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Unread 05-30-2013, 08:31 PM   #1
atomicjoe23
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Underdash switched power source???

This is probably a pretty basic question, but electrical is not my forte. . .

. . .what is a good source for switched power under the dash?

Since our stock radiator leaked I'm taking the opportunity to upgrade to a an aluminum radiator and electrical fan. I've got it pretty much all finished except for a few final wiring connections. . .one of which is a switched power supply for my manual over-ride switch in the dash panel.

I'm also gonna be hooking up some PIAA lights while I'm at it. . .I figured a good way to run power to the lighting relay would be with the headlight power so I can only turn the lights on if the headlights are also turned on. . .I figured that would be a good way to keep from accidentally turning them on during the day or accidentally leaving them on. Is this a good idea or is there a better source to power the relay from?

Thanks for the help!

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Unread 05-30-2013, 08:50 PM   #2
Old4X
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Get a test light and find an ignition switched fuse on the fuse panel.

Get an "add a circuit" from the parts store (5 bucks) and use that as your source. No cutting or splicing needed.
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Unread 05-30-2013, 08:56 PM   #3
Anticanman
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I believe you should cut into the harness for the radio and run it to a toggle switch before it goes into a relay. That way you can turn it off for water crossings. Don't forget the two speed controller.
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Unread 05-30-2013, 11:50 PM   #4
atomicjoe23
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Thanks Anticanman. . .yep, the power is going to a switch to be able to turn the fan off for water crossings; as far as the dual speed goes I'm only running one temp. sender, so high speed will be controlled by a 3-way switch and be a manual over-ride speed.
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'94 Jeep YJ Wrangler
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'49 Jeep Willy's Truck
350SBC/TH350/NP205, 14-bolt rear/D60 front
40" BFG MTR's on H2 8-lugs
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Unread 05-31-2013, 04:06 AM   #5
jsawduste
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Quote:
Originally Posted by atomicjoe23 View Post

. . .what is a good source for switched power under the dash?

Since our stock radiator leaked I'm taking the opportunity to upgrade to a an aluminum radiator and electrical fan. I've got it pretty much all finished except for a few final wiring connections. . .one of which is a switched power supply for my manual over-ride switch in the dash panel.
Switched power can be had from the fuse box. A "piggyback fuse" will suffice if need be. Another is the blue with a white tracer wire. You NEVER want to cut into a harness. Most folks don`t have the proper connectors or talent to do so. Much better to add a circuit from the fuse box which can be done very simply with a piggy back fuse. That is the root of electrical gremlins and said action is often a topic here.

The PO cut into the harness and now it.........

The aluminum radiator unless one of the models from CBR or Ron Davis is not an upgrade and an electric fan is never an upgrade. An all brass from a reputable company (I use Hesco) is the better choice. Hesco can sell you a 3 row if you think you need it but you really don`t. If you don`t believe then think of galvanic corrosion if nothing else. Two widely dissimilar metals and without proper grounding the corrosion is simply exacerbated. Contrary to the belive aluminum is not all that much better conductor of heat. But it is shiny and can sometimes be lighter.

Many others in the industry do not like electric fans, myself included.Too many things to go wrong and the fallacy of increased performance is just that, a fallacy. The amp draw loads the alternator as much or more the the mechanical fan.

Yes I have run electric fans and the best mod I`ve done was to toss the fan and add a factory shroud and clutch fan with the Hesco radiator. The engine runs cooler (in fact I`d like to see a little higher temp) and the coolant temp stays much more stable then it ever did with an electric. Allowing the ECM to tune itself optimally rather the compensating for a variance in temp.

75% of JFers will disagree but it works is reliable and maintenance free. If you pay the shipping I`ll give you an electric fan.
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Unread 05-31-2013, 10:37 AM   #6
Firefyter-Emt
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I would have to look at my 1995, but on my 1991, there were some spade plug type ports in the fuse box that would allow you to plug in a spade style plug directly. I will take a photo at lunch if my 95 has the same set up. Idealy, install a small aux fuse box, with a 30amp fuse from the battery, but switch the fuse box with a relay off one of these fuse box ports. (or a piggy back clip)

I found this on-line, but it's done exactly as I recomend. Once done, you have a fuse box that can draw off 6 fused outputs for a max of 30 amps (or higher if you wire and fuse accordingly)



Saved some time and did a quick Google... Note the single sockets that you can use... Use one of those to switch the relay. You can power directly off that, but adding a fuse box properly, will wire for the future!

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Unread 05-31-2013, 10:46 AM   #7
jbolty
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I added a blue sea auxilary fuse box and powered it directly off the battery using a 75 amp continuous duty relay. All my added electrical items are turned off and on with that plus each having their own switch.

Not the best picture, but there it is.

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Unread 05-31-2013, 01:21 PM   #8
jsawduste
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Great descriptions and pictures guys. Hopefully the OP and others will follow your lead and NOT hack into the harness.
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Unread 05-31-2013, 03:17 PM   #9
Anticanman
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What's wrong with tapping into the back of the radio to utilize milliamps to initialize a relay? Anyone who has installed an aftermarket stereo knows which one it is and its readily available and usually already spliced to another wire to an aftermarket head unit harness.

Am I missing something here?
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Unread 05-31-2013, 05:28 PM   #10
Firefyter-Emt
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One could tap the harness, but when the fuse box has easy to use plug and play ports, why tap a harness? Over time, harness that have been "tapped" tend to corrode inside the wire and can lead to problems down the road. (trust me, a "poke" from a test light alone at the coil harness took my Jeep down all last summer!)

I agree with using the relay to switch a heavy gauge fused wire. Just do it from that fuse box shown above, and run it to a cheap fuse box found at any auto part store. Problem solved, and problems down the road solved too!

Just for kicks, and because I am a nice guy... This is a photo of the box out of my 95. (Gotta love the AMC logo still on the top of the box, huh)


image-3663088780.jpg

*The three along the left side are all 12v switched in run/accessory.
*The one to the right of the 15amp fuse labeled "ACC" did have 12v in run/accessory, but seemed to turn off after a couple minutes with the key on....
*The one listed as "Clock" is 12v battery and is not switched, but solid 12v.
*The one to the right of the 15amp fuse listed "ING/LPS" s kind of cool, it has 12V switched, but in run only. This would be very sweet to use for the power side of a relay for driving lights. You could toggle switch the ground side of the relay switch and your driving lights would never turn on if the key was in the Accessory position, and turn off with the key.

All of these ports will take a standard male spade terminal, or better yet scrounge the junk yard for that old style radio plug shown in my first photo. I had my radio power wires hooked to two ports for about 10 years and never had a problem with the wire falling out. Just keep in mind, these are not fused ports!
image-1672323854.jpg  
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Unread 05-31-2013, 10:01 PM   #11
atomicjoe23
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WOW, these are probably the most helpful responses I have ever gotten back. . .thanks for all the help!

I didn't want to tap into the harness if possible, but I wasn't sure how not to. . .I had never even considered checking the openings in the existing fuse box, and I had always wondered what those single slots were for. . .very helpful now on this project, and in the future on this and other projects as well.

You guys hit it out of the park on this one!
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'94 Jeep YJ Wrangler
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'49 Jeep Willy's Truck
350SBC/TH350/NP205, 14-bolt rear/D60 front
40" BFG MTR's on H2 8-lugs
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