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philip potter
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, February 24, 2005 - 10:58 pm: | |
We are about to finnish putting a 6v92 and 748 Allison into my MC8.
Somehow, when a project takes me 8 months or so, I tend to forget things... things I maybe never knew, but can't remember if I never knew them.
Here are my questions.
1.The wireing that comes from the trans to the front of the bus splits 3 ways up front.
a. to the shifting box.
b. to an unkown plug that looks like the other end that hooks to the trans. Was this for an electronic accelorator? Is there such a thing? I hope it was only needed in the old bus it came from, because I have no where to go with it.
c. to a wire that hooks up power. Is this thing 12 or 24 volt? any hints on hooking it up to power?
2. This has to do with the wiring that hooks up to the trans.
a.It has the main connector that hooks up to the trans.
b.There is a split off that has two wires that I think connect to a speed sensor just before where the drive shaft connects. (I'm assuming I will not use this as my bus has an old fashion cable speedometer)
c.Then there is a split off that goes to a sensor/control unit that has a cable that runs up and connects to the throttle. This cable is set up so that it can not push on the throttle, but the cable (to this sending/contol unit) is pulled when the throttle is increased. What is this thing? We had to change and put on the throttle assembly from my old 8v71 to match my throttle linkage on the bus. The engine came with some kinkd of electronic/ air throttle that we took off. Will I need to hook this unit up to sync the trans with the throttle? Or does it have something to do with the old throttle system?
3.The trans has a trans cooler on one side. It is hooked up, with hoses, to 2 ports that are located on that side of the trans. One on the upper, and one on the lower part of the trans in the area of the bell housing. The other side of the trans has 2 more ports just like them that are open, waiting for me to hook something up to them. Only problem, I don't know what they are for. Help.
Any help is greatly appreciated. My family would like a bus that moved. |
Sean Welsh (Sean)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, February 25, 2005 - 12:03 am: | |
Phil,
I have a 748, so I will help as best I can.
Re #1. The 748 is an "ATEC" transmision (Allison Transmission Electronic Controls). The ATEC unit is a separate box, about the size of a cigar box, brown in color. The transmission will not work without it. The ATEC harness connects to the transmission itself, to the ATEC box, to the shift control (which is either a pushbutton keypad or a lever-type, depending on original customer order), and to the engine control computer if present. (You did not say whether your 92 series is a DDEC or not.)
Also, there are a number of wires in the harness that go to lights or switches on the dash. One is for a "check transmission" light, another is for the button that makes said light flash out the trouble codes, yet another is for the backup lights. There is also an output for the neutral safety, which should be interlocked with the starter circuit. Numbers for all these wires are printed on the wire jackets themselves every few inches. Somewhere, I have the circuit numbers for all these items if you need me to look them up. Most of these are grounding signals, so you will need relays to make them do what you need.
The ATEC requires a constant +12v source (on even when the bus is shut down). Since the MC8 is a 24v coach, you will need to supply the +12v from the battery center tap. Certain control inputs and outputs are also 12 volts, so there are relays in your future.
Lastly, there is a diagnostic connector that also mounts under the dash, which is where a technician can plug in the magic little reader they use to read codes and set parameters in the ATEC.
Re #2b. There is a place for a direct-drive speedo take-off, which often has a little generator attached, which is wired to drive an electric speedo. I believe you will need to remove the sender to connect your mechanical unit, but you really ought to consider getting an electric one if the tranny has the sender for it. They can be had for less than $50 and are easily reprogrammed if you change ratios or tire diameters.
Re #2c. The ATEC requires a throttle position sensor. If you have a DDEC engine, the throttle is just a pedal connected to a variable resistor, which informs the DDEC, and the ATEC gets throttle information from the DDEC. If, on the other hand, you have a mechanically governed engine, the throttle position sensor needs to be connected either to the mechanical throttle linkage, or to the air throttle linkage if so equipped. The ATEC requires this information to determine shift points.
Re #3. If I remember correctly, the 748 has an external transmission filter. One set of ports goes to the cooler, and one sets goes to the filter. I'd have to crawl underneath to see how mine is plumbed.
Allison has the 700 series owner/operator manual on its web site in PDF format, by the way, which you should download if you haven't already.
HTH,
-Sean |
philip potter
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, February 25, 2005 - 8:43 am: | |
Thanks Sean,
1.I do have the "cigar box" ATEC unit that connects in the middle of my harness.
2. I have no engine control computer. I did not think the 6v92 was a DDEC. I've never been around one. How do I know? What is the difference?
3. I assume the diagnostic connector is the smallest rectangle shaped black plug at the end of one of the "up front" leads. Would it make sense that the large round plug (that is the same size as the one that hooks up back at the trans) would be the wires that contain the dash switches and lights. I will open it up and look for printing on the wires today. Please explain, to my electronically challenged mind, the "grounding signals and relays to make them work". Also, if you have the circut numbers, will that help me know where to hook the wires up to my MC8?
4."ATEC constant 12v source" - I believe I have some 12 volt spots on my control pannel on the left of the driver's seat. Can I hook it up to one of them? What is the "battery center tap"? How do relays fit into this picture? This draws power all the time, until I pull the main shut off?
5. getting the electric speedo sounds like good advice. Where do I buy one? What more is there beyond finding the 2 wires in the harness up front that go to it?
6. I have never seen an air throttle linkage before, but I think that is what we removed to put on my mechanical linkage. It had a few air controlled rods connected to the throttle. Does that make sense? I believe I have a mechanically governed engine. So I should mount the throttle position sensor to work in the same way it did on the air contolled throttle system. It was just set up to be pulled as the throttle increases. It has an adjusting nut on the end of it. How will I know when it is adjusted right?
7. Any more info. on the external transmission filter. I don't have one. Where do I go for this?
I do have an Allison "HT - HTB 700 Electronic Control Series" Service Manual. I didn't find a wiring schematic.
phil |
tn bobs bus
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, February 25, 2005 - 9:10 am: | |
i have a 748, i would like to put in 1966 eagle 01 where can i get a wireing harness? |
James Maxwell (Jmaxwell)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, February 25, 2005 - 11:51 am: | |
Phil: Pls. take this as a well-intentioned suggestion meant to possibly save u money. You're questions and responses to Sean's given answers leads me to believe that u are into a project way over you're head that you have done very little research into. I am suggesting that you either enlist or hire someone who has some knowledge on this project before you do some serious damage to an ATEC control unit, which will cost u dearly.
Most late model 6v92s are DDEC and the control unit is mounted on top of the engine, front. A rectangular box about 6x8x3"high w/approx. 3 harness connectors on the side of it. The same caution applies to possible damage to this unit. If ure trans and eng both came from the same donor then most likely the engine is DDEC. FWIW |
philip potter
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, February 25, 2005 - 12:57 pm: | |
The engine and trans came together. The person I purchased it from was going to help with the wiring questions but he is very ill and I don't know if he will be able to respond. It is a mechanically governed engine. It does not have a control box with 3 harness connectors.
I don't claim to know much and have no intention of doing more than grunt work on this job myself. I have a mechanic doing the work that has been a tractor/deisel mechanic for 40 years and has rebuilt and worked on 6v92's (he just finnished a 6v92 out of frame rebuild on a MC9) as well as most other truck or tractor engines old and new alike. He, however, has never worked on a ATEC transmission before. Electrical systems are not one of his strengths. So I'm trying to help fill in the blanks. |
Sean Welsh (Sean)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, February 25, 2005 - 1:13 pm: | |
"2. I have no engine control computer. I did not think the 6v92 was a DDEC. I've never been around one. How do I know? What is the difference? "
As James wrote, many 6v92s are DDEC. There will be, as he says, a rectangular box with the connectors on it. Most likely, the factory paint on this engine will be silver. If the factory paint is green, you likeley have a mechanical model. The mechanical model has a "rack" to mechanically operate the injectors. I have only a passing familiarity with the mechanical ones -- you'll need to consult someone with real experience.
"3. I assume the diagnostic connector is the smallest rectangle shaped black plug at the end of one of the "up front" leads. Would it make sense that the large round plug (that is the same size as the one that hooks up back at the trans) would be the wires that contain the dash switches and lights. I will open it up and look for printing on the wires today. Please explain, to my electronically challenged mind, the "grounding signals and relays to make them work". Also, if you have the circut numbers, will that help me know where to hook the wires up to my MC8? "
Yes, the diag plug is rectangular, with, I think, 12 positions (not all of which will have wires in them).
Usually, the shift selector has a round canon-type plug on it, perhaps this is your mystery connector?
As for the relays, I will give you an example. There is a low-current grounding signal that indicates the transmission is in neutral. You will need a relay (12v or 24v) where one side of the coil goes to positive voltage, and the other connects to this signal. Through the N/O contacts of this relay you should run your (primary) starter circuit, so that the engine can only be started in Neutral.
Another example: The ATEC requires a +12v input when the "ignition" is "on." On your 24v system, you will need a 24v relay connected to your master switch, and then run a 12v source through the contacts to supply 12v power to the ATEC.
"4."ATEC constant 12v source" - I believe I have some 12 volt spots on my control pannel on the left of the driver's seat. Can I hook it up to one of them? What is the "battery center tap"? How do relays fit into this picture? This draws power all the time, until I pull the main shut off? "
The reason for the constant source is that the memory in the ATEC is an older type that needs power all the time. If you interrupt this power, the ATEC will lose any diagnostic codes it has stored, and also lose anything it's "learned" about the current driving environment. Not a crisis, but not ideal either. So one of the power inputs should go directly to the 12 side of the battery (through an appropriate sized fuse). The other input tells the ATEC to turn on and off, and that one goes to a switched 12v source as described above.
Yes, the ATEC draws power all the time, but it is just a miniscule amount to keep the memory alive.
When you say you have 12 volts under the dash, you can use this, but only if you fully understand how it is generated, how it is fused, and what else might be connected there. If that runs, say, your headlights, and a headlight causes the fuse or breaker to open while underway, interrupting power to the ATEC, you would be in a world of trouble. Main power to the ATEC must be separately fused.
The "center tap" refers to the point between the two 12volt batteries that are in series providing 24 volts to your coach.
"5. getting the electric speedo sounds like good advice. Where do I buy one? What more is there beyond finding the 2 wires in the harness up front that go to it? "
Search the archives for sources. VDO makes, IMO, the best units, and many automotive supply houses can get you VDO gauges. Generally, they require a switched power input (some will work on 24v, and I suggest you get a 24v model to save yourself additional hassle) and the two wires from the speedo sender. The unit will come with instructions for calibrating it to your road speed.
"6. I have never seen an air throttle linkage before, but I think that is what we removed to put on my mechanical linkage. It had a few air controlled rods connected to the throttle. Does that make sense? I believe I have a mechanically governed engine. So I should mount the throttle position sensor to work in the same way it did on the air contolled throttle system. It was just set up to be pulled as the throttle increases. It has an adjusting nut on the end of it. How will I know when it is adjusted right? "
I can't really help much here -- my engine is a DDEC. But, yes, the sender needs to connect to the linkage in such a way that it can read the exact position of the throttle anywhere in its operating range. As for adjustment, I suggest you have an Allison dealer do this (they will make field calls) as they will have the little plug-in reader to see what the sender is putting out, etc.
"7. Any more info. on the external transmission filter. I don't have one. Where do I go for this?"
It looks like an oil or fuel filter. Any Allison dealer should be able to provide it.
While you are at Allison, I suggest you also spring for the installation manual, which should spell all this out, and will have all the circuit numbers you need as well. Or, as Jim suggests, find someone to help you who already has the documentation.
HTH,
-Sean |
philip potter
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, February 25, 2005 - 11:14 pm: | |
Thanks for your help in getting me going in the right direction.
Todays progress:
I have a throttle control sensor schematic to show how it should be hooked up.
The wires connecting to a trans. speed sensor is for the ECU (computer).
I've located where to get the external trans, filter.
The "mystery plug" (not to the shifter box or diognostic plug)up front must have been pluged into the dash of the old bus system for power etc. I have an electrical schematic for the HT 700 trans. So I will now get started on sorting out those wires up front.
I also have a HT 700 Mechanic and parts man that is setting me up with info and parts. |
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