RV Exhaust Fans Not Working With 11 Volts at Wiring

[pipepro1]

Both of my fans weren't working I installed 1 new fan and it doesn't work although I tested before installation was complete with a battery charger it worked. The one I pulled out and replaced still works. (I wish I would have tested it before I replaced it.) One existing fan didn't work even with the battery charger, my bad I left it running and forgot about it because of the summer heat as the RV sat idle. I checked the interior fuses and did find a fuse blown. I replaced it but nothing yet. Some fuses when I pulled them to check a red light came on till I plugged it back in. What does that mean?
I tested the wires and had 11.04 volts. I've had this problem on my last RV but I can't remember how I fixed it. Memories get foggy at my age.

 

[bigbAZ]

The red light indicates a blown fuse, or, as you found out, a removed fuse. (There must be a load present on the circuit for the red light to light up)

11 volts is pretty low. Did you measure between + and -, and also between + and a metal part that is attached to the frame? Have you tried plugging the RV in? Maybe it's battery time?

If possible, run a jumper from your battery - and see if the fan runs from the + and the jumper.

 

[CharlesinGA]

MaxxAir fans? MaxxAir fans have a limited voltage range. Earlier ones worked on about 10 to 14 volts, but with the popularity of Lithium batteries and solar panels, they were getting the boards burned up, so instead of widening the voltage range, MaxxAir chose to shift the voltage range upward, making the lower limit about 11 to 11.5 and the upper limit about 15 to 15.5 volts. Too low of a voltage, they won't work, too high voltage, the circuit boards get blown. The other issue is that the boards get wet and damaged because MaxxAir chose to not coat th boards with a conformal coating.

People who have been most successful with MaxxAir fans have coated the boards with conformal coating (mask off the electrical terminals) and installed a miniature buck/boost transformer in the 12v DC supply to the fan.

 

[pipepro1]

The red light indicates a blown fuse, or, as you found out, a removed fuse. (There must be a load present on the circuit for the red light to light up)

11 volts is pretty low. Did you measure between + and -, and also between + and a metal part that is attached to the frame? Have you tried plugging the RV in? Maybe it's battery time?

If possible, run a jumper from your battery - and see if the fan runs from the + and the jumper.

I did measure between the positive and negative. I just got new batteries 3 months ago. I did find one fuse blown but no red light so I guess nothing was energized on the circuit. The rig has been plugged in as long as it has been idle.

 

[pipepro1]

MaxxAir fans? MaxxAir fans have a limited voltage range. Earlier ones worked on about 10 to 14 volts, but with the popularity of Lithium batteries and solar panels, they were getting the boards burned up, so instead of widening the voltage range, MaxxAir chose to shift the voltage range upward, making the lower limit about 11 to 11.5 and the upper limit about 15 to 15.5 volts. Too low of a voltage, they won't work, too high voltage, the circuit boards get blown. The other issue is that the boards get wet and damaged because MaxxAir chose to not coat th boards with a conformal coating.

People who have been most successful with MaxxAir fans have coated the boards with conformal coating (mask off the electrical terminals) and installed a miniature buck/boost transformer in the 12v DC supply to the fan.

The one I removed and replaced was an OEM so I don't know the make or model it had a temperature control on it.

 

[Kirk]

Some fuses when I pulled them to check a red light came on till I plugged it back in. What does that mean?

That means that it sees an open circuit. It would be the same whether the fuse has been removed or if the fuse is blown, or open.

(There must be a load present on the circuit for the red light to light up)

This is not correct.

I did measure between the positive and negative. I just got new batteries 3 months ago. I did find one fuse blown but no red light so I guess nothing was energized on the circuit.

Blown fuse indicators typically consist of an LED or warning light connected across the fuse. When the fuse is intact, current flows through the fuse, and the indicator remains off. If the fuse blows or is removed it sees a voltage, causing the indicator to illuminate, signaling a blown fuse. You can easily verify how that works by measuring the voltage across a good fuse and you will read 0 volts, then remove the fuse and measure again and you will read the supply voltage.

 

[bigbAZ]

That means that it sees an open circuit. It would be the same whether the fuse has been removed or if the fuse is blown, or open.

This is not correct.

Blown fuse indicators typically consist of an LED or warning light connected across the fuse. When the fuse is intact, current flows through the fuse, and the indicator remains off. If the fuse blows or is removed it sees a voltage, causing the indicator to illuminate, signaling a blown fuse. You can easily verify how that works by measuring the voltage across a good fuse and you will read 0 volts, then remove the fuse and measure again and you will read the supply voltage.

I guess I got mixed up on that. I have the ATO fuses that light up when blown in my Jeep but I noticed when the brake fuse blew the light didn't light up unless I was pressing the brakes so I thought it must feed back from the load, but I suppose it could also mean the brake switch is before the fuse

 

[Kirk]

the brake fuse blew the light didn't light up unless I was pressing the brakes

That could depend on where the fuse was located. If it is after the switch, there is no power to the fuse to cause the light to turn on.

 

[bigbAZ]

That could depend on where the fuse was located. If it is after the switch, there is no power to the fuse to cause the light to turn on.

The wiring diagram shows the power originates at the fuse, then hits the brake light switch. I had to look this up because I couldn't understand how the LED could possibly light up without a complete circuit thru the load. Turns out I am correct about the ATO fuses, but the ones on the RV panel must be wired differently in a way that allows a complete circuit without a load. The LED must be grounded on one side for that to work.

 

[John From Detroit]

I tested the wires and had 11.04 volts. I've had this problem on my last RV but I can't remember how I fixed it. Memories get foggy at my age.

Something that happened to me and you sure nailed the memory.

One of the things I installed in my RV was a "RIg-Runner 40-12
This is a 40 amp 12 volt "power strip" 10ga wire direct to the batteries.
Well nothing plugged into it worked, all fuses tested good (not indicated but actually tested)
and as I recall about 11 volts on the input connector.. 13.6 at the batteries (Plugged in on float)
So I started seeing what I could see.....

Grabbed my favorite 12 volt test device, an automotive test light.. DARK = Bad and dark it was
(Bright at the battery end)

Followed the wire I mean why was one end bright and one Dark?

Found a "Bulge" Mid run. yes Mid run.. Sliced into it and all copper oxcide. Well bit of excess wire was used (Some slack) so I sliced back to clean copper.. Some heat shrink and solder and everything worked 100%

I was surprised to find the problem MID RUN.. Usually that kind of thing is at one end or the other.

No that I'm in the apartment that same Rig-Runner still powers some of my Ham Radio Rigs and a couple other things here in the apartment. Part of my "Power fail backup" system.

 

[Kirk]

The LED must be grounded on one side for that to work.

That is true. If there is no return side of any electrical device it can't work. Typically an automotive fuse supplies more than just the brake light circuit, but if that is the only thing that it supplies, then you would need to step on the brake for the fuse indication led to light.

I was surprised to find the problem MID RUN.. Usually that kind of thing is at one end or the other.

What you had was effectively a resistance in the wire, which can and does happen, but not often. When that happens, the voltage to the load it supplies will be shared with part of it dropped over that bad spot in the wire and the remainder on the load it is supplying. If you open the circuit at the load end, then it will still measure the supply voltage because in an open circuit there is no load loss at all and so as long as your voltmeter is measuring between some point that connects to the positive side of the supply and the return or negative side, the voltage will be the supply voltage but as soon as there is any current flow that with change.

 

[John From Detroit]

What you had was effectively a resistance in the wire, which can and does happen, but not often. When that happens, the voltage to the load it supplies will be shared with part of it dropped over that bad spot in the wire and the remainder on the load it is supplying.

Yes I know.. I knew from several things there was a High Resistance somewhere.
(Meter should have shown full battery voltage after all but even the tiny load of a 10,000 ohms per volt (200,000 ohms total ) meter dropped like 2 volts or more) the surprise was finding it "mid run" (well about 2 feet from the battery)

I expected it to be the terminal at the battery.

 

[glenn_c13]

Both of my fans weren't working I installed 1 new fan and it doesn't work although I tested before installation was complete with a battery charger it worked. The one I pulled out and replaced still works. (I wish I would have tested it before I replaced it.) One existing fan didn't work even with the battery charger, my bad I left it running and forgot about it because of the summer heat as the RV sat idle. I checked the interior fuses and did find a fuse blown. I replaced it but nothing yet. Some fuses when I pulled them to check a red light came on till I plugged it back in. What does that mean?
I tested the wires and had 11.04 volts. I've had this problem on my last RV but I can't remember how I fixed it. Memories get foggy at my age.

That 11 volts sounds like the problem with a connection, check negative and positive. It is an easy task to find it. check breakers also. track the 11 volts and you will find it.

 

[pipepro1]

I caved and took it to the dealer. Turns out it was a bad fuse.

 

[Kirk]

Turns out it was a bad fuse.

Did you check the wrong fuse, or ....?

 

[John From Detroit]

11 volts.

Ok two things. Fuses There is an indicating fuse, it has an LED in it and glows when blown
Other thing.. Progressive dynamic fuse panels have an indicator LED. as do some of my other power strips Same idea.. Let you know which fuse is blown

They won't show blown with no load. and well 11.4 volts.. If the batteries are not charging.. About right for what the LED + resistor would drop it.

 

[pipepro1]

Did you check the wrong fuse, or ....?

I replaced a blown fuse but I guess that wasn't the circuit.

 

[Lou Schneider]

That means that it sees an open circuit. It would be the same whether the fuse has been removed or if the fuse is blown, or open.

This is not correct.

Blown fuse indicators typically consist of an LED or warning light connected across the fuse. When the fuse is intact, current flows through the fuse, and the indicator remains off. If the fuse blows or is removed it sees a voltage, causing the indicator to illuminate, signaling a blown fuse. You can easily verify how that works by measuring the voltage across a good fuse and you will read 0 volts, then remove the fuse and measure again and you will read the supply voltage.

Not correct, Kirk. The LED relies on the circuit connected to it to provide a path to ground. It doesn't require much but it does need some continuity. Remove the load wire so the fuse sees a true open circuit and the LED will stay off when the fuse is removed.

 

[John From Detroit]

Not correct, Kirk. The LED relies on the circuit connected to it to provide a path to ground. It doesn't require much but it does need some continuity. Remove the load wire so the fuse sees a true open circuit and the LED will stay off when the fuse is removed.

Correct Lou if the fans are "OFF" the indicator has no return path and won't light.

+----(Fuse & LED)---- / (openswitch)---- Fan--- Ground (neg)
NO light

+----(Blown Fuse & LED)----(Closed-switch)---- Fan--- Ground (neg)

LED glows

 

[CharlesinGA]

If for example, you have a circuit with only a light on it. If you pull the fuse with the light switched on, the blown fuse indicator will illuminate. If you switch the light off (mechanical switch)(fuse still removed) the blown fuse indicator will extinguish because the circuit is completely open.... Downstream of the fuse panel.

If you have an electronic load on a circuit, such as a control board for the fan, or a electronic control board for lights, USB chargers, whatever, the circuit is never open. pull the fuse and the blown fuse indicator illuminates even if nothing is on or running, because the circuit still has loads on it from the electronics of the control boards. (There is a lower limit below which the Blown fuse indicator will go out even with electronic load on it, but it is a few milliamps draw and that is it.)

If you have an older fuse panel that uses the typical ATO/ATC fuses, you can buy a version of the fuse with a built in blown fuse indicator (Littelfuse)(Eaton/Bussmann), but price wise, it might just be worth replacing the 12v fuse panel with a newer one.. If you have a Parallax panel, and you buy a new Progressive Dynamics 4600 series converter for it, it will come with a new fuse panel that has the blown fuse indicators. (replacement fuse panel)