[Don]

Colt

Marathon put’s 2 fans in your inverter box with a thermostat. One fan pulls air and one pushes it out. Depending on where your at it could run longer than usual.

Our buses are set up a little different but in the swamps of TX in 105 temps and 95 humidity mine ran until 2am one night.

I don’t know what the cut in and cut out tempature is because I have only tested mine with a hair dryer.

Later

bv

[Dick]

Same as Bernie with mine, they run long when hot. I checked it just this week while roasting here in FL and the inverter temps were 108 and fans humming.

[Archived]

Colt, I defer to the Marathon gurus when it comes to describing how you are set up. But I have perhaps a different spin on inverter fans. I would leave them on continuously.

First, all inverters should have internal fans that cycle on and off as needed based on temps inside the inverter case. I cannot tell you how to know they are functioning properly, but I can tell you that when the inverters are “working” the fans should cycle on and off. If they do not the inverter can be exposed to high temps and high temps will shorten their life. Because they have internal fans that draw fresh air in for cooling, you can expect they are also drawing in dust, lint, and airborne stuff that over time is going to end up inside the inverter case and affect it.

So as part of the long term maintenance events consider opening up the covers of the inverters and blowing out or vacuuming out the collected debris.

Checking the internal fan operation is something that should periodically be done. I am going to guess that loading the inverter as a charger or using it as a loaded inverter will work to kick on the fan(s). Turning on all the 24V ceiling lights on my coach kicks on the inverter fans after a while.

Now regarding the fan used to cool the inverter bay. If your bay in which the inverters are mounted is not ventilated the internal inverter fans may cycle on, but there is not much benefit if the bay is hot. So the external fans should be set up to keep the bay cool. On my coach the fan runs continuously so the bay itself is always getting fresh air. I know some are controlled with a thermostate so the bay temperature determines when the cooling fan(s) are turned on, but however your coach is set up you need to keep the bay cool otherwise the internal fans are just drawing hot air through the inverter and cooling is compromised.

[Jim]

The cooling fans on industrial inverters run continuously. Our techs often find bad fans on trouble calls. Most industrial UPS/inverter manufacturers recommend fan replacement on 5 or 10 year intervals.

[Archived]

Thank you for the info and suggestions.

The fan is running continously, even when it cools off at nignt. This condition developed recently…I know that the fans have not run continously in the past.

I am going to remove the panel and take a looksee.

[Archived]

Don’t forget, you should have fans to cool the bay, but fans internal to each inverter. All need to be working correctly.

[Richard]

I took the panel off. The internal fans for both inverters are running constantly. There is a fan on the left side of the bay in the inverter compartment. It is connected to sheet metal ductwork, drawing fresh air (or maybe heat?) from somewhere. This fan is not running.

I will be at Jeff’s soon, so I guess I will have him check it out.

[Mark]

The bay fan(s) are thermostat controlled as are the internal cooling fans for the inverters.

[Archived]

If both internal fans are running it means the thermostats have both failed closed (how likely is that?) or the bay is too warm or they are really heating up those inverters. It is all worth checking out.

[Paul]

Hi Guy’s

I have been reading your posts since we purchased our 1998 Liberty XL45 back in April. So far my time has been spent whith updates and minor repairs taking it on 1 small bite at a time. We are not new to coaches but this is our first Prevost. This thread cought my attention as I am in the process of diagnosing the battery bay cooling fans.

I am not sure how Liberty wired these and even thought they may have been someones modification until I saw this thread. The Liberty electrical wiring book makes no mention of the fans or a reference to a fuse circuit #. I thought the 1 operational fan ran continiously until I shut the inverters off for a few days. So it appears that there may be a thermostat located somewhere? The 2nd fan which is not working appears to have a cut cable running behind the entertainment center in the 2nd bay. There is no power to the feed side of the cut cable.

I was wondering if anyone is familiar with this model and might be able to give some guidance as to where the thermostat would be located, if each fan runs on it’s own thermostat and what circuit numbers to looks for in the fuse panel for a possible blown fuse?

Thank you

[Jim]

Roger,

My 01 Liberty had the inverter compartment and entertainment center cooling fans hard wired to the inverters. You could not shut them off unless you killed the inverters and they ran 24/7. I installed thermostats, but Jon is going to have a different take on this. Either way, they run all the time with no way to remove power to the fans unless you install a thermostat.

Jeff is the expert, so he’ll jump in here I’m sure.

[Rodney]

Tom,

I believe I have confirmed your comment that the fans are hard wired to the inverter. Tonight I checked the bay fan on the inverter side of the coach and it was running. No heat in the bay as the inverter chargers were off and and no loads in the coach. When the circuit breaker on the main power panel in the coach was turned off for charger line 1, the fan also shut off. Most likely the inverter circuit breaker was off when I previously observed the fan not running. Therefore no thermostat.

There is still the issue of no 110AC power going to the 2nd bay fan behind the frig due to the severed cable. Hopefuly that line is fused and when the cable is repaired a new fuse will get it running. Any idea where that fuse might be located? I do not see it in the manual.

[Dick]

Great discussion. I have looked on my 90 Marathon conversion and I can’t locate any fans beyond the fans that are on the inverters themselves. Anyone else with the same year of Marathon conversion have fans that cool that bay. My inverters are in the second bay back from the front, behind the generator location.

[Archived]

Roger,

As you learned you inverter fan in the electric bay is set up to run continuously. It is powered by inverter 120VAC output so regardless of whether you are on shore, generator or inverter power, as long as there is inverter output the fan in the bay will run.

However, each inverter has an internal fan and when the inverters are working, regardless of power source they cycle on an off as required to cool the inverter. They are critical and need to be monitored. All inverters will generate heat and keeping the bay cool only insures the internal fans will have a cool air supply.

Adding a thermostat to the bay fan is a personal choice. My preference is to allow it to run continuously.

[Bill]

Jon, Tom

Thanks for your feedback. I have a clear understanding of how the external bay fans operate now. I have also confirmed that each inverter internal fan is functional under load. I have no interest in adding a thermostat to the external fans as I can shut down the inverters to reduce parasitic loads when in storage.

I do need to trace the wiring to the 2nd bay fan to get it working again. It must have a fuse somewhere? I wil start by removing the shelves above the inverters and follow the wire that connects the functional fan. That may give me an idea where the non-functiona fan is powered.