MCI Driver's AC

[ojgetaway32]

Hello All:

1983 MC9.  I have finally gotten my bus air working properly.  I have two small questions.  First, the Drivers AC is not working.  It gets wicked hot up front with the sun beating on you through that giant two piece windshield.  I have not inspected it or anything at all.  Is there a general consensus about whether or not drivers AC is work fixing?  I know it depends on what is wrong but this is always a great place to start.  Second, on the passenger HVAC, one can direct air out the window vents or out the floor vents.  Should this be changed at different times of the year?  Which is better?  Apply warm air rises and cold air falls pricinpal?

Thanks,

Josh

[buswarrior]

Driver's AC is slaved off the main system.

The simpler things:

Have you got the fresh air damper closed? Defeats the AC if that damper is open or leaking.

Have you got the water valve by your left ankle closed?

By tradition, the floor vents were closed for AC use, and re-opened for cold weather operation. But for a busnut, just getting the air to circulate well will do the job.

For a bunut, what might matter more is whether the ducts have been cleaned out and all the fins on the squirrel cages have been carefully cleaned one by one.

We don't have 11 of the 47 passengers sitting squarely against the sunny side of the coach, with another 11 sitting hip to hip beside that.

happy coaching!
buswarrior

[ojgetaway32]

I have much to learn.

What is the fresh air damper and more importantly where is it?

I didn't know I had a no good son of a %^$^$#ing mother loving hot water valve by my left ankle.  I thought when I shut the hot water off at the engine, it would shut it off everywhere.  Am I wrrrrrr...wrroon....wrong?

Josh

[robertglines1]

I use a 20 inch ceiling hugging fan mounted above driver..moves air great..and is out of isle to be hit by unwary person...also tint above drivers view( About 3 inches) works as a heat shield.Iuse the mirror tint.. you can see thru it but it reflects heat.Above drivers view of site..I have checkes with law enforcement and no problem...I shut off heater feed in back of bus before it leaves the engine compartment,durring the warm weather..them you can use defroster fan to circulate air around you...good luck Bob

[buswarrior]

Damper control is mounted on bottom edge of dashboard, to the left of the steering wheel, by your left knee. Marked for fresh or recirculating air. It is attached to the damper door behind the heat/ac exchangers, in the dash. Take off all those panels and covers, and follow the cable/rod. Often obstructed with rust bits from inside the dash, or rusted solid itself, or the cable is stuck, etc.

The fresh air intake is above the licence plate, in the overhang.

Yes, there will be no water circulation with the valves closed in the rear, but... the stock coach HVAC depends on those valves being open to blend the air temperature.

The AC runs continuously, and has a little heat added to it to maintain temp, otherwise, it gets colder and colder inside.

Assuming it is all working correctly. It is amazing what the last commercial operator might do in a half assed attempt to get it to work with minimum dollars spent, or minimum understanding...whichever...

happy coaching!
buswarrior

[robertglines1]

Makes sense on heat valves...I close because I don't use bus air and have found heat to enter bus would guess bypassing old valves...reduced heat in front of bus when I did...spoke without complete knowledge of heat mixing with ac to controll temp..Bob

[Busted Knuckle]

As long as you're not using over the road A/C turning of the water valves is no problem.
But if you use OTR A/C leave the valves open! It is used by the system to keep from freezing over.
  BK 

[Brian Diehl]

My way is a bit different ...

I run the AC on full blast.  Then, when the inside has gotten to meat locker temps I flip the fan over to heat.  Of course, I have the coolant line to the front turned off and therefore I'm not really heating the bus. I run it on the heat fan setting to circulate this cold air about the bus.  When the bus finally heats up I turn the AC back on until it is cold again.  My wife and girls end up looking for blankets, but I'm very comfortable with these meat locker temps!  All the while I'm never using any hot coolant at all, just circulating air or chilling the air.

[ojgetaway32]

Okay, you guys are all killing me.  Somebody tell me what to do as far as shutting the water off etc.  The windshield tint is a great idea but I wanna know what to do about running the AC properly.

[bevans6]

To run the MCI OTR AC properly, you put the switch in AC on, set the temp dial to where you want it, and the system does it's thing.  What I understand happens (my manual has some missing pages in this section) is that  what it does is run the AC at full blast continuously and add in heat from the heater to balance the  temp to where you want it.  That balance depends on a fully functioning heater system with all the valves turned on (but the drivers heat can easily be turned off independantly), the thermostat temperature sensor that lives in the cold air return on the passenger side air duct, and the electric water valve (in the rear engine passenger side bar).   All those gubbins and some relays work so that the hot water is cycled on and off by the electric water control valve to balance out the AC cold air.

Like I said, that's how I think it works, but since I took the bus OTR AC out of my bus, I don't know for sure.

Brian

[ojgetaway32]

Great Stuff Brian.  Thanks for the info.  I had no idea it depended on warm water to run properly.

[RJ]

Ojgetaway --

FYI, the operation of the MCI OTR HVAC is exactly the same as GMC has been doing in their automobiles for years.

When they started putting AC in OTR coaches back in the late '40's, they (GM) came up with this simple system.  It was later "downsized" for automotive use as A/C became more popular in the late '50's and early '60's.

MCI simply copied what GM did, because it works, and works well.

As Buswarrior said, the main coach HVAC system has to be on in A/C mode for the Driver's A/C to work.  It's completely automatic - with the main A/C on, simply turn on the Driver's A/C switch.

Do you still have the dashboard fan?  Using it helps, too.

If you don't have one already, you seriously need a copy of the Shop Manual for your bus .  The three (or four) essential books every busnut should have is the Shop Manual, the Parts Manual, an Operator's Handbook, and, optionally, the appropriate Engine Manual, be it a Detroit or SOB.  You'll find that an awful lot of your questions can be answered simply by reading "DA BOOK!"

FWIW & HTH. . .