12v Fans bogging down?

[Nicholson58]

Originally Posted by wingssail

These Hella Turbos are quiet and use little power and they are the "standard" fan on Wings. We have 7 installed and about 4 of those are operating at most times in the tropics. You cannot get more than 48 inches from a Hella fan in our boat. We have used Hella fans for about 25 years. When I go on other boats as navigator I take my own Hella and alligator clips. The ones we have now are at least 5 years old and running fine.

The key is to keep the bearings lubricated with very light oil, WD40 works well, and keep the oil off of the circuit board. The resistors are delicate and overheat easily, and then are soon fried. Even a little heavy oil, like 3in1, can put a drag on the bearings and cause overheating. Cleaning the speed control sliders is also useful, use alcohol. Taking the fans apart to clean and lube them is just a little tricky, but once you learn how to do it, it is quick and easy.

Computer fans are also good, but the installation is not as elegant.

WD40 is not lubricating oil. It is sticky goo in a solvent. It is designed to make a tenacious moisture resistant coating to protect against corrosion or to act as a penetrant. When the solvent leaves, the goo remains. Spray some on a smooth shiny surface and check on it in a few weeks. A wax like coating remains. It is no wonder you need to take apart and clean. I suggest a very light mineral oil. If there is room to add a felt pad on the shaft you can saturate it with the oil to act as a reservoir and extend service intervals.

[Sternwake]

Originally Posted by Jim Cate

I've been using 3 dollar PWM "dimmers" from the internet to control speed on muffin fans. Works quite well for little money or time spent.

Jim

I've removed all my 3$ PWM led dimmers, as they make many of my LEDs whine at reduced brightness, fans also whine at reduced speeds, and the leds begin to flicker after a couple hundred hours.

I do have a 21kHZ pwm motor speed controller that does not make the whine audible to my ears. I think I saw one of the dimmers advertise 13khz

The 5 for 12$ voltage buckers I use as speed control/led dimmer are 150kHZ.

no flickering, no whine, and the leds can be dimmed all the way. The issue is replacing the tiny blue voltage trimpot with wires to a remote potentiometer

[SKMT]

Originally Posted by wingssail

Even a little heavy oil, like 3in1, can put a drag on the bearings and cause overheating.

Interesting...because 1 fan was rattling a bit recently so i first tried a little teflon lube. After that didnt work, i used 3-in-1.

[SKMT]

So assuming my issue is the 3-in-1 I recently used to lube the fans, is there any way I can get that oil out of there? If not, is there something i can try spraying in to thin the 3-in-1?

[Nicholson58]

Originally Posted by SKMT

So assuming my issue is the 3-in-1 I recently used to lube the fans, is there any way I can get that oil out of there? If not, is there something i can try spraying in to thin the 3-in-1?

We have 24 volt DC computer fans on our Frigaboat air cooled units. One gets airborne contamination on the shaft and bogs down. I found the peel and stick label gives access to the fan shaft retention. Once removed, I clean with acetone including a pipe cleaner through the bearing bore. Tiny touch of sewing machine oil and reassemble and it runs for months. I found that trick grease and Teflon was not as good and shortened the time between cleanings.

I suggest disassembly and total cleaning of running bits with solvent. Use light oil very sparingly on reassembly.

[jamhass]

I use 12v computer fans mounted in a simple teak frame. Fans are brushless with bearings and last several years in a marine environment, a bit longer if the electronic board is sprayed with a protectant such as Bohield. Cheap and easy to replace when they die. I make them 2 speed with a simple resistor across the single pole duel throw switch I use mounted in the frame.

I have noticed that they can slow down when the blades get dirty.

[BlackHeron]

If you buy them from WestMarine you can get the extended warranty replacement plan with purchase which is good for 5 years I believe.

If you cruise full-time the fans will not last that long running nearly constantly. The extended warranty is well worth it. We use Caframo 747 guardless fans as they are quiet and efficient without the guards in the way -but they do wear out in a few years. We have a few fans that almost never get shut off in the warmer seasons. These little plastic fantastic 12v fans are just not up to continuous use and were not designed to have parts like bearings/bushings and brushes replaced. Just trying to disassemble them is an exercise in futility. They are cheap disposables and for the vast majority of boat owners that is more than good enough. Those of us who cruise full-time will see them wear out every couple/three years.

[Sternwake]

One of my favorite 12v computer fans, used as an intake fan, failed yesterday. I found it varying speed wildly and not responding to the potentiometer as it should.

Its voltage bucker/speed was outputting rock steady voltage.

This particular fan, simply lifting up the sticker on the hub, to access the wire entry solder joints was not possible, the impeller has to come off, which is why i did not do my usual covering of this area. Locate foot, aim, shoot.
All it requires is some snap ring pliers, but I've lost that snap ring in the past when it flew away and disappeared, thus my hesitancy to do it.

When I did remove the impeller, no surprise I found dust and white and green corrosion bridging the + and - at this point, and nearby the green was lifting off the circuit board. Almost EVERY computer fan failure I've had, has these same symptoms.

It worked fine for several minutes after cleaning off the dust and corrosion, with no issues, but after a period of rest, later failed to fire up at all and had that burnt electronics smell, much to my disappointment.

I moved its bucker to another 12v 120mm fan, a very inexpensive yet powerful one which was poorly balanced and vibrated badly at half speed or higher. Using an accellerometer app on my phone I was able to balance it to pretty good levels. Not perfect by any means, but it only becomes bad at near max rpm, and that amount of airflow noise and amp draw, is rarely required/desired.

This cheaper fan has what appears to be a conformal coating over the circuit board's components, like a clear nail polish/varnish. I'll be getting some clear nail polish to protect existing and future fan's circuit boards.
I've already ordered a replacement of the one which failed yesterday. Should be here by Friday for under 12$.