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Author Topic: Return trip from Arcadia & our 24vdc generator.  (Read 3041 times)
JerryH
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« on: January 02, 2007, 05:56:25 PM »

Had an uneventful trip down to FL.  The Kohler genset worked without any issue as needed.  However, when we departed Lady Lake, FL on 1/1/07 ... about 15:min. into the trip I turned on the road A/C.  Shortly thereafter the A/C stopped and the "Not Generating" tell tale was lit.   Hmmm, I thought.  I thought possibly air, but instead found four of four belts powering the generator were trashed. 

Well there we were on Rt-301, heading north on New Years day.  We passed autoparts store after autoparts store -- "Closed".  Found a Wal-Mart and "thought" they might have belts.  Nope!  Never looked before, but was hoping.  Was directed to a place up the street.

Ok, so I had "Da Book" (parts and maint.), but unless I missed something, there's no mention of the necessary belts or part number.  Next problem, find an autoparts store with 4 identical belts on hand.  We couldn't.  Unsure of the exact size, we did find something "close", but they only had 2.  Walked to another nearby autoparts store and they had 2 more.  Ahh problem.  Same number, difference makers and after hitting the air valve to tension the belts, 2 weren't the same tightness as the other 2.  That's not gonna work.  So we leave the 2 tight belts on the #2 and #4 pulley positions and head north -- all is good.  I try the A/C again.  Bad Idea.  No problem running 2 belts with NO A/C.  But once the load of the A/C is introduced, it toasted the 2 belts we had.  I struck out on finding any matching belts, which was fine as we really didn't have (or know) the "ideal" size for the application.

Ran 2 belts all the way home to PA without using the A/C.  Once the sunset in the FL/GA area, it was fine.  Didn't need it the next day (1/2/07).  Thanks to those who I phoned, picking your brains.

So does anyone know the factory specified belts for the 24vdc generator off an DD8V71??  Four belts in all.  You know, I had spare belts for the Kohler genset and the main fan (squirrel cage) ... but nothing else.  TAKE additional belts!

Jerry H.
« Last Edit: January 03, 2007, 04:37:26 AM by JerryH » Logged
Nick Badame Refrig/ACC
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« Reply #1 on: January 02, 2007, 07:23:01 PM »

Jerry,

We are glad you, Linda and the kids made it home OK!

Funny how, only the things that you never think will break..BREAK...

Nick-
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buswarrior
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« Reply #2 on: January 03, 2007, 01:32:37 PM »

Hello.

Good strategy to reduce the electrical load.

Also a great situation in which the redundancy of a good inverter/charger powered by the genset could double as your alternator.

For the occasional mileage busnut, which most of us are, I might suggest a good preventive maintenance practice would be to change out the belts every couple of years, putting the new ones on the coach, and putting the old ones underneath as spares.
Might be good to wrap some masking tape around them and scribe a date of some sort..... memory not what it once was, too much other more important stuff in there, I guess!!!!

This is common practice in both road and marine environments. The airplane folks do the same, but, for some reason, have little need for the spares......

Fast Fred has preached the virtues of this practice longer than I.

MCI sells the belts in matched sets. Call their 800 number and get a set sent to you.

Canada 1-800-665-0155

US 1-800-323-1238

Technical Support 1-800-241-2947

Online parts store at http://www.mcicoach.com/Parts-Service-Support/partsServiceSupport.htm

happy coaching!
buswarrior

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JerryH
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« Reply #3 on: January 03, 2007, 01:44:35 PM »

Hey, for what it's worth ... I phoned MCI who were quite helpful and got me the part number #8R-27-3, $10.45 ea.  Gotta get $100+ for free shipping or pay $30.00, $55.00 if over nited.

The MCI part number did cross reference at NAPA, in at $13.43 ea. and within 3-miles of my home.

But for sure ... check those belts.  While nosing around in doing the belt change, I also found some bundled wires (4 in all) which no longer had the appropriate wrap around the four of them.  So that'll be addressed when I swap the four belts tomorrow -- once the new belts arrive.

A side note, our main road air/heat blower is isolated (power-wise) to the 24vdc and I have no way to run it off our genset.  We could have run the house AC's off the genset if it got "really" bad ... but it didn't get to that point.

Jerry H.
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« Reply #4 on: January 03, 2007, 01:57:45 PM »

Jerry, for what it's worth I have learned from past experience that if you buy a match set of belts, they all have to be put on in the same direction.   You can tell the direction by keeping the numbers facing the same way, the embossed numbers not the painted numbers.A belt stretches different if put on the wrong direction, if two are put on one way and one the wrong way, you will notice the difference between the three, two will have more tension than the other one.

I have been a mechanic on the railroad and for other companies and have worked on many machines and if you don't put the belts on right you will notice the slack in the one that's wrong.  I know I will get some controversy over this, but it's the truth.   I hope this helps. 


        Pete and Jean
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« Reply #5 on: January 03, 2007, 02:09:40 PM »

Hello Jerry.

You can install a switch controlled jumper in the side instrument panel to enable the coach and AC blowers.

This bypasses the "no gen" relay. Only weakness is that you may accidently run the battery flat while the coach is sitting by engagaing the blowers with the engine off.

Mine was set-up with a big Webasto inline to the HVAC and the jumper. With a source of 24DC by way of a charger, you get stock style heat without the engine running.

Or, the ability to run the blowers if the alternator system fails and the genset and charger is brought into play.

The coach is 2 hours away, otherwise, I'd go check to see what it is attached to.

happy coaching!
buswarrior
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« Reply #6 on: January 05, 2007, 03:17:29 PM »


Hi;
     Hope it's not too late for you to check back on your post,   but
     here goes.  The belts are called out on pg.8-6 of your parts
     manual.  Part number is  8f-27-3.   (MC7 manual).   the parts
     and all should be the same.  I believe you have a MC-8.
     I had a similar experance.  passing thru Oakland, Ca  I lost the
     generator belts also.  To make a long story short,  I ended up
     using Gates belts,  # XL 7410  from a local auto parts store.
     That was approx 6yrs ago and I am going to replace them
     soon.  They are starting to slip.  I ahave another set of Gates
     belts available when I get time to change them.
                                   Good luck,   Merle

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captain ron
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« Reply #7 on: January 05, 2007, 04:24:21 PM »

Which MCI 8 setups had belts for the alternator/generator? Mine has the gear driven one like my old 8v71. The only belt mine has now that the ac compressor is out is the belt for the squirl cage blower for radiators
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JerryH
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« Reply #8 on: January 05, 2007, 05:54:17 PM »

I did in fact get the belts.
I called MCI Parts who were very helpful.  They gave me the part #8R-27-3.
The MCI price was $10.45 each.  But needed a $100.00 minimum for free S&H or pay $30- for 3 day service, $50+ for next day.
I opted for NAPA which got me the belts the next day.  The MCI did cross reference on their system to #XL-7420 @ $13.43 each.
So I went with $56.94 vs. the $90+

Merle:
Nope, never to late to add to a post -- always valuable information to be learned.

CptRon:
Ours is a '74 MCI with a DD8V71 and a HT-70 transmission (yes, HT-70 ... not 740).
Four belt pulley off the back, accessible from the drivers side rear access door.  Has air tensioner ... pretty easy to make the swap.

Thanks all,
Jerry H.
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buswarrior
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« Reply #9 on: January 05, 2007, 06:09:52 PM »

Hello.

My 1975 MC8 has belt drive, air cooled alternator.

The switch to gear drive, oil cooled came in somewhere shortly after, and shortly before the end of the MC8 run.

Some have retrofitted their earlier coaches, some have left it stock.

Save your 4 place pully for another busnut if you do the conversion, both the engine and the alternator ones.
They aren't getting any more plentiful.

happy coaching!
buswarrior
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JerryH
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« Reply #10 on: January 14, 2007, 07:08:57 PM »

Re-vistiing this question ...

Ok, so here's a question for someone who might know.

The air-tensioner on the 4-belt 24vdc alternator -- there's the quarter turn air valve (same as on the large belted squirrel cage).
There's air feed in, and two out.  One leads to (if I remember) the top of the cylinder, the other leads into (what?) -- a diaphram of some sort?  From it, one line leads to the other end of the cylinder, while the other goes to a relay it appears.

My guess at this point is that (if it is some sort of diaphram) it's stuck, not allowing the air to make it to the cylinder. 

So, anyones thought??

Jerry H.
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buswarrior
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« Reply #11 on: January 14, 2007, 07:59:37 PM »

Hello Jerry.

The belt tensioner is powered both ways: Keeps the belts tight in one position, and pulls the alternator up to allow you to more easily change/replace the belts. That's the lines to both ends of the cylinder, just like a hydraulic ram.

The system is also tied in with a pressure switch to a dash warning light, maybe the no gen light? or maybe low air? Can't remember.  No pressure for belt tension, you get warning light up front, I can't remember what is actually going on with the controls in that Penn switch attached to the rear junction box as to the functioning, just remember what happens, sort of!

happy coaching!
buswarrior
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JerryH
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« Reply #12 on: January 15, 2007, 04:05:20 AM »

Hello Jerry.

The belt tensioner is powered both ways: Keeps the belts tight in one position, and pulls the alternator up to allow you to more easily change/replace the belts. That's the lines to both ends of the cylinder, just like a hydraulic ram.

The system is also tied in with a pressure switch to a dash warning light, maybe the no gen light? or maybe low air? Can't remember.  No pressure for belt tension, you get warning light up front, I can't remember what is actually going on with the controls in that Penn switch attached to the rear junction box as to the functioning, just remember what happens, sort of!

happy coaching!
buswarrior

Buswarrior:
Yeah, the one switch should be "Low Air" ... the "Not Gen" should (I believe) handled not from air, but from electrical output from the alternator.  I am referring to the one device after the one air line off the air valve.  Curious as to it's function.
Jerry H.
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« Reply #13 on: January 15, 2007, 06:03:17 AM »

Is the device you are asking about not a pressure regulator to control the amount of tension on the belts?
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buswarrior
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« Reply #14 on: January 15, 2007, 08:38:40 AM »

From the foggy recesses of my brain this AM...and a schematic...

No air pressure on the belts, the system won't allow the alternator to be loaded, and the low air light will be on.

Somewhat goof proof, eh?

On my '75 MC8, the "Gen Control and Low Air switch" is plumbed into the loop to the alternator belt tensioner.

So, this is where the air pressure is sampled for the low air warning, as well as allowing the alternator to come online once sufficient belt tension (air pressure) is achieved to prevent throwing them off or slipping under load.

Good engineering? Two birds, one stone.

happy coaching!
buswarrior
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JerryH
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« Reply #15 on: January 15, 2007, 01:37:11 PM »

Is the device you are asking about not a pressure regulator to control the amount of tension on the belts?

Stan:
I don't "think" so as this device is on the unloading line of the cylinder.  Pressure regulation I would think would have been on the supply end to the cylinder.
Jerry H.

Quote
From the foggy recesses of my brain this AM...and a schematic...  No air pressure on the belts, the system won't allow the alternator to be loaded, and the low air light will be on.  Somewhat goof proof, eh?   On my '75 MC8, the "Gen Control and Low Air switch" is plumbed into the loop to the alternator belt tensioner.   So, this is where the air pressure is sampled for the low air warning, as well as allowing the alternator to come online once sufficient belt tension (air pressure) is achieved to prevent throwing them off or slipping under load.   Good engineering? Two birds, one stone.
happy coaching!
buswarrior

Buswarrior:

I think I'll look at this intermediate device.
I can't believe there aren't others out there with the same configuration.
Somewhat striking out here.

Jerry H.
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JerryH
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« Reply #16 on: January 21, 2007, 07:16:44 PM »

Feel likes I am (almost) talking to myself in this thread.
But ... the jury is back ...

It's the air cylinder.
I checked the valve ... checked the diaphram above the valve ... nadda.
disconnected the hoses and bypassed the valve to see what the cylinder would do ... it don't DO what it's supposed to do.

So the thought...

When we left Florida and engaged the AC, I figure the cylinder pretty much failed then.  It could no longer maintain adequate tension on the four belts causing them to spin, heat and blow apart.

So that's all I have to offer on this subject.  Now just need to find a replacement.  Anyone know whether you can rebuild them.  I haven't tried to dissect it yet.

JerryH
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« Reply #17 on: January 22, 2007, 07:30:38 AM »

Jerry,
I don't know what the air tensioners were like on the older buses, but the air tensioner on my 96A3 is simple to pull apart.  You can buy a rebuild kit from Luke and easily rebuild in about 1 hour.
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« Reply #18 on: January 22, 2007, 08:16:53 AM »

Hello
    My first post   I have a 72 7 with the 4 belt setup. Before I bought the bus someone replaced the air tensioner system with a solid turnbuckle; not knowing any better I have put 40000 miles on the engine and it has been fine. (the bus air did not work and I removed it;  R12 system )  Having thought about the original bus wiring diagrams system I can offer several reasons why it was setup the way it was. The coach air system use high amperage motors and when the coach is first started if the air is selected on this would put a large load on the alternator before spinup occurs. So the air tensioners needed to be tight before a large load is presented to the generator. THe penn switch in the gencircuit does not let the alternator field energize until about 75 or 80 lbs air is present. This lets the tensioners work as I believe the regulators are set for 65 lbs or so.  Then the alternator can make amps and run the AC system. If you think about a bus in service sitting at the terminal the bus wants to be cooled asap when passengers start to load. THe door is open and the driver wants it cool now.  So the circuit was designed to save the alternator from this high loading before it is ready.  If you do not use the original bus air system then the 3 or 4 large amperage motors are not in use and a solid turnbuckle tensioner works ok especially if the penn switch is working and I wonder if the penn switch is really necessary.  If you extend your thinking the 275 amp alternator is not really necessary without the AC unless you use it to charge your house batteries etc etc.  THe AC compressor had a tensioner on the belts also . If you take that tensioner away remember to seal the air lines. I had a 5a that would not stop because someone removed the ac compressor tensioner and did not cap the lines and that air circuit fed the shutdown cylinder. The bus did not stop and we had to stall it until  the lines were capped...    My opinions are my own and are subject to discussion .  I may not be right and .... i can stand correction....  I am presently working on an L10 mechanical B400Relectronic combo to retrofit into the 7  but that is another topic....     cheers   mike





if 
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Mike Lutestanski   Dunnellon Florida
  1972 MCI 7
  L10 Cummins  B400R  4.625R
JerryH
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« Reply #19 on: January 22, 2007, 05:28:13 PM »

...I can offer several reasons why it was setup the way it was. The coach air system use high amperage motors and when the coach is first started if the air is selected on this would put a large load on the alternator before spinup occurs. So the air tensioners needed to be tight before a large load is presented to the generator.     cheers   mike

Hey Mike,
Welcome to the board!!
You know ... I never thought of that.  You are right.  If the air/heat switch was on and the coach was started, it won't engage until the air is up and tensioning properly. 

And Brian ... thanks, I will call Luke tomorrow.  Looking forward to heat!!

Jerry H.
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buswarrior
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« Reply #20 on: January 22, 2007, 10:08:13 PM »

Hello.

The air tensioner is there so a competent professional driver may replace their own belts at the side of the road without any tools.

Can't do that with a fixed rod to hold belt tension. Also defends against the wrong tension being put to the fixed rod by mechanics or others.

Teenage daughter and I swapped a set in under 6 minutes start to finish, belts out of hold, hatches open, hatches closed, hands washed. Works great to have the assistant down through the floor holding the belts against the engine pulley, while you are outside feeding them onto the alternator. They like to jump one over the other if you do it alone from outside.

The electrical draw reason only works if there is a loss of air prior to start-up. All of our coaches were capable of holding their air for long periods when new, and could again, if we made it our mission to tighten them up. Back in the day, it would all turn on as the engine started.

A good old bus company would instruct its drivers to shut down the AC before shutting down the coach, for this very reason. Any who ignored it, would eventually have to put a set of belts back on...

My vote would be to maintain the air tensioner if for no other reason than ease of roadside maintenance.

happy coaching!
buswarrior

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« Reply #21 on: January 23, 2007, 04:40:14 AM »

Hello:
    I have to say that Buswarriers comments are all on the money.  My experience has been with 4 or 5 buses that are all antiques and suffer from the fallen arches syndrome of leaky beams , failed maintenance, and northeast salt. Never having been a professional driver I do not have the benefit of that experience and training.   I agree that the changing belts with no tools makes alot of sense especially if you are sitting about two feet from the edge of 70mph traffic. 
        I do want to say that every bit of engineering has a purpose even if some of it is forced by regulation . No one does anything for nothing so if you think about it good engineering takes thought and a reasoned process to check beforehand that all the ways the circuits work are what was intended .  Thanks for the info ...   cheers   mike 
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Mike Lutestanski   Dunnellon Florida
  1972 MCI 7
  L10 Cummins  B400R  4.625R
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