[Mark]

Mark,

I have no experience with an H, but I had a non-slide XL with OTR.

Liberty has made that vintage coach for a long time and I am comfortable in saying the A/C distribution is pretty good back in the bus. The dash and house are two separate systems using two separate blowers and ducts. The house has air distributed along the base of the windows and the return is under the sink if that is on the driver’s side. If your filters are clean, and you do not have any obstructions to air flow your cooling at the ducts in the house should be ample and should work very well.

[Corey]

Let me check the filters next then. Hopefully they are totally plugged up. Like I say its the mid coach area that has absolutely NO volume. Kind of like a mouse blowing across an ice cube. The rear of the coach has plenty….

[Archived]

I think that there should be a rehostat or 2 speed switch to control the fan speed,is it turned up to high?

[AL]

Jack,

I only have the one fan on the dash. It is, of course, turned all the way up. The rheostats on the panel for the panel air and bus air are both turned to full cold….

[Archived]

Are the ducts made from a material which might collapse or develope a leak at a seam or redirection in the run to the vent openings? I had a similar experience with a house vent.

[Andy]

The Liberty ducting is not tubes or hoses, but is a plenum made by having a passageway for OTR air such as a wall panel that stands off of the outer shell so the air can pass through that area the entire length of the coach.

If the coach had a remodel and the work did not reflect the need to maintain air flow that could be the problem. Along the length of the coach on both sides (as in a non slide coach) air from the evaporator pressurizes both plenums and air flows through “screens” in the wiondow sills and along the top of the backsplash over the sink counter.

[Archived]

Yes Jon that is exactly how mine is and I cannot see anywhere in the work orders or logs where any alterations of any kind have been made that would affect the systems. BTW the filters were clean and new (Prevost changed them).

Mark

[Archived]

Mark Have you looked in the evaperator bay (drivers side) to see if the duct connections have hole or loose?

Darrell

[Archived]

There are no ducts of material that can get a hole in it.. The evaporator fan draws air through the filters from inside the coach, and the air past the evaporator travels through passages created by Prevost that direct the air up into the runs that go fore and aft on both sides of the coach.

[Archived]

I had a 2001 Marathon XLII that I was the third owner of and when the coach was converted Marathon failed to re install a rehostat when they reassembled the dash,this rehostat controlled the fan speed of the coach blower(not the dash).The second owner also told me that he had an alternator failure so there was an extra alternator that was a 75 amp 24 volt unit.After I owned the coach for a month or so the OTR air would not keep the bus cool on hot days,so I investigated and went to the Prevost wiring and found that the rehostat connected to wire 428 and it was not there so I ordered a rehostat from Prevost.I installed the rehostat and then on the next trip I had the 75 amp alternator fail,Marathon had failed to wire the bus air correctly,Marathon uses the 270 amp alternator to charge the house batteries and installs a 75 amp alternator to charge the coach starting batteries and they rewire the bus air to the house batteries but they failed to do this on this coach,so the 75 amp alternator was overloaded and HEAT got it.I was floored that the 2 previous owners did not comprehend that a 90,000 BTU bus air unit would not cool the coach and they did nothing about it.To Marathons credit they did rewire the OTR for free.Even though we think that everything is working properly just verify that the fan has the correct DC voltage or it will not be performing at the correct rpm.

[Archived]

Am I readig this right, Prevost when facing a customer with an AC OTR problem did not even check the air filters? Sounds incredible to me. Start with the simple and work toward the more complex contibuting parts. Sounds like Prevost did the job in reverse, maybe they didn’t know there were air filters in their OTR system.

[Archived]

On H-model coaches, there are vinyl boots that attach the blower outputs to the two sections of ductwork that go to each side of the coach. H’s also are more complicated, looking at temp sensors in the return air that comes from the top entry step and from the return air that is mid-ship, as well as a humidistat, and feed all this to a logic board that then controls the compressor and variable speed evaporator fan. I am surprised Prevost did not take care of the issue, though, especially in Texas, the hottest of temperatures Prevost facility lol.

Converters sometimes, in an attempt to make up for the outlet space they are covering up, do effect the air distribution by cutting too large a hole in the duct midship, too close to the section coming from the blower, dropping the static pressure and resulting in uneven distribution at the vents. You may want to try blocking small vents off midship in the bath area and see if this helps your situation. Don’t block off too much at at time though. Let us know the outcome.

[Archived]

Oh, one more thought…the bus temperature is regulated by the controller opening and closing a hot water valve to a heater core in line with the evaporator coil. Sometimes in H’s it really helps to shut off the coolant line to this heater core to prevent hot water tempering. If the valve seat is leaking by or sticking open, this would also help heat things up. We have gotten in the habit of calling this a “summer/winter” valve because closing it when you need max air conditioning really does help in most cases.

[Archived]

Good point Ben, I do this on my H for the dash air, turn off the coolant loop.

[Ronald]

Wouldn’t the hot coolant circulating have the same effect in an XL or in my case XLII ?