Hey guys, today we took the bus out for a spin and had a new sound coming from the left dash area (pic below to show area) and it was like a rattling sound. If I was pressing the gas I would loose power the. The rattling would stop and I would have power again. It would only last a second or two. And it happened quite a few times weather I was pushing the gas or not. Also, anytime it rattled, the no charge light would come on (also see pic below) thanks for your help.
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this sounds like old bus stuff....open the wiring panel and see if something is lose. troubleshooting is a long time in learning.......could be your master switch failing...don't know your bus so you need to start following wires etc...
Relays can make a chattering sound when clicking on and off. Resettable breakers will chatter if there is a problem or short. The two things are probably related. Find the sound and you have found the circuit that has a problem.
Don and Cary
How was your air pressure? Sounds like a low air buzzer to me.
Could also be related to his other thread about trailer lights! If there is a wiring problem relays & breakers will kick in and out!
;D BK ;D
Wasn't there also a thread about a knocking sound in the engine compartment a couple weeks ago?
Just being an armchair mechanic here, but Zub's post works for me. I did once have a failing main switch and engine power would go off and on. I do not remember if there was any relay noise, but it makes sense that the relay would chatter as it lost and regained power. So I would guess at the bad switch, a bad relay of a bad connection to either.
hey guys! Thanks so much! Yes, you are correct I was the one with the odd engine knocking last week, and also the tail light voltage problem. The engine hasn't knocked since that day. But all of this could be related together. I haven't taken that side panel off yet where the dash chattering is to look behind it for issues. I suppose that will be my next step. I don't know to much what I'm looking for but I will for sure make sure all wires are in tact and go from there.
There is a solenoid in that panel that clicks on/off when there is not enough load on the alt. Upper left as I recall.
The original alt is so big and a conversion load so small compared to a passenger bus the alt keeps turning on/off.
The solenoid keeps the AC/heat blower from operating when there is not enough output from the alt. When the original blower for AC/heat is on it won't click. Try it.
I put a switch on mine, it drove me nuts. Now when I need heat I turn this switch on first, it is just a grounding switch for the solenoid.
Quote from: gus on February 18, 2014, 04:18:52 PM
There is a solenoid in that panel that clicks on/off when there is not enough load on the alt. Upper left as I recall.
The original alt is so big and a conversion load so small compared to a passenger bus the alt keeps turning on/off.
The solenoid keeps the AC/heat blower from operating when there is not enough output from the alt. When the original blower for AC/heat is on it won't click. Try it.
I put a switch on mine, it drove me nuts. Now when I need heat I turn this switch on first, it is just a grounding switch for the solenoid.
Are you referring to the switch labeled "Fan"? Just turn that on and see if it stops it.?
Speaking of heat, I'm not even certain the bus heat works, the PO said they used floor heaters in the winter. The ceiling A/C units put out great AC but not to much heat.
There is a driver's fan switch.
The big blower is labeled Heat on the original, with your panel and mine it could be anything since neither is original! You can hear it run it is so big but originally it will only run with the alt on adequate output.
With so many conversion changes it could be wired any way but!!
This is what mine looks like now. After looking at the manual, it appears that the generator ignition is over the original heater switch. Any suggestions?
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I had forgotten, there is a solenoid in the "engine run" circuit in the side elec comp. Open that panel and maybe you will be able to see/feel the noise maker.
Ok so today the bus is no longer starting. It also made that same chatter while trying to start. We are pretty sure it is what I have pictures below which we think is the starter solenoid? Where can we find another one? Checked auto parts stores and they didn't have it.
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In general terms, a "starter solenoid" normally refers to the high current relay/switch that actually engages the starter, and would have hefty battery-like cables attached to it. It's nearly always in the engine compartment somewhere between the batteries and the starter. Often it's integrated with the starter assembly itself.
What you have there is more likely a relay. Given that your previous symptoms happened when the bus was already running, it's more likely something to do with the run circuit, not the start circuit. Can you trace where the wires from this relay went? This is where you could really use the relevant manual pages for your bus, especially the circuit diagrams.
If you really need to move the bus, odds are the bus could still be started/stopped from the rear, assuming the original panels are still there.
Match the posts on the old relay a cube relay will work in place of the old coil, point type relays just find a good parts guy that will match the open and close terminals
good luck
What Luvrbus said!. Take the old relay to a good parts store and try to match it up. It does not have to look exactly the same. You just care about the terminals functioning the same. Getting parts for your bus will often be like that. Parts clerks will ask about the vehicle, but that rarely is of any use. You have to match a part. They want to look it up in a catalogue by make and model, but these buses are not in their catalogues. Aside from which, things might have been altered over the years.
We ended up finding another relay like this, swapped it and still have the same problem. We can get the bus to start but it will quit after a few seconds.
Something else we noticed... The "no charge" light on the dash is on, so just to rule it out, we swapped item 8 and item 9 (see below) and it kept the "no charge" light from coming on but our overall problem is still the same.
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I'm sending you a photo of the driver's panel by email. That relay has nothing to do with starting as you can see.
When you start the engine and it quits soon do you have any air pressure? It sounds like the classic case of having the rear run switch turned off. If you haven't moved it it may be so badly corroded that it has failed open. Happened to me. I had to jump wire around it.
That relay doesn't have the same terminal layout as a cube relay so they won't work unless you rewire the whole thing. You will need the cube relay base and will need to make sure it will carry the required amps. The average cubes are 30-40 amps which should be enough for a starting circuit.
I think of solenoids as the ones like on starters and relays as the smaller ones like cube relays, but that isn't technically the correct definitions. They are all remote switches which covers all!
A cube relay will not replace the bus steel, round solenoids with large terminals because none of the large wires will connect. I suppose you could rewire the whole thing by using a cube relay socket but the wires are nowhere nearly as large on most.
That photo looks like the horn relay or stop light relay. As you can see in the photo there are only four of those in this panel. My 4107 start relay is in the back left panel above the engine and is a steel, round solenoid with large terminals
Oh my goodness!!! The engine run switch! I guess that was my first time with the classic case of that lol. This still hasn't solved my possible problem of the clicking noise that started this post. I had thought all this was related but maybe not being that it was just the engine switch.
Again the clicking noise will come from the left driver panel and I will loose power at the same time it makes noise.
Man thank you so much for helping. I still can't get over the engine switch haha.
The charging system will have a charging relay your bus is probably 24volt the charging relay will be 12 volt for a 24 volt 50D alternator if 12 volt it will be 6 volt you can buy the adapter to go from coil type relays to the cubes if you choose, check the field on the alternator when it shuts off and see if it is still magnetized
Suspicious of the low oil or high temp buzzer begin activated by a sensor which is also shutting down your engine.
Do GMs have a safety shutdown system like the MCIs do? I don't know.
I understand the engine doesn't stop so feel the relays in the panel when clicking starts, it will be easy to identify it and you won't get any kind of shock.
Do you mean the toggle switch on the panel? I call that the engine run switch? I've had at least three of those old toggle switches fail on my two buses. Usually the spring inside fails or it corrodes and opens.
Interesting that the photo of that panel you posted is not the same as the one in my 4107 manual?? Yours is an actual photo of the panel and mine is a drawing without the wires?
8 and 9 are the only ones that I think you could hear, the others are probably too small to be heard. Or maybe 7 is sounding off for some reason?
The noise maker in mine was/is the Generator Magnetic Switch (9) which actually has nothing to do with the gen, it cuts off the blower motor if the gen isn't producing adequate power! (8) would make the same sound.
These old elect systems get so changed around in conversions, especially the alarm systems, that they cause many very strange things to happen. Often the quickest way is just to wire around them.
I'm still suspicious of the rear elect panel, switches there catch a lot of crud from the engine and fail/rust.
Thanks Gus! Just to clarify, the engine does not turn off but it DOES loose power when the chatter happens. As soon as chatter stops I feel like I have gas again.
When you say wire around 8 and 9, you mean these magnetic switches really aren't even necessary to have?
Thanks again! 😃
You really don't want to wire around the charging relay when you start to lose power check the voltage on the alternator I bet it is very high loading the engine IMO, Bill's 4905 would do the same his is a 24 volt system and would produce 32+ volts slowing the engine down and had no power
His was a grounding problem the regulator will not regulate the voltage when it does not see a ground only took a week to find that out lol
Yeah, what Cliff said. That's a much better theory than what I had, and from a much more reputable mechanic :)
No, I said that very poorly.
What I wired around was the rear panel engine switches because they were so corroded they were causing problems. Sorry!
This didn't cut anything out of the circuits except those rear switches. I was afraid to try to install new ones and mess things up even more!!
I'm having another problem now, the VR is not getting the full 12V which also comes via the rear panel so I probably have another jumper wiring to do. That rear panel on mine has no cover so the whole thing is a mess.
Grounding of the VR is, indeed, a problem. The PO had added an additional ground wire to my VR at some time.
Yea my rear panel is the same way, it doesn't have a cover on it. Lots of dirty wires. I'm rerunning my tail lights, signals, brake lights, etc, and also installing reverse lights to an unused switch. By the way, where can I get those dash switches? Some of mine need replacing.
P.S. - what is VR?
If you mean generic toggle switches they are found anywhere, WM, auto parts, hardware & etc. There are some cheapos out there though, maybe some not worth installing.
Make sure you don't try to run too many amps through those long wires and small switches, better to use cube relays found anywhere also.
VR= voltage regulator. I tend to abbreviate a lot since typing is not my favorite sport!
I looked up the part number for the switches that replace what's already in the bus like the factory ones, and they were $50-$75 each. EXPENSIVE SWITCHES! I was able to use one of the switches from another spot that wasn't being used anymore, and I swapped them out. I installed some halogen lights to the back of the bus for reverse lights, I ran those to one of those switches. You are saying I should use a cube relay for those correct? I noticed that there was a whole volt lost on the wire when I turned the switch on. Do you think that is due to it running thru the small switch?
Also, I had to jump the bus off tonight because I left the battery on to long while working with the lights. How many volts does it take to start the bus? I had 11.6 volts when I measured it with a voltage reader right on the battery. Thanks! :)
Volts mean nothing AMPS are needed (900) for a 12 volt starter at least
Bryon,
For a liquid lead acid battery, 11.6 volts at rest means it's fully discharged.
That battery, when fully charged and at rest will run about 12.7 volts.
These numbers are for 77 degrees F. Voltage will vary a lot with big temperature changes. I agree with Cliff; allow for lots of current (amps) while cranking the engine if you want to avoid burning something up. Rebuilders consider weak batteries a major cause of starter failure.
Get those batteries a good charge!
Tom Caffrey
in answer to your question re voltage drop on the 30'+ of wire....that is why you use cube relays....the switch at dash is low voltage.oops.I mean ampage!. ie only controls the relay....then at the back of the bus were the batteries are you tap off a nice thick lead of "+" charge and use that as the load supply to you reverse lights in this case. Unless u want torun big fat wires to the back....or want to have lectric fires do a little research online vis a vis automotive wiring and u will learn what u need to know. alot of the bus people here know this stuff so well that they wont answer the really simple stuff. but the info is out there.
Well, as luvrbus said, it is the amps that are the problem on those long runs through small switches.
High amps, long runs, high resistance = heat = smoke/fire.