This Bus Nut is about to go Nuts!

[Bryan]

Ok and what exactly exactly is the bus bar? Sorry

[gumpy]

Ok and what exactly exactly is the bus bar? Sorry

The bus bar would be the metal common bar that all the circuit breakers are connected to. There are photos in the manual. Section 7.

Don has a good point regarding the continuity testing, and possible grounding. I don't think the main wire is grounding out, though, because you
said the disruption is very brief. If it were a short on the wire, the circuit breaker would probably trip and it takes awhile for them to cool down
enough to reset.

[mung]

That is where I keep all my booze  

But really, it should be a long metal bar with a bunch of positive wires connected to it.  On my 4104 there are several bus bars in several locations.

[Bryan]

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?
[/quote

This is the image of the dash in my manual but this doesn't look like my dash in real life


]

[Bryan]

And here is my real dash. Excuse the green tape. The no charge light is actually hidden by the center of the steering wheel. You can almost see it. This was the only picture I could find until I get back to it shortly

[Lin]

I had a problem with the system shutting down momentarily that turned out to be a bad main switch.  When you turn the main switch on and off do you hear the same clicking sound in the side panel?

[gumpy]

I had a problem with the system shutting down momentarily that turned out to be a bad main switch.  When you turn the main switch on and off do you hear the same clicking sound in the side panel?

While a good point, according to the GM 4107 manual I have, the headlights are attached directly to the 12v bus bar. There's no relay controlling them, so it seems even with the main switch
on, the headlights could still be activated.

Bryan, maybe you can clarify that. Can you turn on the headlights if the run switch is off?

But, it could be a problem with the battery disconnect switch, I think, depending on which side of the battery junction post it's on.

The photos of the dash in your manual look like what I have. See if your schematics show a "no charge" tell tale or generator tell tale or something like that. I can't find any reference to one in the manual.
I suspect that maybe your bus is newer than my manual, or that is an add-on.

[Bryan]

Gumpy, it appears that we are looking at the exact same manual. I'm trying to learn something here. Is the ventilation compartment apparatus panel fed directly from the battery stud? Or is it connected somewhere into the battery compartment apparatus box?

Lastly, yes I can turn headlights on if run switch is off.

[gumpy]

Gumpy, it appears that we are looking at the exact same manual. I'm trying to learn something here. Is the ventilation compartment apparatus panel fed directly from the battery stud? Or is it connected somewhere into the battery compartment apparatus box?

Lastly, yes I can turn headlights on if run switch is off.

The feed should come directly from the battery compartment stud to the ventilation bus. If you look at the photo on pg 124 you'll see it coming in on the left side, second cable from the top. The top cable
on the left side is the one that goes to the drivers electrical box to power the 12v bus.

[Bryan]

okay, I have a pretty major update! I turned the headlights on tonight and went and beat on the ventilation compartment apparatus where the battery wire is coming into it, and sure enough it make the head lights flicker, so I took it apart, sprayed some corrosion cleaner on it, did some minor wire brush cleaning, and put it back together... but it still flickers? I'm going to post a picture, the red arrow is where the battery power is coming in. The blue arrow is supposedly the circuit breaker that goes to the driver panel. But pretty much anywhere I beat on that bar, it makes the headlights flicker. What do you think?

[rgrauto]

Bryan the best tools I have for testing wiring is my test light and a three foot wire with alligator clips on each end, The wire lets you jump circuits while the test light is attached so it gives you a visual when the power drops out. Hook the light up, beat on the panel and if the light go off then take the jumper wire jump circuits till you find the culprit. HTH. Glen

[gumpy]

okay, I have a pretty major update! I turned the headlights on tonight and went and beat on the ventilation compartment apparatus where the battery wire is coming into it, and sure enough it make the head lights flicker, so I took it apart, sprayed some corrosion cleaner on it, did some minor wire brush cleaning, and put it back together... but it still flickers? I'm going to post a picture, the red arrow is where the battery power is coming in. The blue arrow is supposedly the circuit breaker that goes to the driver panel. But pretty much anywhere I beat on that bar, it makes the headlights flicker. What do you think?

Following my previous line of thinking that the problem is loss of 12v to the front bus bar, I would, for testing purposes, take the wire off the blue arrow circuit breaker, and attach
it to the red arrow connection. I'm suspicious of that 90 amp circuit breaker.

I guess while you have them apart again, I would run continuity tests on both wires end to end, and while the test light is attached (see Glen's post above), wiggle the hell out of
the ends of the cables to make sure it's not a break inside the cable. Unlikely, but not unheard of.

And here's something else I just saw in the manual. Apparently there are multiple battery junction terminals. See pg 125. Two
of them seem to be pertinent to this discussion:
1. Battery compartment junction located on wall of rear baggage compartment above battery compartment, is accessible after removing guard mounted on top of battery compartment.
3. Ventilation compartment apparatus box battery junction, located on lower right-hand air duct plate assembly, is accessible through the evaporator compartment door.

I'm not sure about #3. Maybe that is the red arrow in your photo. Maybe there's another one in there. So, look where the text says and see if there's something else there. It seems that you are close to the problem if banging on the ventilation compartment causes the problem.

[Bryan]

Another update! I ran a jump wire around that 90amp circuit breaker, (pretty much what you were saying about attaching blue arrow to red arrow)... beat on it pretty hard, and NO ISSUES!!! So I guess it has to be a problem with that circuit breaker. Where can I find a replacement?

THANK YOU!

[digesterman]

Bryan am I hearing a big sigh of relief ? Hope you traced it down


Sent from my iPad using Tapatalk

[gumpy]

Another update! I ran a jump wire around that 90amp circuit breaker, (pretty much what you were saying about attaching blue arrow to red arrow)... beat on it pretty hard, and NO ISSUES!!! So I guess it has to be a problem with that circuit breaker. Where can I find a replacement?

THANK YOU!

Very possible. And with all the corrosion I see in your panel, I would consider replacing a few other items in there. Before you go replacing hard to find parts, I would
recommend  you bypass it completely as I indicated above, rather than using a jumper (you didn't say what size wire you jumpered it with), and take it for a long
drive to replicate the scenarios that were causing the problem to occur. Then, if you are sure it's not happening any more, replace the part.

I'm not seeing much in the way of 90 amp breakers (though I didn't search extensively), but according to the schematic that cable is a #1 so should be good up to about 130 amps.
You could go with an 80 amp breaker, or could probably go up to a 100 amp breaker with no issues. The 80 should be plenty for your needs. It looks like the headlights are probably
the biggest draw on that circuit. I assume all the interior lighting was replaced. Windshield wipers are on there, too. Not much else for current draw, so 80 amps should be sufficient.

I don't see a direct replacement, but here's one that I think will work, though you may have to move the bus bar assembly to fit it. Or, yo might have to make a new bus bar.

http://www.waytekwire.com/item/46913/HI-AMP-AUTO-RESET-80-AMP/

They have a similar 100 amp breaker, too, if you decide to go that route.

Waytek will also have a 20 amp panel mount breaker to replace that corroded one below.

BTW, you might be able to find one at NAPA or you might try a semi-truck parts house. Another option might be to call one of the local charter companies and
ask them if they might have one they'd sell to you.