Fan wiring - amp rack

[Tanner]

Anyone here familiar w/ wiring up 12V computer fans for our purposes. There's a +, - , and a yellow wire coming off the fans and not sure what to do here.

Do I just run a wire from the remote lead off the amps into the power source of the fans or what? I'm already running 3 amps off the remote, so is a relay in order?

Any detailed instructions would help greatly!

[spharis]

Ignore the red, it is for the 5V rail. Most are diode protected, so it will only work yellow 12V+, black -. If you are already using that much on your remote lead then you should add a relay swiched by the lead....let me dig up a link.

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Remote Turn On
All amplifiers in the system will need a 12 volt signal that let’s them know when to turn on. Aftermarket head units provide this but it is recommended that you do not connect more than 1-2 components directly to it. This is because a head unit turn on circuit can only supply about 500mA on average. Most electronic components such as amplifiers, active crossovers and equalizers need about 125mA to turn on. As these components age the current draw can be even higher. If this current draw exceeds the rating of the head unit the circuit can burn out completely.

Instead of connecting each component directly you will want to use a relay. The relay will receive the low current signal from the head unit which will trigger the relay. The relay will then connect the 12 volt signal to the amplifiers and other components. This prevents your head unit from trying to deliver too much current which can burn out the turn on circuitry in the head unit. The generally accepted way to connect a SPDT (single pole, double throw) relay is illustrated below.



Terminal 85 is connected to ground and terminal 86 is connected to the remote turn on lead from the head unit. These wires could be reversed since they both connect to the relay coil but for this illustration we’ll connect them this way. Terminal 87 of the relay is connected to the electronic components remote turn on terminal. Terminal 30 of the relay is then connected to 12 volts. Again, these wires could be reversed. When the head unit is turned on the remote lead triggers the relay which connects terminals 30 and 87 together, sending a 12 volt signal to all of the electronic components.

[Tanner]

So if I had my 3 amps, and four fans (2 blowing and 2 sucking) I would connect my 7 remote leads to 87. Correct?

[mneal]

Yup, everything that gets the 12V sense (turn on) voltage is connected to output of the relay.

So if I had my 3 amps, and four fans (2 blowing and 2 sucking) I would connect my 7 remote leads to 87. Correct?

[spharis]

yepper.

[Tanner]

Ok well I see that diagram is a bosch relay. Now how do I go about choosing which size (amps) of relay?

[TigeDuner]

You can probably use the generic square GM type relay found on the rack at Checker or Auto Zone for about $3.00. We used this relay for something similiar on my son's Mitz. and it worked well.

[TigeDuner]

So if I had my 3 amps, and four fans (2 blowing and 2 sucking) I would connect my 7 remote leads to 87. Correct?

Where are you blowing and sucking the air to and from?

[spharis]

Amps are extremely low. a standard auto relay will be fine. Go to auto zone and buy one off the shelf.

[Tanner]

I tapped into the fresh air vent that comes off the dash behind the glove box. and I'm blowing the air into crawl space down the port side.

[Tanner]

Spharis,

You listed a SPDT relay.... but wouldn't I want a DPST relay? Dual poles... one for the fans and one for the amps, and a single throw (normally off w/ a single throw to the on position)? Or am I lost?

[spharis]

It depends on how you want the fans to turn on; turning everything on at once, vs independant control. There are several options depending on what you choose.

[Tanner]

I'm wanting them to come on at the same time as the amps, and be on whenever the amps are on.

[zad0030]

I read this thread and didn't comprehend anything. We wanted the fan to turn on at the same time as the amp as well. We were told to connect on of the three wires on the fan to the REM, and another to the ground. Later we found out that we cannot do that with the model amp we have or something... So we ended up have in tied in with the key so whenever the key is on or on ACC the fan comes on whether the stereo is or not.

[TigeDuner]

That would be a safe way to ensure the fans are on. You could also attach them to the yellow antenna up wire if you have one.