light on dash?

[platinum mci]

OK I have the 1983 MCI 9 and on the dash where the illuminating lights are for the brake light and a/c and stuff there is a light in the lower left hand corner that turns on intermittently.  The light that illuminates says heat.  what does this mean?

[Hi yo silver]

It just means your bus heat is on.  Without going out in the cold to fetch my manual, I can't tell you specifically what initiates the indication, but I do know that it does serve as a monitor regarding your bus "cabin" heat.  Someone else with more experience will chime in with more specifics, I'm sure. Hope this helps.
Dennis 

[platinum mci]

helps alot thank you

[Jriddle]

In the book I have if light glows green heating system is on. I would like to know what activates this light? My light sometimes flashes off and on at times. When I bought the bus I had my daughter with me on the return trip. She tried to use the half A@# installed video system and smoke started to come from one of the monitors. Because of this short the heat light was flashing off and on. I have removed all the video system and believe all the electrical problems have gone away. Is it normal for this light fade away and come back on. Hope I don't have anymore shorts. The flashing I see now is very much different than when I had a direct short.
John

[Kwajdiver]

I would open the outside panel, (drive side), look for anything loose or broken. Don't have my book with me, but that's were I would start.  Guessing you have checked the heat on/off switch?  What happen when you turn this on and off.  When the switch is on, does the light stay on?

Bill

[Jriddle]

Thanks Bill
I will start there I assume this light should stay on an not fade away. I will look for a loose connection.

John

[Busted Knuckle]

OK guys bear with me here as my MCI memory is sorta fuzzy, since I spend my time mostly on Setra's these days. But that light indicates that the coach is calling for heat, it does not necessarily mean the heat is "ON". What happens is the coach temp sensor senses that it is cooler in the coach than it is set for. So then it triggers a ground relay and completes the circuit for the light on the dash & at the same time sends a ground connection to the water flow valve in the front bay up under the coach floor next to the "utlity chase" on the curb side. (it's got a little plastic or fiberglass cover over it.) Now if all is working as supposed to then the water valve opens allowing hot water to flow forward to the heater coil and the drivers defrost coil. Now it is normal for it to flash on and off as it nears the desired temp and keeps it there if it is indeed working correctly.

NOW the disclaimer! I am not 100% positive on these facts as it has been serveral yrs since i had to work on an MCI heat system. But I have worked on them in the past and even though my memory is as fuzzy as my face, this is what I recollect! Now having said that I am NOT an expert on it, but I did stay in a Holiday Inn Exrpess not to long ago! 
  BK 

[buswarrior]

BK has it nailed.

No worries, the light goes on and off to regulate the temp in the cabin.

happy coaching!
buswarrior

[buswarrior]

Ooops, it also goes on and off regardless whether you have the HVAC turned on or off.

happy coaching!
buswarrior

[ilyafish]

when i picked up my mc9 and was driving it home i was bugging out about the heat light thinking it meant the engine was getting too hot or something....but yea, all it is is it regulates the cabin temperature. 

from what i understand, and please correct me if im wrong, but it appears that the dial on the left that regulates colder or hotter, instead of mixing cold and hot air to achieve the desired temperature, it appears that it will blow out bursts of both, one more than the other depending on what temperature setting you have it at.  very unnoticable when the air is ducted through the standard wall panels, yet extremely obvious when you are driving around with the 2 vents uncovered haha.

and yes, whether or not the OTR air is on or not, the heat light will continue to go on and off, because it is not triggered to the on/off switch for the air, but instead to the temperature dial.  if you turn the temperature all the way down to cold, you will find the heat light stays off, turn it up all the way for warm, it stays on.  and anywhere in between it will go on and off.

please correct me if im wrong guys, but that is what at least i have come to conclude

[buswarrior]

Yup, you got it.

The system regulates by allowing a certain amount of hot coolant into the heat exchanger, little bursts once the coach is warm, so that the temp in the cabin remains fairly constant. A little burst every so often, according to the temp sender in the return air, and all is well with the paying customer... or she who will not be disobeyed....

the air flow is constant, the amount of hot water flowing in the heat exchanger is the variable.

Pull the wire off the heat valve just for fun and see how quickly you roast...that system has some massive capacity to heat the coach!

happy coaching!
buswarrior

[Jriddle]

Thanks for the good info. While I had the floor torn out I saw a temp. probe in the return air duct. I assume this regulates the valve and and light.

John

[Kwajdiver]

I've had this bus for two years now.  I'm still learning stuff.  Where in the duct is this temp sensor?

Bill
Raining in Gulfport, Florida

[Jriddle]

Bill
On the left side in the front bay next to the electrical box. There is a panel that you can remove with probe. This is where it is on my bus it is a 1984 MC-9.

John

[platinum mci]

I want to think eveybody for all the help, and advice!!!