What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Avionics Cooling Fans

Geico266

Well Known Member
Do NOT reverse the polarity on these little fans. Bad things happen so it won't work. I'm sure Stein can give us the technical reason why..... ;)

Years ago I used to be able to switch polarity and they would run backwards. No longer the case with these cooling fans.

If you have tested them (Red = Positive, Black = Negative) and they don't run you'll need to buy new ones. $6.00 each

I'm heading back to the shop to see what else I can break. It's one of those days.
 
Last edited:
well at least they're only $6. Same fan is $20 at Radio Shack.

Live & learn.

What was funny is the avionics tech at Van's thought you could reverse them also. He had no idea they would burn up. He said a guy building the -12 called and said both fans were defective. My guess is someone else out there is doing some unauthorized testing also! :D
 
I also found out the hard way about NOT reversing the polarity on the cooling fans. If you look at fig. 1, page 31-04, you see that both fans are wired red, positive, black negative- with both fans in the upright position. If you duplicate this setup, both fans will blow upwards, and yet, the fan on the right is supposed to blow downwards. I called VANS about this and asked Joe if I should reverse the polarity on the right fan or just turn it upside down. He replied that either method was OK. When I tested the right fan with polarity reversed on my 12 volt test cell, it fried! I boxed it up and sent it back to VANS, with a note saying I wanted a replacement. It will be interesting to see how they handle this. By the way, I have since found out that they are brushless motors and cannot be reversed with reverse polarity because their electronics won't handle it. I do think that the guys on VANS help line should be aware of this sort of thing, and if they really don't know the answer, should refer you to someone who might. Steve
 
I also found out the hard way about NOT reversing the polarity on the cooling fans. If you look at fig. 1, page 31-04, you see that both fans are wired red, positive, black negative- with both fans in the upright position. If you duplicate this setup, both fans will blow upwards, and yet, the fan on the right is supposed to blow downwards. I called VANS about this and asked Joe if I should reverse the polarity on the right fan or just turn it upside down. He replied that either method was OK. When I tested the right fan with polarity reversed on my 12 volt test cell, it fried! I boxed it up and sent it back to VANS, with a note saying I wanted a replacement. It will be interesting to see how they handle this. By the way, I have since found out that they are brushless motors and cannot be reversed with reverse polarity because their electronics won't handle it. I do think that the guys on VANS help line should be aware of this sort of thing, and if they really don't know the answer, should refer you to someone who might. Steve

The fans have an arrow showing which way they blow. You can mount them with either side down so you can have one up and one down.
 
I didnt burn one up but i did have one defective one and they replaced it no problem without even asking for the other one back. This was weeks ago. They do say, "made in China" on them, probably some toy factory.
 
The fans have an arrow showing which way they blow. You can mount them with either side down so you can have one up and one down.

Agreed Jim, but the drawing shows them both pointing in one direction which indicated to me that I could reverse the polarity and get one to blow down. This is how I burned one up. :mad:

Live & learn.
 
thanks Jon...I know they worked at one time. I tested both fans at 12V and they work. BUT Power at the wire to the fans (with Master on) from the AV5000A (Control Module) block is only 0.03V. not enough to power run the fans. Is this circuit on a temp sensor? Everything else seems to be working.
 
Back
Top