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  #1  
Old September 24th, 2011, 05:40 PM
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Chris Snell
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Tapping accessory power

I need to tap into accessory power and I'd like to do it cleanly. What's the best way to do this? I have a PDF with circuit diagrams for the 97 NAS trucks; I'm not sure if it's the same but it looks like fuse #5 and #6 are hot when the ignition switch is in the first position (radio on, fuel pump and everything else is off).

The problem is, I'm not sure how to tap power at the fuse box. The only way I see to do it is to pull out one of the spade connectors from the back of the box, cut the spade off, add my wire and crimp a new spade with the existing and new wires. This would be fairly clean but I really hate the idea of cutting one of my main harness wires short. Things are already tight:

http://www.flickr.com/photos/defende...in/photostream

Is there someplace else that I could tap into this? I considered tapping at the cigar lighter but this is only hot when the truck is running (second position on ignition switch)...not really what I want.
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  #2  
Old September 24th, 2011, 07:58 PM
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Tom Rowe
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What about a Blue Sea fuse block in the battery compartment? Or mount one next to the fuse box and tap off the battery feed.
Clean and leaves you ready for clean expansion later.
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  #3  
Old September 24th, 2011, 08:06 PM
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Chris Snell
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Tom,

I actually have a Blue Sea box going already. What I'm trying to do is set up a second (smaller) Blue Sea box that is only hot when the accessory circuit is switched on. I picked up a nice 40A relay from a local electronics shop and have it working on my bench. The problem is that I need to tap into a wire that's hot when the accessory circuit is on, in order to trip the relay coil.

I've found one wire, the orange/white wire to the stereo harness, but it would be a hack job to tap into it at the stereo end. I'm searching for another place to tap this circuit. It looks like the passenger compartment fuse box might be a good spot but the only clean way appears to involve cutting the orange/white wire behind the fusebox and patching in another wire and fresh female spade. I just really hate to cut the main harness, especially since it's a very tight space to work in down there.
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  #4  
Old September 24th, 2011, 08:11 PM
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Danny
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Quote:
Originally Posted by chris snell View Post
Tom,

I actually have a Blue Sea box going already. What I'm trying to do is set up a second (smaller) Blue Sea box that is only hot when the accessory circuit is switched on. I picked up a nice 40A relay from a local electronics shop and have it working on my bench. The problem is that I need to tap into a wire that's hot when the accessory circuit is on, in order to trip the relay coil.

I've found one wire, the orange/white wire to the stereo harness, but it would be a hack job to tap into it at the stereo end. I'm searching for another place to tap this circuit. It looks like the passenger compartment fuse box might be a good spot but the only clean way appears to involve cutting the orange/white wire behind the fusebox and patching in another wire and fresh female spade. I just really hate to cut the main harness, especially since it's a very tight space to work in down there.
mine's an imported truck, but I tapped into the rear wiper's switch. Right below the radio and it was easy to cleanly route that to the relay due to already being mostly hidden yet easily accessible.
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  #5  
Old September 24th, 2011, 08:16 PM
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Yeah, unfortunately this truck doesn't have that. I'm not even sure which fuse is the correct one for the accessory-on circuit to the radio. I get continuity between the stereo and and fuse #4 but that is labeled as a heater fan fuse.
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  #6  
Old September 24th, 2011, 08:22 PM
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Danny
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Honestly what I did was (using a test light) focused for easy access circuits that weren't often used. The amount of additional load that the switched feed for a relay is putting on it is so minimal I wasn't worried about blown circuits, more ease of clean installation. I looked at the rear wiper switch (one of the contacts was switched hot), the radio, the wipers in the column, and the actual ignition switch (there isn't a whole lot of electronics in my D90... haha). The radio was already a bit finicky (when I put on the brights it would either hiccup or dim) plus it was slightly harder to access those wires, the column I wanted to avoid entirely if at all possible, and the rear wiper switch was the best choice for me. Try maybe your radio, or figure out (using your test light) which one of the contacts is switched hot on your actual ignition switch would be my advice.
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  #7  
Old September 24th, 2011, 08:55 PM
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Thinking about it, the radio might be an acceptable compromise. I can tap the accessory switched line (orange/white) on the radio harness that connects to the radio itself inside my Tuffy box. It's very close to the battery box and I will only have to run a few feet of wire. It's an aftermarket harness and if I decide to bring the truck back to stock, I can just trash the harness and I'm done. I know that tapping at the fuse box would be the cleanest but I just can't get over cutting on the main harness.
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  #8  
Old September 25th, 2011, 11:13 AM
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Tom Rowe
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If you want clean, then your feed for the relay plugged in to the ignition switch acc terminal using a piggyback connector, and then your normal acc feed plugged in on the piggyback.
Assuming the '94 ignition switch is the same as the '95.
Pull the instrument cluster and you have fairly easy access to it.

If you ever decide to remove it, there would be no evidence it was ever there.
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Four wheel drive allows you to get stuck
in places even more inaccessible.

62 88 Regular
67 109 6cyl NADA x2
74 Lightweight - The Antichrist
95 DI 5-speed
95 D90 5-speed
97 D1 Automatic
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  #9  
Old September 29th, 2011, 06:26 PM
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Tom, that's a great idea. I need to look for an insulated piggyback like that one. For now, I'm just going to tap off of the stereo harness--not the truck's actual harness but the little harness that adapts the Audi/VW-type socket to the Alpine head unit. It's not as fancy but it's easily removable and the total wire run is less than 3'. Using properly colored wire for the job.
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  #10  
Old September 29th, 2011, 06:59 PM
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Keith Imbriglio
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This is what I use http://www.tessco.com/products/displ...59&eventPage=1. Pull out the fuse in the fuse box that does what you want (constant, acc, switched ignition) and you replace it with one of these and you instantly have a wire to tap into. They are available in different amp ratings. No cutting or splicing of factory wires.
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  #11  
Old September 29th, 2011, 07:18 PM
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Quote:
Originally Posted by esprit99 View Post
Interesting, but it's an expensive fuse.
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Tom Rowe
Atlanta, GA

Four wheel drive allows you to get stuck
in places even more inaccessible.

62 88 Regular
67 109 6cyl NADA x2
74 Lightweight - The Antichrist
95 DI 5-speed
95 D90 5-speed
97 D1 Automatic
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  #12  
Old September 29th, 2011, 07:30 PM
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Quote:
Originally Posted by Antichrist View Post
Interesting, but it's an expensive fuse.
They come in a 12 pack for $16 bucks. Thats like $1.40 ea. Not bad IMO & a huge time saver.
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  #13  
Old September 29th, 2011, 11:11 PM
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Tom Rowe
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Quote:
Originally Posted by esprit99 View Post
They come in a 12 pack for $16 bucks. Thats like $1.40 ea. Not bad IMO & a huge time saver.
LOL oh, I misread it. I thought they were $16 each.

------ Follow up post added September 29th, 2011 11:26 PM ------

Quote:
Originally Posted by chris snell View Post
Tom, that's a great idea. I need to look for an insulated piggyback like that one.
They are pretty commonly available, but of course some are better quality that others.
Page 748 of McMaster Carr's catalog if you want a pack of 25.
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Tom Rowe
Atlanta, GA

Four wheel drive allows you to get stuck
in places even more inaccessible.

62 88 Regular
67 109 6cyl NADA x2
74 Lightweight - The Antichrist
95 DI 5-speed
95 D90 5-speed
97 D1 Automatic
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  #14  
Old October 21st, 2011, 01:23 PM
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Paul S.
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I bought the 25amp Tessaco fuse pigtail to run my Exmoor seat heaters and it works great. Super easy.

If anyone would like one or two just shoot me a message. You can just shoot me a PayPal for a couple bucks for postage and I'll mail them out. Don't need the whole pack of 12.

Best,
Paul
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  #15  
Old October 21st, 2011, 01:31 PM
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Charles Galpin
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So what do you do when the fuse blows? Break out a soldering iron and re-wire the pigtail to your spare you keep?
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  #16  
Old October 21st, 2011, 02:10 PM
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Paul S.
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I'm keeping a couple but don't need the whole lot. Besides, I put in another in-line lower fuse that will go before this one does. Plus the heater kit has it's own fuses as well.

Thanks though.
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