Automatic AC Fan Switch Mod

ahbradford

Hi all!

I have a quick DIY fun mod I cooked up that makes it so the AC ventilation fans will automatically be enabled when the AC is turned on, and disabled when they are turned off. Total cost is around $40.

It requires the following parts:

Automatic Power Tool Vacuum Switch
Relay Switch
USB power brick (an old iPhone power adapter works great)
USB cable
Multimeter
Misc wiring

Ok, here’s what you do.

Take the AC plug and move it into the Vacuum Switch A, and plug the vacuum switch in where the AC plug was previously.

Then take your USB brick and plug it into the vacuum switch that would normally control the vacuum.

Now, you need to take the usb cable and cut it, and splice into the 5v power lines, verifying with the multimeter. You only need the 5 V lines. The data lines are unused (obviously).

Ok, now wire up your 5V lines to the relay. You want to set it up to close the circuit when 5V is applied.

Now, just go behind the dash where the AC fan switch is, and run a parallel line through the relay’s output.

That’s it. You can always turn on the fans manually, and they will also kick on when the AC draws more than 30W or so. Best of both worlds.

So, the flow is: The AC turns on, the vacuum switch detects the current and turns on the outlet, which is hooked to a USB brick, that has it’s 5V lines attached to the relay, which closes the fan circuit.

Now, you’ll never have to remember to flip that switch ever again.

Here's a link to the parts I used.
https://www.amazon.com/gp/product/B07YK9VBQK/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
https://www.amazon.com/gp/product/B00LW15A4W/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

And a couple of photos.

Let me know if you have any questions, good luck!

HikinMike

Very nice