12v fan

[Chip]

ok folks I got an electrical gremlin in my cabin fan,,, it one of the 12 volt, battery units from Wal Mart,, you know the ones that are battery powered or 12 V ac adaptor,,,,here is my situation,,, I cut the battery pack and battery tabs off, I mounted the fan in the footwell and hard wired it in to my 12V system,,,, it works great ,,,, for about 15 minutes, then it all of a sudden, slows to a little less than half speed on high,,, low speed is slightely reduced also,,, power convertor is cool as are all the wires,,, after something cools down it works great again,,,, all the lights on the same circuit work fine,,, might just be a bad fan but would like any ideas yall might have,,, here is what it looks like installed




I appreciate any insight yall might have,,,


chipper

[Juneaudave]

The traditional "ground" perhaps?

[SteveH]

Chip,

The way to find out for sure is put a volt meter on the wiring at the point where it goes into the fan motor, and monitor the voltage when the fan slows down. If the voltage does not drop, the problem is the fan motor....if it does drop, it's the wiring, and I would look for a bad joint. Good luck.

[kirtsjc]

Looks like an awful tiny motor to run that fan... looks from the motor housing that it has one of those real cheapy DC motors that overheats easily.

By all means do the voltage check thinggy that SteveH suggests, but I suspect you might have to replace the entire assembly...


My *theory* is that you may not have enough vents open in the tear for the fan motor to cool itself, and you get the overheating shutdown. I see that your exit ventilation is VERY ample...

[madjack]

Chip, Steve's advice is very good...if not a bad motor, a bad joint can heat up as current passes thru it and cause it to open even further resulting in a vicious circle.......
madjack

[Chris C]

Chip,

Hate to ask this now, but did you try it out sufficiently before cutting it all apart to mount it in your trailer? Ya know they aren't going to take it back now. Dang, I hate that.

[Finntec]

Just a thought. Could you be creating a negative pressure on the other side, which slows down the ability of the fan to pull air through the wall?

[Chip]

Thanks folks for the thoughts and advise,,, One thing I dont think is a problem is restricted air flow,,, the second pic is the intake in the galley,,, the area is almost double the area of the fan plus I had the a/c plug hole open also,,, and on the exhaust side ( fan pulls air from galley and blows on my feet) the door was open and a window,,, dont even say I got big feet and blocking air flow,,, just ask my girlfriend or one of my ex's,, they will testify to dat

guess I got to put a meter on the wires and see what happens,,, also gonna check my connections,, an electrician I aint,,,

Chris,, I tested it for just a minute,, but this dang gremlin dont show up until the fan runs for about 10 to 15 minutes,,

heck yea its a cheepy fan,, its only 13 bucks in the fan section and 14 in the camping section with 12/120 convertor,,, so no great loss if its a bad motor,,,

thanks again guys for the input,,, see some of you this coming weekend

chipper

[JasonTX]

The problem could be that it's simply a walmart product. I have had some very bad luck with walmart items. I nearly burned my house down from a ceiling fan I bought there. Totally off topic here, but I once bought a gas grill there and the box said "No tools required for assembly." Long story short, it took every freakin tool I had to put the thing together.

[Miriam C.]

Chip
It sounds like the fan is building some resistance. Anyone know if these fans have a built in resistor that will cause the fan to slow or cycle?

BTW- What size wire do you have?
Aunti M

[mwolford]

Hey Chip,
Is there any way to get at the motor bushings? You might try a drop of oil (NOT WD-40) on each end of the motor shaft to see if that helps.

Good Luck!
Mike

[GeorgeTelford]

Hi

Just a few thoughts

Bushes, hmm if the bushes were getting tight from heat this problem would not cycle (bushes would stay semi seized until unit switched off for a while, either that or they would fully seize)

Build up of resistance, again why with continued running would this suddenly reverse? Only thing close to this was a dry solder joint on the motor powerfeed

Can you try it with a direct power source Mains or direct battery? to eliminate the wiring run?

[Chip]

Ok ,, so far I checked the wiring connections,,, they are good,,,, the case is plastic on the motor and after running a few minutes I did notice a spark inside the case while running,,, this tends to make me believe the motor is a "dud" now I havent checked further with a meter but I did put a drop of oil on the rear bearing,,, test to follow,,, I have just been busy trying to pack for the N/S get together ,, If push comes to shove Ill leave it off and resort to a 110V fan or the A/C,,, but I aint finished with this dang thing yet,,,, ,,,, George when it did slow rpm's it only speeds back up after a rest,,, ??? Might just have not gotten my kiss from the good ladies from Japan that put this thing together,,,,,

updates to follow

thanks guys,,

chipper

[Miriam C.]

Chip,
This fan doesn't happen to have a battery saver feature that keeps it from running full out all the time does it?

If it just cycles low and then goes back high on a regular bases it may be intended to do just that.

Miriam

[Chris C]

Chip,

I've got the same fan.......................sure hope I don't have problems with it. I only turned it on long enough to decide it put out plenty of air in relation to the amount of noise it made.