus still needs a lot of work to be in top shape.



For three alternators to fail was reason enough to go to a shop for a battery test, so do whatever you have to do to maintain the new ones, even under warranty.


John
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Old 02-27-2019, 08:46 PM   #90
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hey again!!

it's back. my short.

new batteries a month ago solved the problem, but the gremlin is back.

i started the bus fine 2 days ago and it ran fine. i parked the bus a few feet off its spot so when i tried to start back up and move, my battery meter went blank, no starter, nothing.

today i tried to start the bus and i get 2 different results.
1st result is when the key is on, the air alarm beeps, everything seems fine, and the starter just clicks.
the second result is the volt meter goes blank, and nothing from the starter. when the key is turned off, the display on the battery meter comes back on.

the battery charger shows a higher voltage than the battery meter. im begining to wonder if my battery shunt or battery idolater may be the issue here. i just don't see what or where the short is.

any short tracking advice appreciated!

Dave
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