MCI Heat Temp. Control

[DavidInWilmNC]

I used my OTR A/C on my last trip.  It works very well; we actually got a bit chilly.  I only used the driver's air for a few minutes while the sun was straight into the windshield.  I opened the right side water valve (next to the engine) prior to coming home so I could regulate the heat.  The air was cold for a while, but then suddenly got hot.  I thought something had happened to the A/C, so I switched on the driver's A/C, and it was still cold.  I eventually stopped and closed the water valve.  I'm not sure if it the temp. control valve was open the entire time or not, as I know it takes a while for the engine to get warm enough to produce heat.  I know the green 'tale-tell' light in the dash would cycle on and off, which I believe is the controller calling for heat.  I can't remember if the light is on when it's calling for heat or when it's satisfied.  Does this valve close when 24 volts is applied to it?  If anybody has any pointers for figuring this out, I'd appreciate it.  I don't mind having very cold A/C in the summer.  I can cycle the compressor on and off with the toggle switch at the control panel, and I believe that the compressor can unload a cylinder or two when less cooling is needed.  I don't think that full-on heat will work well in the fall or winter.  If it is the control valve, can it be repaired or are they just replaced?  Thanks for any troubleshooting or repair tips on this.

David

[Busted Knuckle]

David when the "green light" is on it should be appling a ground to the valve (which has a constant hot 24v) which should open the valve.  I've never had to repair a valve before (not saying that they would never need it), but rather had to find and fix the lost ground, or rewire it after someone had tried to "fix it" and  grounded it ! Not understanding that it is not supposed to be permenatly grounded (easy and common mistake). But one which would make the valve stay open constantly! (hot all the time?) FWIW! BK

[Doug1968]

David & BK,

In searching for some board information regarding the main heat water control valve I ran across this posting by David. Last fall I purchased a 102A3 and I have been fixing minor things on the bus. Recently I delivered the bus to a local Detroit Service Center to have the bus serviced and some oil leaks fixed on the engine. While driving the bus the 40 miles to the service location I found that I could not get the cabin heat to operate? Last year when I bought the bus it was warm and on the drive home I ran the air conditioning and it worked well.

In trying to get the heat to work I found a water valve located in the front r/h bay just as is shown in this posting. The water valve on my bus had been replaced with a valve that is like a faucet with a round handle for opening the valve or closing.

In researching further I found that the original valve is a solenoid style that is opened or closed by a rheostat in the cockpit. I have purchased a rebuilt valve and the valve has one terminal for attaching a wire. The original wire is in-fact hanging in the bay and a ground wire is attached to a ground terminal by the valve. There is no place to supply air to this valve as David has noted in the attached photo.

I assume that if I attach the wire to the valve it will function properly?

I would like to know if there is a way to shut the water going to this valve off so I do not have to drain all of the antifreeze?

Thanks,

Doug

Any information that might help me with this topic would be appreciated.