2002 Bluebird All Amer. technical wiring question

[Sir Octobus]

Hi,

I have run into an interesting problem that I can't solve--the backup lights don't come on when I switch to reverse.

Here's what I know:

The bulbs and wiring from the lights up to the Doran light monitor are good.

I can jump an active wire at the monitor to activate the lights, they just don't activate when I put it in reverse.

I found a wiring diagram and traced a light blue wire (1322) from the Doran monitor back into the relay panel on the side, which appears to go into the dash area.

It seems like this blue wire is supposed to provide the power when reverse is engaged, but it doesn't.

I have checked all the fuses and there aren't any faulty.

I have checked the relays as best I can and found nothing.

All the other lights on the bus work.

Please help.

[johnbloem1974]

In my bus, the reverse lights are activated by a switch in the transmission. Only will come on when the bus is running. I can see if I can get a picture if that helps...

John

[Sir Octobus]

I was just in the process of doing some Internet searching and found someone referencing this switch. I know my transmission is a MD 3060, so if that’s what you have and you can get a picture of it, I would greatly appreciate it.

I’m hoping to find a video tutorial.

[johnbloem1974]

Yea, so I have an MT-643. Unfortunately pic won't help as we have different transmissions. I believe the 3060 may have that function through the TCM....but you're on the right track! Hopefully someone with more knowledge of the 3060 can chime in...

@cadillackid- your thoughts?

John

[Iceni John]

I also have a "neutral safety" switch on the side of my HT740 transmission that A) prevents the engine from being started if in gear, and B) only allows the Fast Idle to work when in neutral (and parking brake set), and C) actuates the reversing lights, all through the magic of relays. My transmission's switch is on, I think, its left side (the right side of a RE bus), and it's where the Morse shifter cable enters the transmission. Mind you, you probably have a new-fangled electronic transmission, so just ignore my old-fangled advice!

John

[Sir Octobus]

Is that neutral switch something I can reset or do I have to replace it? I guess I’m just not sure how it’s supposed to work.

[Sir Octobus]

Can low trans fluid have anything to do with this?

[cadillackid]

Originally Posted by Sir Octobus

Can low trans fluid have anything to do with this?

I believe on the 3000 series the reverse lights are activated by the TCM. there is a switch internal to the transmission.. since this is a fully electronic trans, the engine will need to be running and the transmission will need to fully engage the gear for the reverse signal to be sent.. so yes low fluid can affect it..



for reference the MT643 or the AT545 uses a pressure switch in the side of the trans.. . the switch activates when reverse gear engages and pressurizes the switch.. reverse lights wont work if the engine isnt running or trans fluid is very low.



the allison 1000/2000 use a physical switch based on the position of the shifter lever.. on those the switch can be internal or can be an external switch on the side of the trans at the shift lever.


ive only seen a couple HT7xx series transmissions and they are as John describes, an external switch on the side of the trans.

[Sir Octobus]

Thanks for the ideas. I have been testing with the engine on with the park brake engaged and stepping on the brake pedal but have not got anything.

I don't know if my fluid is low, but I'm going to check. I also plan on inspecting the Doran monitor to see if that has caused some kind of fault.

At this point I'm still trying just about everything.

[Sir Octobus]

So I checked the fluid level and it seems fine. The light blue wire that goes into the Doran monitor never gets power. I have used a voltmeter and measured it in neutral and reverse but it’s the same. I have checked all the white ground wires I can find and they are attached.

From what I can determine, the problem is that wire is not getting power when the reverse is selected.

I found a wiring diagram that shows the wires leading to a relay, numbered p123. I checked the panel on the bus and confirmed that relay is there, but I have no idea where to find it.