Bus won't air up

paul102a3 · February 13, 2010, 03:48:26 AM

The bus, 1988 102a3, is in Ohio buried under a foot of snow and won't build air. Started the bus yesterday and the air pressure built up to 50 PSI then stopped. Fanned the brakes a few times and the pressure dropped to zero and that's where it sits now.

How do I figure out what is wrong.

A new AD 9 and governor was installed in September and the air system has performed perfectly since then.

Any thoughts.

robertglines1 · February 13, 2010, 05:16:18 AM

prob ice somewhere in system.around compressor.wait till warms up...or put heat to that area..drop light or small heater.if compressor in rear of engine under floor..pull up hatch and add heat..good luck..little moisture or thickened oil in air system I know there shouldn't be any oil there but the world is not perfect...heat will prob do it...mabe even engine running heat

RichardEntrekin · February 13, 2010, 06:23:48 AM

Does it have auto drains on the tanks? If so look for ice in the drains?

Also look at blow off valve, either at compressor or air dryer.

Sounds like ice to me. Did you have the opportunity to walk around and listen?

Jerry32 · February 13, 2010, 07:07:43 AM

Plugin your block heater. that will warm it up. Jerry

gus · February 13, 2010, 04:14:41 PM

How will a block heater warm the air system?

Jerry32 · February 13, 2010, 04:54:25 PM

the compressor is connected to the engine so engine warm heat radiated around the engine compartment and thaws frozen spots. Try it you'll like it Jerry

Bill B /bus · February 13, 2010, 06:26:18 PM

You've got ice in the air compressor discharge line before the air drier. You need to heat the engine compartment to provide enough warmth to keep the air warm until it clears the air drier. Best way is to run the engine to operating temperature. If you can break it out of the snow then a nice long ride will clear up your problems. The above is my personal experience. Alcohol will work wonders but is not really good for air drier dessicant.

Good luck
Bill

John316 · February 13, 2010, 06:34:30 PM

Just be very careful if you do use alcohol. If you have a heater on the air dryer, the alcohol can get ignited. If you use alcohol, add it after your dryer, if your dryer has a heater. A charter place in-town had one bus burn to the shell, because of that.

God bless,

John

James77MCI8 · February 14, 2010, 06:51:25 AM

Block heater, warmer temperatures and patience and everything will be all right.

gus · February 14, 2010, 04:30:09 PM

Jerry,

Never thought of it that way. I was thinking about ice in the system downstream of the engine compt since it started when he fanned the brakes, but it is a good point.

buswarrior · February 15, 2010, 09:30:14 AM

Hello Paul.

Did you connect the heater wire for the AD9?

Do you get air out of the discharge muffler drain in the curb side engine access?

Don't put alcohol anywhere for now.

Don't start shooting the shotgun blindly until we get some diagnostic work done.

It will simply re-freeze after wild machinations, and you still won't know what was frozen, or what to do to fix it, as the unfrozen moisture gets to travel until it freezes again someplace else.

Let us know.

happy coaching!
buswarrior

paul102a3 · February 16, 2010, 04:24:59 AM

BW, the heater wire is hooked up for the dryer so I assume that is fine.

The situation is still the same. We did run the engine for quite a while so if there was ice in the lines in and around the compressor, I suspect that would have melted. I think BW has hit the nail on the head and what ever moisture is in the lines is moving down the lines and refreezing.

I think I will wait until it warms ups before I do anything more.

Is there any harm in running the engine under this situation? Will I damage the compressor if the air lines are blocked?

Thanks

buswarrior · February 16, 2010, 07:01:05 AM

Waiting until it warms up doesn't solve the problem, let's get all these questions answered so we can find out what's wrong and get you fixed right now, and the rest of our viewers can learn something.

Don't run the engine except for diagnosis purposes.

If the compressor drive is broken, where are the broken bits? I doubt it is broken, but...

As it is now, you probably have no way to control the compressor, and it will keep pumping and pressurize what it can to as high as it is physically capable of pumping, and there is no safety valve in that part to keep it under 150 lbs...

So, the check list we need answers to:

1) Still no air pressure showing on the gauge?

2) Confirm or deny that there is air at the discharge muffler drain in the engine room while the engine is running. If there is air, then the governor and compressor are ok. If not, shut it down, more detailed diagnosis is required.

3) Confirm that the heater wire at the air drier has power. If you took it off a stock location, that location is only powered when the coach stock HVAC switch is turned on. Got ground?

4) If we are still non-functional, aim a heater at the air drier, bottom end, heat will have to get into the middle of that mass, so it will take a while, depending on whether you can get the heat to the metal, or if the wind is taking it away. Do not underestimate the power of the wind to take all the heat away if you don't get it well blocked on three sides.

After that, you'll have air... until it freezes again.

5) Run until air drier blows off, pump down the brakes and get it to cut back in, cycle a few times. Then, pump it down once more and shut down the engine while the air gauge is climbing. You'll be set to freeze up in a functional condition, instead of the way you are now. Shut off the engine with the compressor cut out, it'll stay that way until spring... just like now.

The heater wire is critical, either you have no power, or the heater is shot. Put a meter to the heater and check for the correct resistance. Again, got ground? If no power, just bypass everything and run a length of wire directly from a known source, down the outside, under the coach, across the snow, leave the existing wiring problem for later.

let us know!

happy coaching!
buswarrior

buswarrior · February 16, 2010, 07:07:34 AM

small addition, you can try to check the resistance of the air drier heater from the top end of the wire...why crawl under there if we don't need to?

Confirm power at the top, if there's power, then check resistance from the top.

My money is on there being something wrong with the air drier heater and/or it's wiring. You'll get no power at the top, or if you get power, you'll get no resistive reading.

happy coaching!
buswarrior

paul102a3 · February 16, 2010, 07:13:03 AM

BW, Thanks for all the info. One question has been answered by your post, the HVAC switch is out of the system right now. The switch went bad, blower would only come on in AC setting not in the heat setting. Replacement switch was ordered from MCI but they sent the wrong one.

Once the new switch is installed, we will check power to the heater and follow the next steps.

I'll keep you all posted.

Thanks