Master switch no power

[Jcparmley]

Hi Jim

I have not done any dismantling of this bus.  The interior was all stripped by the PO.  There are some wires hanging from where the over head bins were.  I am nervous that those might short, or have already done so.  Therefore, I am going to tape those ends and make sure they are not exposed. 

Yes, I drove the bus multiple times.  The PO told me that he always unhooked the large cable between the two batteries when it was parked.  Before I purchased it I took the bus to a International Large Truck service center just to get a basic inspection of things like the brakes, bearings, structural issues, oil leaks, etc.  Just the basic stuff.  Everything checked out fine.  When I went to pick the bus up it wouldn't start and the batteries, even though they the master switch was turned off the batteries were less than 20 volts. 

So I took the two batteries out of my C3 bus and installed them in the new bus and it started and I drove home.  When I got home I parked the bus and charged the depleted batteries over night and put them back in the bus.  The next day went to start the bus and once again the batteries were run down.  So I disconnected them and charged them again.

Then I wired a battery disconnect onto the main ground above the left battery hoping that when turned off it would turn off whatever phantom load was draining the battery.  When I went to start the bus I got nothing from the main dash switch.  That's when I opened the dash to see if a wire was loose or disconnected from the main switch. 

That's when I wrote the post to get advice from you all.  I have followed the steps laid out in this thread.  I traced the power to the various circuits.  I also took the battery disconnect from the main ground and put it on the positive going to the main disconnect in the battery bay.  So other than wiring the battery disconnect I have not wired anything else.

It's nothing specific JC, but then maybe that is the problem. Electrical systems need a very organized and logical approach. You seem to bounce around quite a lot and I get the mental picture of a bunch of loose wires hanging willy-nilly in no particular order. My apologies if that isn't the case, I realize much of it comes from the DPO's add-ons and is unavoidable at the present. Actually I think you have made great progress and are probably quite near a resolution.

If I understand correctly, you did drive the thing before all this began right? So what exactly happened between then and your discovery that it wouldn't start? If you can nail that down then I think you can isolate the issue. Took the overhead bins and A/C units out right? But what else? Just doing that shouldn't ordinarily keep it from starting. Shorting out the overhead wiring might if it popped the right breaker somehow but that would be going pretty far upstream, probably past lesser breakers that should pop first. I suppose it could happen. You may find those indicator lights on one of the annunciator panels, I don't remember them but I'm still memorizing that stuff. I'll try to take a look tomorrow. Your manual should have everything that's there listed if you can look at those pages. Should be towards the front.

Jim

[thomasinnv]

SEL = stop engine lite
CEL = check engine light

They are located in the left side indicator panel of the dash. Bottom row 2nd and 3rd lights from the left. To verify thier position,  you should have a bulb test button located in the control panel by your left arm rest.

[Jcparmley]

Got it.  Yes, I will check that tommorow.  Acronym's always mess me up.  Good thing I don't work for the government.

SEL = stop engine lite
CEL = check engine light

They are located in the left side indicator panel of the dash. Bottom row 2nd and 3rd lights from the left. To verify thier position,  you should have a bulb test button located in the control panel by your left arm rest.

[windtrader]

After many years of being cheap on multimeters, I paid up some to get a nice, accurate clamping meter. It makes tracking down faults and following electrical connections really easy. Any flowing/non-flowing current is detected simply by clamping the wire. Something I should have bought many years ago but at least now in the toolbox. Actually tomorrow, going to track down where my left turn circuit is failing.

[luvrbus]

I say you have a short the ECM and WTEC will not kill batteries over night turn off the disconnect and make sure the alternator is not still energized 

[Jim Blackwood]

OK. Easy to get 'em mixed up now that there are several of us with these. I remember your first posts now.

So, it started and ran until it wouldn't start because the battery ran down. DPO removed the jumper between the batteries to keep that from happening. Sounds like you were unable to duplicate that because when you got to that point the engine wouldn't start. What did I miss?

If that's all there is, having the batteries at full charge should allow it to start. Since it doesn't, it stands to reason something else changed. Are the remote switches in the engine compartment set correctly? I'm not sure they can let it crank and not start, but it may be a possibility.

In fact, it seems to me that most if not all interlock circuits should keep it from cranking rather than prevent it from firing off but I can't confirm that. If so, I would definitely be looking at the fuel supply.

Jim

[buswarrior]

MUST confirm power at the ECM... all bets are off that wires are where they belong now, both dash and battery compartment.

We're going to have multiple disablement on our hands, chasing around like this...

PO removed centre cable from batteries??? That's strange, what's wrong with the stock battery switch? What he really was doing is disconnecting the 12 volt centre tap, and stopping a 12 volt parasite, at the same time as confirming no 24 could flow...

The small wires in the battery compartment have a high probability to be connected wrong....

Some of them might be grounds, some of them might be 12 volt, some of them might be 24 volt...

Prove each wire, approach the bus with no assumptions, identify the purpose of each, put where they belong...

The reason I am a huge advocate for establishing collection points for all these wires that never get disturbed by removing battery cables... stuff gets put back wrong...

I can tell you a Freightliner with a Cummins ISM in it, won't run or display the dash correctly if you reverse the positive and negative ECM leads to the battery... starter will crank, no fire... self inflicted wound... sometimes we are too smart for our own good?

If you mess with the fuel system, start a new thread...

Happy coaching!
Buswarrior

[Jcparmley]

So neither the SEL or CEL lights turn on when I flip the master dash switch.  I checked the continuity of all the ecm fuses and they all checked out as good.  I think somehow the ecm isn't getting power. 

SEL = stop engine lite
CEL = check engine light

They are located in the left side indicator panel of the dash. Bottom row 2nd and 3rd lights from the left. To verify thier position,  you should have a bulb test button located in the control panel by your left arm rest.

[luvrbus]

No lights no run there is a black box with all the ground connections check there and check the box under it for power all the power supply and grounds are there in the battery box 

[Jcparmley]

I have been following wiring schematic and confirming power at each junction just as everyone has recommended.  You are probably right in that the battery bay isn't set up correctly, the PO added battery cut off switch, etc.  I'm just trying to get it back to OEM.  I have determined the fuses for the ECM are good in the battery bay.  What is the procedure for checking the ECM for power?  Reversing the leads to the ECM is interesting.  I will check those out as well.  I am looking for a better guide for the OEM battery bay set up.  There are many wires in the bay that arn't in the illustration in the manual. 

MUST confirm power at the ECM... all bets are off that wires are where they belong now, both dash and battery compartment.

We're going to have multiple disablement on our hands, chasing around like this...

PO removed centre cable from batteries??? That's strange, what's wrong with the stock battery switch? What he really was doing is disconnecting the 12 volt centre tap, and stopping a 12 volt parasite, at the same time as confirming no 24 could flow...

The small wires in the battery compartment have a high probability to be connected wrong....

Some of them might be grounds, some of them might be 12 volt, some of them might be 24 volt...

Prove each wire, approach the bus with no assumptions, identify the purpose of each, put where they belong...

The reason I am a huge advocate for establishing collection points for all these wires that never get disturbed by removing battery cables... stuff gets put back wrong...

I can tell you a Freightliner with a Cummins ISM in it, won't run or display the dash correctly if you reverse the positive and negative ECM leads to the battery... starter will crank, no fire... self inflicted wound... sometimes we are too smart for our own good?

If you mess with the fuel system, start a new thread...

Happy coaching!
Buswarrior

[thomasinnv]

Don't just check the fuses for continuity, check for power. Good fuses don't mean squat if they have no power. Verify you have power there and let us know. Baby steps, we'll get you there. In the meantime I'll dig out my manual and look at the ecm schematic to see what the ignition circuit looks like from the switch to the ecm.

[Jcparmley]

Ok, I will check for power both at the fuse socket and through the fuse.  I am trying to find the ecm schematic now.  I really appreciate the help.

Don't just check the fuses for continuity, check for power. Good fuses don't mean squat if they have no power. Verify you have power there and let us know. Baby steps, we'll get you there. In the meantime I'll dig out my manual and look at the ecm schematic to see what the ignition circuit looks like from the switch to the ecm.

[luvrbus]

You check the power to the ECM in the rear panel I think it is terminal J and like stated check for power at fuse in the battery box when you remove the cover it has the terminal number if J is not right   

[Jcparmley]

I will check that terminal this afternoon.  If I have power at that terminal where do I go from there?  Where is the actual ECM box?

You check the power to the ECM in the rear panel I think it is terminal J and like stated check for power at fuse in the battery box when you remove the cover it has the terminal number if J is not right

[6805eagleguy]

From back of bus ECM is on right side of engine, just forward and down from compressor