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Unread 05-18-2013, 10:52 PM   #1
Virmagicus
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What type of relay?

I want to hook up a 12v fan for my aftermarket amplifier in my Jeep. I want to use the remote wire for the on/off operation. What type/size of relay do i need and how should i hook it up? What size fuse?

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Unread 05-19-2013, 09:32 AM   #2
CJ7-Tim
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A standard square automotive relay will work just fine. You can calculate the voltage draw of your fan, and multiple by 1.5, or probably be OK with a 10-15 amp fuse.
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Unread 05-19-2013, 09:36 AM   #3
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Just a regular 4 or 5 pin relay. 30 amp will be more than enough. Use a computer fan. Not sure but a 5 amp fuse would probably be enough. Should be able to get a fan at Radio Shack or Best Buy.
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Unread 05-19-2013, 11:37 AM   #4
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Most computer fans pull under an amp or two. Remember they are designed to run on extremely low power. They run on very small gauge wire plugged into the motherboards. Simply put they can't handle a strong current. However being 12V, you can plug them directly to your rigs system and they work peachy also and pull what they need. A one amp fuse is usually plenty to isolate it. On stronger case fans, perhaps a 3A fuse.

http://www.newegg.com/Product/Produc...82E16835608034

Relays to trigger it, that's the catch. They pull so little it's almost not worth it, but just enough, plus they add noise to the line, that you do want to isolate them.

I get most of mine from Parts Express. Here's just an example of ones I buy in bulk:

http://www.parts-express.com/pe/show...number=330-079
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If you can't take a nano-second to press shift/period/etc. and make proper sentences and paragraphs, I don't know if I can take a few minutes to respond to your topics... It doesn't have to be perfect by any means, but a little effort goes a long way.
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Unread 05-19-2013, 12:41 PM   #5
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Thanks for the suggestions. Anyone have a diagram to hook it up? I setup my own system with two amps but i have no clue how to hook up this relay. I'm a mechanical person lol.
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Unread 05-19-2013, 01:11 PM   #6
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Not the greatest diagram but it should work.
86-from radio remote.
30-power.
85-ground.
87-to fans power lead.

A 4 pin relay will be the same without the 87A post.
I have not used a fan on an amp in years but when I did I took the bottoms off the amps and mounted them on plywood. Cut a hole on each end of the plywood and used one fan as a pusher and one as a puller. Worked great.
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Unread 05-19-2013, 01:28 PM   #7
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Thanks MyKeyB Here is a link to my amp http://www.crutchfield.com/S-f51jOCq...MRD-M1005.html. Some of the fins on both fans broke off & 1 doesn't work so i took the amp apart. I'm going to cut a hole where the existing fans are and cut out a new hole using my plasma. Where is the best place to tap in for the power? Should i just go directly to the block where it splits for both amps?
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Unread 05-19-2013, 01:53 PM   #8
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From the sticky at the top of the forum. Just replace the light with the fan and the switch itself with the 12V remote wire that goes to the amp. It's that simple. You don't need the huge gauge wire here either used for lighting.

The relay could handle quite a few fans as long as the wiring and fuse is setup to take the load. And ya, you could pull the power for the fans from the amp's power block. There should be enough extra there without a problem.
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Quote:
Originally Posted by SirGCal
If you can't take a nano-second to press shift/period/etc. and make proper sentences and paragraphs, I don't know if I can take a few minutes to respond to your topics... It doesn't have to be perfect by any means, but a little effort goes a long way.
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Unread 05-19-2013, 02:34 PM   #9
MyKeyB
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Yep. When I used fans that's exactly where I got power from. Right off the distribution block. Also a lot of computer fans will have 3 wires. The yellow wire is used for a speed control. You can just not use the yellow wire or you may be able to tap it into the Alpine's speed control. Another thought is you maybe able to find some fans dirt cheap on Craigslist. I know around here people sell old computer parts all the time. Or evilbay. Or my local Best Buy has these in stock with blue LEDs. Fancy! Probably look pretty cool with the blue voltage display on the Alpine if it would shine through.
http://www.bestbuy.com/site/Cooler-M...&skuId=3340397
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Unread 05-19-2013, 07:32 PM   #10
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I was thinking of just using the Alpines speed control but these fans do no even turn on until they are really warmed up. Way too warm IMHO. I just want the amp to run as cool as possible. Thanks Gents!
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Unread 05-19-2013, 08:41 PM   #11
2jhanna
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If you plan on using a low power fan, why even use a relay ? Most circuits under 10 amps don't need a relay.
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Unread 05-19-2013, 10:12 PM   #12
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Quote:
Originally Posted by 2jhanna View Post
If you plan on using a low power fan, why even use a relay ? Most circuits under 10 amps don't need a relay.
Because how he is going to trigger the fans doesn't have 10 amps to supply... He wants the fans to turn on and off with the amps. The only way to do that is with the remote turn-on signal from the head unit, using a relay (without overdrawing your headunit).

Besides, trying to make excuses to not use a $3 part is pretty pathetic in any case. It's always the better move. I would never prefer to skip a relay. They are simple to use, safer to have then not have, allow more control and flexibility of what you can do with what your doing, etc. It amazes me how often this question gets asked...

EVEN IF I was doing some odd sort of < 10A setup to power something in the cab, I'd still use a relay. If you aren't capable of understanding the overly simple design of the electronic switch, or relay, you shouldn't be doing any wiring at all honestly. And that simple device can be used for 1001 different things depending no how it's integrated into the circuit. The most simple of which is to allow safe transmission of current flow to devices with < 1A being used to throw a switch (300-700mA depending on design).

It's simple, 85/86 are your switching circuits... connect them and the relay should trigger. If there is a diode, the hot end should be at the - side of the diode, as in my diagram, and most often, the 86 side. Master power should be first fused properly, then fed in through pin 30, the common power pin. Then you have pin 87A, the off mode hot output, and 87, the on mode hot output. Power from pin 30 will pass to the appropriate pin 87 in the appropriate switch state... It doesn't get more simple then that. And all vasty more safe then flipping a switch (you can't physically flip a switch this fast. Arching and burning can eventually damage, especially with high-current through switches. Relays contain and isolate this function and do it faster then humanly possible.)

Plus again, simply put, his radio likely couldn't handle the load of the fans for very long. The radio's remote turn on output (or power antenna wire if not otherwise equip) is designed as a signal wire, not power source. Plenty to trigger amps to turn on (which inside there is a relay... surprise...) or to trigger other relays. It could do quite a few. In some extreme cases (5+ devices, rare outside of competition rigs) instead we would use it to just trigger one relay that would in-turn do all of the triggering with significantly more load capacity... Still relays always in use everywhere...
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Sir G. Cal - 2k Sahara TJ

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Quote:
Originally Posted by SirGCal
If you can't take a nano-second to press shift/period/etc. and make proper sentences and paragraphs, I don't know if I can take a few minutes to respond to your topics... It doesn't have to be perfect by any means, but a little effort goes a long way.
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