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Old 08-22-2021, 10:46 PM   #61
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Engine: IC T444E / Allison MT643
Rated Cap: 72 Kids / 48 Adults
I found my 1997+ version of the diagnostic manual...yay!

The correct start sequence is:
Ignition switch to ACC (ECM does it's diagnostic check)
Neutral switch (likely suspect as it powers the crank relay)
Clutch switch (bypassed for automatics, which mine is, but if disconnected can cause a no crank)
Crank relay
Start relay
Starter solenoid

I'll keep looking, yet if anyone knows where my Neutral and clutch switches are located on my bus (2000 Amtran RE), I'd appreciate knowing.

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Old 08-28-2021, 08:38 PM   #62
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Update:

It turns out we found several issues. How the bus ever started, I'll never know.

The first issue was the accessories blade fuse blowing when I was driving it back from Yakima after it was "fixed".

Second, the interlock solenoid was not working. We decided to simply remove the wires leading to the solenoid in the front panel from the terminal block, then we combined the two wires in the cab, one from the front ignition switch, the other we're not sure where it goes, onto the same terminal on the block. This eliminates the Interlock system and gives us a direct connection.

Third, and we're not sure what the actual issue is, but we believe the ECM is the issue. The wire from the Neutral switch to the ECM tones, so does the wire from the ECM to the crank relay, yet we are not getting a signal from the ECM to the relay that grounds the coil. We removed the ground terminal from the relay socket and added one that is grounded. This allows the bus to start, yet in ANY GEAR. It's temporary.

What I'm not sure of is how to test the ECM to tell why it's not passing signals.

Anyone that can shed some light on this, please do.
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Old 08-28-2021, 08:53 PM   #63
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The neutral relay should be easy just take the computer out of the mix. You can have the neutral safety switch go between ground and the relay so when the trans is in N and the key is on the relay engages. (wire the +12 side of the coil to IGN source if it isn’t already) if the trans is in gear the relay willl turn off. Without the computer caring
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Old 08-28-2021, 09:53 PM   #64
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Quote:
Originally Posted by cadillackid View Post
The neutral relay should be easy just take the computer out of the mix. You can have the neutral safety switch go between ground and the relay so when the trans is in N and the key is on the relay engages. (wire the +12 side of the coil to IGN source if it isn’t already) if the trans is in gear the relay willl turn off. Without the computer caring
I like the idea, yet I think the problem is that the Neutral safety switch has 12v+ coming from the front ignition switch, then through the switch delivering 12v to the ECM. Upon recognizing the 12v at ECM, I believe the ECM Voltage Regulator turns it into a 5v signal and sends it to terminal 26, that in turns activates terminal 46 which turns on the ground at terminal 86 on the ECI relay.

So, placing the outgoing line of the Neutral safety switch between the ground and the relay would add 12+v to the ground terminal.

I could though add a relay between the outgoing 12v of the neutral switch that activates the ground wire.

My only concern with this is what if this ECM issue is a sign of the ECM failing?

Without an ECM, I've got bigger issues, so I want to see about how to test/fix/replace the ECM.
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Old 08-30-2021, 01:58 PM   #65
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UPDATE:

We added a relay between the hard ground wire and crank ground terminal. It works just fine, no start in gear, start in neutral.

Yet, after the fact, I thought it may not have been necessary because if the tranny is in gear, the neutral switch should not pass 12v, so the circuit isn't complete. Yes??

Our next step is to add the rear ignition switch. This has never worked and will be welcomed when it comes to troubleshooting we won't have to constantly go to the front ignition.

By removing the interlock system, the rear panel diodes and adding the rear ignition switch, it should make the mechanical/electrical systems more mechanical and simple to assure more reliability.
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Old 08-30-2021, 03:43 PM   #66
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Quote:
Originally Posted by Simplicity View Post
UPDATE:

We added a relay between the hard ground wire and crank ground terminal. It works just fine, no start in gear, start in neutral.

Yet, after the fact, I thought it may not have been necessary because if the tranny is in gear, the neutral switch should not pass 12v, so the circuit isn't complete. Yes??

Our next step is to add the rear ignition switch. This has never worked and will be welcomed when it comes to troubleshooting we won't have to constantly go to the front ignition.

By removing the interlock system, the rear panel diodes and adding the rear ignition switch, it should make the mechanical/electrical systems more mechanical and simple to assure more reliability.
Great job on the troubleshooting!

Isn’t there a rear ignition switch already?
Mine has one in the vim box.

I previously posted the vim box wiring, let me know if you need it I can post it again.
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Old 08-30-2021, 08:21 PM   #67
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Great job on the troubleshooting!

Isn’t there a rear ignition switch already?
Mine has one in the vim box.

I previously posted the vim box wiring, let me know if you need it I can post it again.
I downloaded a bunch of the files you uploaded on this and another thread.

The rear ignition was there, but not working. We're reinstalling it, but not using the diodes, at least that's the plan.
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Old 08-31-2021, 01:56 PM   #68
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Quote:
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I downloaded a bunch of the files you uploaded on this and another thread.

The rear ignition was there, but not working. We're reinstalling it, but not using the diodes, at least that's the plan.
I believe the diodes might be required. From What I can see in the diagram they are used to control the direction of current flow, to be able to use one starting circuit at a time.

BTW, another method of checking the quality of the wiring / connections is using an analog ohmmeter instead of a digital.
On an Analog meter, set it to Ohms, then you can either sort the wiring you are testing to ground and a clean wire will show infinity or zero ohms. If you get any type of resistance reading that could indicate either a dirty connection or a branch circuit, crossed wires or a high resistive open.

Another method would be to run a clean "New" wire, connect the two wires on the far end and on the near end, again check for resistance.

This method might be better than checking it to ground.

Toning is great and work as designed but this method actually test the quality of the line.

This method is old school and still in use today in the copper splicing world.

Keep us posted, I am following your work...great job so far!
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Old 08-31-2021, 02:05 PM   #69
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I add this for informational purposes, for those who really do not understand what a simple diode is and what functions it can serve.

All RE Amtran owners could benefit from this info...IMHO...

https://www.alliedcomponents.com/blo...-silicon-diode


A diode is an electrical switch commonly made of semiconductor material, such as silicon. It consists of two terminals: positive (anode) and negative (cathode). It is often used as a rectifier, which is a device that converts AC to DC with current flowing in one direction. Rectifiers can be found in electronic components such as radios, DC power supplies and high-voltage transmitters. Diodes take on many forms, such as vacuum tube diodes, semiconductor diodes and mercury-arc valves. A diode operates in conjunction with a resistor within a circuit.

Voltage Direction- The direction electrons flow in a diode is characterized by forward and reverse modes. In a forward-biased diode, current flows in a positive direction, whereas in a reverse-biased diode, current flows in a negative direction. Here's another way to understand it:

forward-biased diode = on (or "turned on")
reverse-based diode = off (or "cut off")

Ideal Diodes - A reverse-biased diode is said to be an open circuit. But when the diode is on, it acts as a short circuit. Ideally, the diode operates as an open nonlinear circuit with a fixed, constant voltage drop. This model is favored in the engineering field due to its simplicity. It is based on the concept that "forward conducting" has a minor fluctuating voltage drop from about 0.6-0.8 volts, with the assumption that the amount of voltage is constant at 0.7V.

The circuit can only be analyzed as linear if the voltage signal doesn't exceed one or more break points. Additionally, the ideal diode has zero resistance to current flow in one direction and high resistance in the opposite direction.

Conclusion- Diodes allow current to flow freely in one direction while limiting flow in the opposite direction. The purpose of a forward-biased diode is to allow current to flow in a forward direction, while restricting current to flow in the reverse direction. A reverse-biased diode reflects negative voltage. The most common diodes are semiconductor-based.
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Old 08-31-2021, 02:23 PM   #70
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Hey Ewo1...I'm with you on the diodes and their functions. In this case, I actually encouraged Simplicity to replace that diode junction (a T in plumbing terms) with a SPDT switch to toggle between front and rear start functions. My biggest concern was the way those two diodes were just dangling off their leads, subject to vibration and lead fracture. In the interest of durability, I suggested he either pot those diodes (a harder task) or install a "front/rear" start switch like many buses have.

Thanks for sharing and helping out!
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Old 08-31-2021, 02:31 PM   #71
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Quote:
Originally Posted by rossvtaylor View Post
Hey Ewo1...I'm with you on the diodes and their functions. In this case, I actually encouraged Simplicity to replace that diode junction (a T in plumbing terms) with a SPDT switch to toggle between front and rear start functions. My biggest concern was the way those two diodes were just dangling off their leads, subject to vibration and lead fracture. In the interest of durability, I suggested he either pot those diodes (a harder task) or install a "front/rear" start switch like many buses have.

Thanks for sharing and helping out!
I like the idea of a SPDT switch! Would be a great thing to carry in the emergency spare parts box while out on trips!

I wouldn't be too concerned about the rough handling of diodes though. Those silicon diodes can handle lots of vibration. Keep the leads short and I see no problem but a SPDT switch...That's a great idea !
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