This Bus Nut is about to go Nuts!

Bryan · January 19, 2015, 06:08:50 PM

Hey guys, the bus nut I'm referring to in the title is me! I'm hoping that one of you Bus Nuts can save me

I've been dealing with an issue for over a year now. Basically when I hit a bump a certain way, I briefly loose all power to engine and electrical things like headlights, and dash lights. For the brief moment that the power is off, the "no charge" dash indicator light turns on and I also hear a clicking noise to the left panel of the driver seat which I think is a circuit breaker. But let me give you some more details.

I first noticed this problem not to long after I got it (and it wasn't a bump in the road), it would happen when I would rev it to high RPMs preparing to shift to the next gear. As long as I didn't rev to hard, it wouldn't happen... but that only ended up lasting about a week. For months after that, no amount of revving the engine would cause it to do it anymore.

I then started noticing these same characteristics when I hit a bump a certain way (mainly hard quick bumps like pot holes, or railroad tracks). I didn't notice it for a while. In the meantime I had an automatic transmission put in (boy is it nice!!!!) but I'm still experiencing the bump issue.

I have taken it to a good mechanic that has spent many hours looking for beat up wires, frayed wires, etc. He found some and fixed all of those. He even found one that he said was so barely touching that he didn't know how it was even working. This one went to an important solenoid. He thought that would have fixed it, but it didn't.

I've taken it back to him multiple times, and he says he has looked that bus over 100 times and chased wires, etc, and is stumped as to why it's still doing it. He thinks that it's potentially a solenoid somewhere that is cracked a little on the inside and is getting hot and a bump creates the momentary disconnection. But to me, that still doesn't explain the headlights turning off, or the circuit breaker clicking? Or does it?

What do you guys think this could be? Thanks for your help!

P.S. - the "no charge" dash light is also on when ignition is turned on, but engine is not started. (didn't know if that helped)

mung · January 19, 2015, 06:11:48 PM

First place to check is a loose ground. Start at the battery and work your way back.

Nick Badame Refrig/ACC · January 19, 2015, 06:43:24 PM

Hi Bryan,

I second the ground issue..

I personally chased a similar problem and found a corroded ground lug in my drivers
electrical box.

Good Luck
Nick-

Bryan · January 19, 2015, 06:53:06 PM

Thanks guys! If this is truly a ground issue, then why would I still have enough power to turn on the "no charge" indicator light. It seems that I would have ZERO power? I'm I correct in thinking this?

buswarrior · January 19, 2015, 07:04:48 PM

More than one major ground...

Good luck, I feel your pain!

happy coaching!
buswarrior

rgrauto · January 19, 2015, 07:21:18 PM

Bryan my bus had a bare wire and every time it shorted out it tripped a breaker. As soon as the breaker cooled down everything worked again,almost to the second. I would check all the grounds and then check the main wires that supplied powder to everything that is effected . Hook up a battery charger, turn everything on, no radio,you want quiet so can hear elect. popping and cracking and start wiggling wires and you may find the problem. HTH,Glen

Bryan · January 19, 2015, 09:59:14 PM

Thanks guys! I appreciate your input. When you say check the grounds, aren't there like many many grounds on the bus? It seems that the mechanic would have looked for this too right?

p.s.- I'm far from a mechanic

pvcces · January 19, 2015, 10:33:37 PM

Dealing with connections made of different metals is a special headache. All such a joint needs to corrode is a little conductive liquid, such as dirty water, which acts as an electrolyte. That turns the joint into a weak battery.

Aluminum is especially difficult to maintain good connections. Bus frames and skins make rotten grounds and should be avoided. Another case is the starting circuit; the ground side needs to be only by battery cable all the way from batteries to the starter. The alternator output relies on the starter ground.

A failed ground in a bus can damage driveline components, so good grounds are very important.

Good luck.

Tom Caffrey

robertglines1 · January 20, 2015, 05:35:57 AM

On a Mci 8 it happen to me. I got lucky and found it rite off. Was one of the relays with a bunch of pins on bottom that had a bad connection in socket. cleaned up reinstalled and no problems for the next several years I owned it. Also check for a pin/socket that has been pushed down to far in holder. Bob

luvrbus · January 20, 2015, 06:10:02 AM

Relays become weak over time they are just a coil I would be looking for a bad relay on the headlight system if the grounds are all good and that is a 12 volt system check and be sure no one has installed a 12v relay to fields on the alternator it requires a 6 volt relay

gumpy · January 20, 2015, 06:58:13 AM

Initially I figured the clicking you hear is probably the headlight relay shutting off, which of course is why the headlights go out.
But in looking at the 4107 schematic, it appears there is no headlight relay. The headlights are switched directly from the hot bus.

That means you are losing power in the 12v bus.

If it was just your generator, then you wouldn't lose power to the headlights because the batteries would continue to power the bus bar. So,
the problem is probably between the batteries and the main 12v bus in the driver's compartment. It's the hot wire, not the ground. Check
the connections of the cables on the battery junction stud.

According the schematic I have, there's a 00 wire from that stud that feeds a bus bar in the ventilation compartment. Need to check this
connection. Then, the main bus bar is fed from a 90 amp circuit breaker on the ventilation bus bar. Need to check this. It's possible that the
circuit breaker is corroded or loose, or the connections on the bus bar or the wire off it are corroded or loose.

Then, check the connection at the main bus bar. It appears there are potentially 5 wires connected at the main bus bar where the feed comes
in from the ventilation bus. This is a prime location for loose wire or corrosion.

The click you are hearing is either your engine run magnetic switch or your generator magnetic switch. Most likely, it's the engine run switch, since
it's coil is fed from the 12v bus bar, through the engine run switch whereas the generator magnetic switch coil is fed from the generator relay.

The only thing I can't figure out is the part about the "no charge" light because none of the schematics I have show a generator tell tale light so I can't
figure out how it's connected and why it would be on if the bus bar loses power.

Bryan · January 20, 2015, 07:56:21 AM

Quote from: gumpy on January 20, 2015, 06:58:13 AM
Initially I figured the clicking you hear is probably the headlight relay shutting off, which of course is why the headlights go out.
But in looking at the 4107 schematic, it appears there is no headlight relay. The headlights are switched directly from the hot bus.

That means you are losing power in the 12v bus.

If it was just your generator, then you wouldn't lose power to the headlights because the batteries would continue to power the bus bar. So,
the problem is probably between the batteries and the main 12v bus in the driver's compartment. It's the hot wire, not the ground. Check
the connections of the cables on the battery junction stud.

According the schematic I have, there's a 00 wire from that stud that feeds a bus bar in the ventilation compartment. Need to check this
connection. Then, the main bus bar is fed from a 90 amp circuit breaker on the ventilation bus bar. Need to check this. It's possible that the
circuit breaker is corroded or loose, or the connections on the bus bar or the wire off it are corroded or loose.

Then, check the connection at the main bus bar. It appears there are potentially 5 wires connected at the main bus bar where the feed comes
in from the ventilation bus. This is a prime location for loose wire or corrosion.

The click you are hearing is either your engine run magnetic switch or your generator magnetic switch. Most likely, it's the engine run switch, since
it's coil is fed from the 12v bus bar, through the engine run switch whereas the generator magnetic switch coil is fed from the generator relay.

The only thing I can't figure out is the part about the "no charge" light because none of the schematics I have show a generator tell tale light so I can't
figure out how it's connected and why it would be on if the bus bar loses power.

Gumpy, thanks for looking into this so deeply. You definitely know more than I do, but I'm determined to fix this. I just have a few questions. When you are referring to the ventilation bus compartment, you are referring to panel beside the driver seat correct? Also, I'm a little confused on what you mean when you say "generator", If you are referring to the actual generator we use for DC power on the bus to power fridge, etc, then that isn't even hooked up on this system, it's separate, but maybe you mean something else when you say "generator"? Thanks for the clarification.

And again, thanks so much for taking the time to look into this with the details!

gumpy · January 20, 2015, 09:31:42 AM

Quote from: Bryan on January 20, 2015, 07:56:21 AM
Gumpy, thanks for looking into this so deeply. You definitely know more than I do, but I'm determined to fix this. I just have a few questions. When you are referring to the ventilation bus compartment, you are referring to panel beside the driver seat correct? Also, I'm a little confused on what you mean when you say "generator", If you are referring to the actual generator we use for DC power on the bus to power fridge, etc, then that isn't even hooked up on this system, it's separate, but maybe you mean something else when you say "generator"? Thanks for the clarification.

And again, thanks so much for taking the time to look into this with the details!

No. There's evidently an electrical panel of some sort inside the compartment where the heater and air conditioner blowers are located, or maybe where the condensor fan is. I'm not familiar with that bus, but typically the A/C compartment is located in front of the first bay. Maybe someone with more experience with the GM buses will chime in.

In the manual (Sec 7, pg 123) it says: "Ventilation compartment apparatus panel is located in the ventilation compartment on the lower right-hand air duct plate assembly. Components of the ventilation compartment apparatus panel are identified in figure 9 on next page."

By generator, I mean the alternator. In the schematics, they refer to it as a generator. I believe that early on, they used a generator and the rectifying diodes were separate, but not sure about that. The nomenclature still refers to the alternator and related components as a generator. The terms come from the schematic.

By the way, do you have a maintenance manual? Id so, do your electrical schematics show a "no charge" tell tale? Is so, can you scan it or photograph it and send me a copy?

Cary and Don · January 20, 2015, 09:58:00 AM

The ventilation compartment is the first door to the left of your entrance door. The relays he is talking about are the two top round relays high up on the left wall behind the air tank. One of those wires go straight up to the bus bar beside the driver seat

Try turning on the run switch and headlights. Have somebody go in and try to wiggle that main wire on the the bus bar and see if anything blinks. I would take the main wire from the left relay to that bus bar in driver control panel loose at both ends and check for continuity end to end and to ground. If it shows ground it is damaged someplace.

As you have found out, that is a hard one to find. Try and wiggle as many of those wires going up there that you can and watch your lights for any response. It is a loose wire or a damaged wire someplace.

You really need the CD with your manuals and all the wiring diagrams.

Don and Cary

Bryan · January 20, 2015, 11:11:12 AM

Quote from: gumpy on January 20, 2015, 09:31:42 AM
No. There's evidently an electrical panel of some sort inside the compartment where the heater and air conditioner blowers are located, or maybe where the condensor fan is. I'm not familiar with that bus, but typically the A/C compartment is located in front of the first bay. Maybe someone with more experience with the GM buses will chime in.

In the manual (Sec 7, pg 123) it says: "Ventilation compartment apparatus panel is located in the ventilation compartment on the lower right-hand air duct plate assembly. Components of the ventilation compartment apparatus panel are identified in figure 9 on next page."

By generator, I mean the alternator. In the schematics, they refer to it as a generator. I believe that early on, they used a generator and the rectifying diodes were separate, but not sure about that. The nomenclature still refers to the alternator and related components as a generator. The terms come from the schematic.

By the way, do you have a maintenance manual? Id so, do your electrical schematics show a "no charge" tell tale? Is so, can you scan it or photograph it and send me a copy?

I do have the manual. I will be looking for that and will send you a picture if I can find it. Thanks!