External cooling fan for MFDs

[crck0848]

My helm has three TZT16F MFDs. I'd like to add an external exhaust fan that turns on automatically when I turn on the MFDs. Can anybody suggest a way to do it? Is there a wire on the Multi Cable that could be repurposed to turn on a fan relay?

I want the MFDs to run cooler, but I don't want a fan running 24x7. I could install a fan switch, but automatic would be better.

Thanks.

 

[Johnny Electron]

If you don't plan to use an external buzzer, you could likely use the +12v (Pin4) normally used for the buzzer and the ground (pin11) to trigger a small relay to turn on fans whenever the unit is ON. The 12v on Pin 4 is there whenever the machine is turned ON. The buzzer is switch on and off by the ground being applied on pin 3; not by the power. Power is always there. You would want a relay that can switch at 100ma or less.

 

[crck0848]

Perfect! Thanks Johnny!

 

[crck0848]

In case anybody else wants to try it, this relay works as expected:

https://www.amazon.com/dp/B095YFJ69T

Here's how to connect the input side of the relay.
MFD "12V_OUT+" (red wire) to relay "DC+" and "IN"
MFD "GND" (black wire) to relay "DC-"

When I turn on the MFD, the relay closes and turns on the fan.

 

[Johnny Electron]

Thanks for sharing!