Master switch no power

thomasinnv · April 26, 2019, 01:38:25 PM

How many of what voltage did you get at the ecm? With switch on or off? It's been a while since I have been into mine so my memory may be a little fuzzy, but I believe you should have 3 pins with voltage on them at the ecm with switch off, and one that comes alive with switch on.

Before resolving yourself to a bad ecm I would try to find someone that can plug into it in the vehicle and verify what it is or is not doing. There are a few things that are pretty simple that can keep it from starting even if all the appropriate voltages are present at the ecm. Srs and trs for starters. It's not completely beyond the realm of possibilities that something non related to your battery woe's has coincidentally happened at the same time.

Jcparmley · April 26, 2019, 01:48:44 PM

Your batter bay look much more organized then mine. The PO has this entire system messed up. For one I don't have a vanner like yours. Also, next to the two black boxes in your pic I have a third black box. I had to go and pick up my girls and I'm not at the bus anymore so I don't have good pics but I will take some tommorow and post them. For now here is the pic of the third black box I have.

Quote from: Jim Blackwood on April 26, 2019, 01:12:07 PM
Actually it probably is something but let's stay on task. JC my bus is also a '96 and may be close to yours on the production number. My VIN is 48598, you haven't said what yours is that I've seen. Anyway a few quick notes: First, on my bus it doesn't matter if the stairwell lights are on or off the bus still starts anyway. That could have been defeated or could have come that way.

I'm attaching photos of the battery bay. You should be able to blow them up large enough to compare the wiring to your own. If everything matches move on. If anything doesn't, first identify what it is and don't make changes until you are certain they are going in the right direction.

I have a photo of that big sucker above the Vanner if you need it, likewise one of the yellow remote box in the engine bay. I think only the two switches on the right can keep it from running though and they are pretty self explanatory.

Let me know what else you need.

Jim

daddysgirl · April 26, 2019, 01:58:28 PM

Quote from: Jcparmley on April 26, 2019, 01:22:49 PM
.
If the pos and negative were flipped wouldn't my voltmeter read -volts?

Pos and neg...batteries flipped, leads flipped,...will have different readings. I have an old school analogue meter, but I have seen circuit boards where the entire printed circuit evaporated while trying to pull the current to trip the protection breaker because someone hooked the batteries up backwards. That mistake will kill electronic equipment.
Just about every electrical item on the bus has a sticker or label to remind you about the 24 negative ground system. IMHO...It's one of the top three most important things to remember, that I am confident you will not soon forget. You'll be the electrical wizard when you're finished with this project.

Jcparmley · April 26, 2019, 02:06:34 PM

I'm no longer at the bus but when I tested the harness going into the ECM the main dash switch was on. I will need to go back and test the pins again. I need to find in the manual a pin layout.

I was thinking the same thing as far as having someone come out and test the ECM.

I think I need to make sure the battery bay is back to the original MCI set up and then proceed from there. The PO wired this battery bay differently than what's in the manual. Do you happen to have some pics of your battery bay like Jim sent?

Quote from: thomasinnv on April 26, 2019, 01:38:25 PM
How many of what voltage did you get at the ecm? With switch on or off? It's been a while since I have been into mine so my memory may be a little fuzzy, but I believe you should have 3 pins with voltage on them at the ecm with switch off, and one that comes alive with switch on.

Before resolving yourself to a bad ecm I would try to find someone that can plug into it in the vehicle and verify what it is or is not doing. There are a few things that are pretty simple that can keep it from starting even if all the appropriate voltages are present at the ecm. Srs and trs for starters. It's not completely beyond the realm of possibilities that something non related to your battery woe's has coincidentally happened at the same time.

daddysgirl · April 26, 2019, 02:16:54 PM

That box is a 50 amp manual reset circuit breaker. Do you know what it is protecting? Anyone have one like it?

Jcparmley · April 26, 2019, 02:33:27 PM

I have no idea what it it's protecting.

Quote from: daddysgirl on April 26, 2019, 02:16:54 PM
That box is a 50 amp manual reset circuit breaker. Do you know what it is protecting? Anyone have one like it?

buswarrior · April 26, 2019, 03:07:04 PM

We used those heavy manually resetting circuit breakers in Big Transit to protect the wheelchair lift.

Got one/had one?

Happy coaching!
Buswarrior

Jim Blackwood · April 26, 2019, 03:51:09 PM

I hope this is what you asked for. I'd be happy to post anything you'd like to see as long as I know what I'm trying to get a shot of.

First time I've had the cover off that panel. Guess that's a good thing.

Jim

daddysgirl · April 26, 2019, 03:58:47 PM

Nice looking junction box. They don't change much.

thomasinnv · April 26, 2019, 03:59:39 PM

JC do you have a wheelchair lift?

Jcparmley · April 26, 2019, 04:40:45 PM

Yes i do

Quote from: thomasinnv on April 26, 2019, 03:59:39 PM
JC do you have a wheelchair lift?

Jcparmley · April 26, 2019, 04:45:48 PM

Hi Jim

Can you get a pic of the back of the switches in that rear j box. I have a wire hanging that belongs on the back of one of those switches.

Thanks for all the help guys and gals.

Quote from: Jim Blackwood on April 26, 2019, 03:51:09 PM
I hope this is what you asked for. I'd be happy to post anything you'd like to see as long as I know what I'm trying to get a shot of.

First time I've had the cover off that panel. Guess that's a good thing.

Jim

thomasinnv · April 26, 2019, 06:52:24 PM

The 50 amp breaker in question is for the wheel chair lift

Jim Blackwood · April 27, 2019, 07:16:23 AM

Back of the switches? Hmm... It has a toggle switch on the left side with a red cover but I don't remember seeing other switches. I'll take another look. You aren't referring to the yellow remote panel by any chance are you?

Definitely with a lift you'd have more wiring. Was that the part that you removed? I thought there was something. I'm pretty sure you'll find some sort of interlocks with that wheelchair lift. If there is anything Corps are scared of it's a disabled person. Big faucet that's hard to turn off. Really good chance that's where you will find your answer, some lift related wiring that lost continuity in the removal process.

Jim

thomasinnv · April 27, 2019, 07:19:54 AM

Lift interlock does not disable starting of the engine, it just doesn't let you release the parking brake. Ask me how I learned that one? Lol

If he has power on stud 4 of the ddec junction block then he should have ignition power to the ecm. Thats the same circuit that also applies power to the diag ports.

JC you need to find a pinout for the ecm and check for ignition power. I would find it for you but I'm on my way out the door. I know I have it around here somewhere.