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OTR switch “off”, still getting heat from OTR
Driving north out of Florida and into Georgia today. We’ve had the OTR switch in the “off” position for many days; other options are “A/C” and “heat”.
As the sun went behind the clouds and we got further north I instinctively turned the driver’s temp control up. And we go heat. I thought “huh, with the switch off, why are we getting heat”. So I turned the temp all the way up and the air coming out of the left-side driver’s vent was 132 degrees.
Is there a water valve stuck partially closed when the switch is “off”? What about the rest of you OTR/bus air owners. What has been your experience?
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16 Replies
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You can turn system on buy pressing the on button or the plus or minus temp buttons or the fan button
the prevost sheet is not very clear below don’t know why
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Thanks for posting that Peter. But those instructions most be for a fancy bus and we don’t have a fancy bus with fancy OTR controls like that, or at least we haven’t found them yet!
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Sorry Dick but thought it might be the same for yours my fault
Edit. My fault Dick was not thinking of the year of your coach sorry !!!!!!
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I’d love to find something fancy like that on our bus.
I think the operative question is: When the OTR switch is “off”, is the water valve to the driver’s OTR heating cooling completely closed?
When the flip the OTR switch to “heat”, the air does get hotter … but not by much.
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My heat stuck in the on position one time. Even with the fans off the heat was radiating up and blowing us out. Turning the heat on for a while and turning it off “unstuck” it. It has never happened again.
Davy
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I think I have the same type of OTR control. A rocker switch, Heat-OFF-A/C. No heat in the OFF position.
Gerald
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Gerald:
If you have the switch in the “off” position, turn the turn the driver’s temp knob all the way clockwise (highest high), turn the driver’s knob up … you get NO heat from the driver’s vents. Please confirm. Thanks!
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Dick,
Confirmed today. If the OTR rocker switch is in the middle (OFF) position, I do not get heat when I turn up the temp or speed controls. I do get lots of cold air.
Sounds like your solenoid valve for the front heat exchanger is stuck but that does not explain why you can regulate the temperature which is done by cycling the valve on / off depending on temp setting
Does the A/C side get cold?
Gerald
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Hi DIck,
Turns out my switch works the same way. You can get heat in the driver area without turning on OTR heat. Yesterday, I simply had not warmed up the bus long enough.
So, the OTR heat switch is really for the rest of the coach not the driver area. Always something to learn
Gerald
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The A/C side finally gets cold, after Jeff Rowe determined there was an internal problem in the Carrier OTR compressor and replaced it. It gets cold, but some of the owner OTR owners talk about “hanging meat” which I’m not able to do yet.
I played with the driver’s heat rheostate and a digital meat thermometer on the trip Friday from far southern Illinois up US51 and eventually I-39 to Beloit (WI).
It appears to me that what ever controls the heat is an all or just a little arrangement. Once I’ve been running the coach with the driver’s temp rheostate in one position (and presume its “satisfied”) turning it up a very small amount results in a big increase in the temp of the air coming out the driver’s vent. Same for small turn of the the rheostat down if its putting out heat. So it doesn’t appear its mixing air. Nor does it appear that the valve that controls the water flow is any more than a full on or full off; or maybe full on or almost full off (or simply a valve that doesn’t close all the way).
Next summer I might try to run the OTR with everything warmed up and see if I can find the water lines to the front of the coach. I presume that when I flip the OTR switch to A/C, the flow of hot or warm water from the engine to the front of the coach should stop. But that is just my presumption at this point.
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Dick, there is a heat exchanger with hot engine coolant at both the front and OTR evaporator coils. The flow through them is solenoid valve controlled. If they are leaking you are mixing heated air with the cold air crossing the A/C system evaporator. If you want to see if that is the problem shut off the coolant loop and then see if the coach A/C system will cool down as you would expect.
Get the supply and return air temps prior to shutting off the flow, then shut off the flow. I think on your coach the main shut off valve is on the forward bulkhead in the driver’s side compartment just behind the tag axle. Give the coach time for temps to stabilize before taking the readings and take them at the same location so inlfuences like the sun will not affect the readings.
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Thanks Jon! I was planning on a test like that and now you’ve confirmed I was headed in the right direction. Having a place to start looking for the hot water circulation valve might save me as much as 10 minutes to two days of time.
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I think there is a rubber flap and it is a gate valve behind the flap, or somewhere on the forward bulkhead there are some large 90 degree ball valves that might be the Prevost loop. Liberty marked the valves with plastic engraved tags. You probably noticed them when you were in the compartment polishing the copper pipes.
I am not sure if the valve shuts off the forward heat exchanger, but you will be able to determine that pretty quick.
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