need help replacing fans

[neoreef]

I don't know electricity at all. I ordered some replacement fans for my JBJ PC light hood, because the fans that are on there are noisy and sometimes don't work. I got some that have 3 wires coming off of them. At the place I bought the fans, they sold 3 wire to two wire adapters so I bought some of them.
I connected everything up in a logical sort of way, and everything fit properly, but the fans would not start up....so I put the old fans back in and reinstalled the fixture so my corals won't die.
WHY didn't it work? what was the third wire for? I bought these fans because they were advertised as quieter, while being the same size and voltage.
Can anyone help?

 

[tony detroit]

The third wire is most likely a ground, the lower pin type plug on a standard wall outlet I would guess. Why not just wire it directly to a 3 pole plug instead of using the adapter, this way you are grounded properly. Put up some pics if you can.

 

[reefraff]

You need to figure out if the new fans are the same voltage as the old. If one of the wires is green it could be a ground. My fans have three wires but the third is for a thermistor which contols the fan speed based on the air tempature.

 

[neoreef]

The fans are the same voltage as the old. They are 12 v DC fans
the third wire is yellow. There was a description of the fan that said something about speed control, and I'm sure my old fans didn't have that, but I thought if I used these adapters, I could ignore the speed control functionality. When I had them hooked up to my lights, I tried heating the fans with a hair dryer in case they were too cool to turn on, but they still didn't work.
Perhaps the speed control is connected to the third wire, but i am lacking the thermostat or whatever it takes to get them to use that third wire.
I don't think it is a grounding wire. The plugs are not like the plugs that you put into a wall outlet. They plug into a tiny wired socket deep in the tunnell that is along the edge of the inside of the light fixture. It appears that all the electrical fittings are in there, but it is impossible to get my fingers in more than an inch or two. To plug in these things, I use a flashlight and a hemostat to grasp the tiny plug firmly and stick it in the tunnel and up into the socket.
If it were a grounding wire, the fans would work without it.
Thanks for your help, and if anyone has another idea, I would be most gratefull.
Kathy

 

[neoreef]

Originally posted by chriscobb
Why not just buy 12v fans and put cords on them and wire them into a switch that controls you lights???? You want your fans on when the lights are on. That would be awhole lot easier
Chriscobb,
Thanks for your interest. I bought 12v fans. They come with wires. I can wire them to the switch that controls my lights. What I cannot do is MAKE THEM WORK!!!!!!!!!!
My old fans come on when the lights are on. It is easy. It is also very loud, and the fans don't reliably spin, or spin slowly at times. I want to swap them out for new fans, but the fans I bought, although I can plug them into my light fixture, DO NOT WORK.
This post is asking if anyone knows why they fail to fan, and if there is something I can do to get them to work.
Does anyone have experience replacing the fans on a JBJ PC light fixure? Any computer electronics buffs out there?

 

[spline9]

I dont really have a solution but just to comment on the yellow wire. Most likely its just an RPM sensor. It probably just reports to the controlling unit how fast its going. Dont bother connecting it if you dont have anything for it to connect to. The fan should just run with the other two wires (probably red and black) connected. One wire for power, the other for ground. Thats all you need.
...at least this is what goes for PC fans.

 

[neoreef]

yes, that's what I thought should happen, but the fans don't work. I have a querie in to the company that sold them to me. Perhaps they will know why they don't work....
Thanks for your thoughts.

 

[dskidmore]

Try switching the black and red. I agree the yellow is a signal wire and should not be connected.

 

[reefraff]

Assume you have a black, red and yellow wire coming from the fans. Your fixture hopefully has a black and red wire. If that is the case just wire black to black and red to red and you should be ready to go. My fans run no matter how cool things are, they just speed up as the temp increases. The tempature sensor on my fans looks like a small metal bulb at the end of a wire so I assume it is a small thermocouple. If that is what the end of your yellow wire looks like just leave it hanging where you want it to sense the temp.

 

[neoreef]

Thanks to everyone. I am a bit frustrated. I won't get the info from the company until tonight if at all.
The fans are pre wired to a tiny plug. I guess I should post a picture. If I don't get a solution from the company tonight, I'll take pix and post them.
Sorry if I have been a little gruff. I do appreciate your interest and attempts to help.
Kathy

 

[neoreef]

This from the company:
It should work fine if it's DC 12V and your connector is right type.
The third yellow wire is speed monitoring wire(monitoring RPM).
These fans have virtually no defective rate.

 

[neoreef]

no...:nope:
I'm sure it was connected properly the first time I tried, and I haven't had a chance to try again. I'll keep you posted. Thanks for your interest.
Kathy

 

[neoreef]

Originally posted by neoreef
This from the company:
These fans have virtually no defective rate.
Correct! The adapters, however were wired backwards. Here's how I figured it out:
I plugged in the new fan and turned it on: nothing
I unplugged the new fan from the adapter and tried the old fan in the adapter: nothing.
then I compared the adapter plug with the old fan plug, and, yes!, black was where red should be, and red was where black should be!
I switched the wires, plugged it back in, and heavens to Murgatroid, it worked!
Now my problem is that the screw holes in the new fans are not countersunk, as they were with my old fans. The screws are not long enough to anchor my new fans in my old hood, even though the fans are exactly the same size, so off to the the hardware store I go.

Thanks for all your input,
Kathy

 

[spline9]

Hehe and I was thinking to suggest possible reversed wires. I think I was just figuring that the fans would just spin reversed. *shrug*
Glad you got them working!