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Old 11-15-2023, 10:10 AM   #1
Almost There
Join Date: May 2021
Location: Santa Barbara, CA
Posts: 75
Inverter fan constantly running, no loads

Inverter fan keeps running constantly. Just started doing this yesterday. Zero loads being pulled thru inverter. Wired in remote installed on wall panel doesn't turn it off anymore like before. It doesn't respond at all. When I turn remote on/off, inverter fan slows slightly upon power on, and then.back to normal within 3 seconds. Turned all breakers off, still kept running the fan. So, breakers off, no loads at all being pulled, remote turned off....and still it runs.

Fan ran straight for 20 min until I pulled fuse from battery bank to inverter. Typical fan time is 30 seconds-2min? This is WAY too long and abnormal. When I put fuse back in, immediately the inverter fan kicked on, no loads.

Causes? What causes an inverter fan run away like this?

Bad battery? Bad inverter fuses?

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Old 11-15-2023, 12:46 PM   #2
Bus Crazy
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Join Date: Jun 2023
Location: South Carolina
Posts: 1,008
Year: 1995
Coachwork: Thomas
Chassis: International 3800
Engine: T444E
Rated Cap: 29
Some inverters have a temperature monitor inside of them, and fan control is usually controlled based on the temperature profile. All of these things you will not be able to touch or change.

For some reason the monitor thinks your inverter is likely hot and needs to cool down, so it's never shutting off. This is likely due to a "Bad Sensor" thinking it's hotter than it actually is because it is broken, or something is constantly drawing from your inverter and it's never cooling down past the temp that would shut off the fan.

Unfortunately there is no easy fix for this kind of thing. It's a PCB board issue, and even if you were good at kind of thing like I am, I'd still have a hard time hacking it or disabling it because they are too integrated now days. Sometimes the sensors are literal chips on the PCB, and even if you could identify that it was a chip, and ordered a new one, the replacement one may not be programmed properly to work on your board.

So basically the only options you have are to live with it, or dismantle the inverter and try to identify a temp sensor (if it's even easily identifiable) and see if it is something you could replace. Some sensors come in the form of a wire with a flat tab on the end, others are built into the chips themselves. If it's a wire form you can order them easily enough and replace, but if it's a chip likely not and have any kind of success.

Due to the nature of this application, if it truly is hot though, and the sensor is not the issue, your inverter is on it's way out or being used too much and it's doing it's job and not on the way out, but you are using too much power keeping it hot constantly.

Disabling the fan is not a good idea especially if the inverter is in a mobile vehicle as you don't want a fire to start in such an environment setting the whole home ablaze. While they are costly, it's worth it to just replace the whole inverter if you cannot identify a bad sensor and cannot afford to live with the fan noise.
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Old 11-15-2023, 02:22 PM   #3
Bus Nut
Join Date: Jun 2015
Location: Toledo OH
Posts: 823
Year: 2006
Coachwork: Thomas
Chassis: MVP-EF
Engine: Cat C7 + Allison 3000PTS
What kind of inverter?
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Old 11-17-2023, 05:51 AM   #4
Join Date: Mar 2022
Location: Middle TN
Posts: 157
Year: 2008
Chassis: IC RE (PB30500)
Engine: Maxxforce DT
Possible to find the wiring to that fan and cut into it? That way you can install a secondary temperature sensor in your invertor that would interrupt the constant power to the fan when not needed.

Just an idea.
2008 IC RE 40ft w/ Maxxforce DT and Allison 3000 PTS for fulltime living w/ a family of four.
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Old 11-17-2023, 07:59 AM   #5
Bus Geek
Join Date: May 2009
Location: Columbus Ohio
Posts: 19,007
Year: 1991
Coachwork: Carpenter
Chassis: International 3800
Engine: DTA360 / MT643
Rated Cap: 7 Row Handicap
one of my inverters runs its fan pretty much anytime the temp is above 75 in the bus. the only time I dont hear it is when I first turn it on and start up on a cold morning..

its there for a reason.. adding your own sensor is going to affect its overall temperature.. no way to know if it hurts the unit or not.. and maybe your inverter has a small heat sink so they just run the fan all the time to keep it cool..
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Old 11-17-2023, 01:30 PM   #6
Join Date: Sep 2016
Location: Amarillo Tx
Posts: 142
Year: 1999
Coachwork: International
Chassis: 3800
Engine: T444EIEIO
Rated Cap: 8 window?

My samlex inverter fan ran almost constantly until I found switching the inverter settings from grid priority to battery priority. Battery priority seems to conserve power consumption by the inverter.
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Old 11-17-2023, 02:55 PM   #7
Bus Crazy
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Join Date: Jun 2023
Location: South Carolina
Posts: 1,008
Year: 1995
Coachwork: Thomas
Chassis: International 3800
Engine: T444E
Rated Cap: 29
Another idea is if noise is the only concern is to buy a Noctua PC fan. They are dead quiet. It wonít help the battery drain but if itís going to run all the time you could wire one of those in just to kill the noise at least.
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