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First off... I would like to say thank you all for the wealth of information about our vehicles on this site. :ro)

Yeah, I've been lurking and reading for the past couple months :eek:: since I bought my truck. I bought my truck to pull my toy that you see in my sig.

I just completed a gauge install and wish to share a little information on the install.

A common question is where to find power for the lights on the gauges. Some people choose to just find hot keyed power for an always on situation. Others hope to get the gauges to work with the instrument panel (and better yet the dimmer switch function). For this, the consensus seems to be to splice into the appropriate wire behind the headlight switch in the dash. There were many posts on this. There is an alternative... and I only saw something about this mentioned by one other person... sorry I can't remember your name... but I checked it out. Now I want to share with anyone else getting ready to install gauges.

To get "dimmer functioning power tied to your headlight switch" for your gauges... simply open the black box by your left foot (by the emergency break pedal). In here are a few relays of various sorts. You'll notice a bunch of empty pins where nothing is attatched. Take your test light and go hunting. I found mine in 2 minutes on the bottom right corner of this black box where there is a bank of 6 unused pins. I then simply used a mini blade connector (female end) like you would install over a fuse tap and put it on the pin. Worked like a champ! It is possible that not all vehicles have the exact same configuration, but I'm guessing you'll find a suitable power source there regardless. :)
 

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First off... I would like to say thank you all for the wealth of information about our vehicles on this site. :ro)

Yeah, I've been lurking and reading for the past couple months :eek:: since I bought my truck. I bought my truck to pull my toy that you see in my sig.

I just completed a gauge install and wish to share a little information on the install.

A common question is where to find power for the lights on the gauges. Some people choose to just find hot keyed power for an always on situation. Others hope to get the gauges to work with the instrument panel (and better yet the dimmer switch function). For this, the consensus seems to be to splice into the appropriate wire behind the headlight switch in the dash. There were many posts on this. There is an alternative... and I only saw something about this mentioned by one other person... sorry I can't remember your name... but I checked it out. Now I want to share with anyone else getting ready to install gauges.

To get "dimmer functioning power tied to your headlight switch" for your gauges... simply open the black box by your left foot (by the emergency break pedal). In here are a few relays of various sorts. You'll notice a bunch of empty pins where nothing is attatched. Take your test light and go hunting. I found mine in 2 minutes on the bottom right corner of this black box where there is a bank of 6 unused pins. I then simply used a mini blade connector (female end) like you would install over a fuse tap and put it on the pin. Worked like a champ! It is possible that not all vehicles have the exact same configuration, but I'm guessing you'll find a suitable power source there regardless. :)
Yeah, I mentioned it several times. No one seemed to like the idea, always wanted to spice into the brown/white wire. Glad someone found it useful. Be a little careful down there, there is also connections for the led dimming. You can get more wiring info on gmupfitters.com.

Jim
 

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Yep P 263 through 266 shows a few points, makes no sense to me why people will splice the center of a wire when there are plenty of good places to get at it.
 

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I went to that web site and all I found was them wanting to sell a wiring diagram.
No way would I rarther splice a wire than connect to a exhisting pin connection.
How can I tell whether its dash dimming or led dimming so as to make the correct pin location?
Thanks, Merle
 

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Just exactly which pin is it? I was hunting this pin when I blew out my dimmer switch. :Nonono: Don't want to do that again. Can anyone guide me a little closer to where I need to tie in on an '02 lb7? Also, where is a good place to tie the boost gauge hot wire into ignition?

Any help greatly appreciated.
 

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will this work on an 05?
Yes I have done it. In the relay panal down at the floor board there is some open spaced for extra relays. Why I don't know. But I used a test light and found the open relay in the top right corner is the one I used. I found a open post that was on the same circut as the dimmer switch so I wired a female wire pin on pluged both guage lights into there then in the same open relay I found that was an ignition on only pin, there went the pryo probe hot wire. The grounds all went to the metal box by the parking break release handle. My only suggustion is to put in some in line fuses. I first wireing into the relay box on my '98 model work truck that I put in a take out electric seat. When my local auto parts store didn't have tap fuses I went back to the relay box for the gauges. Get you test light and start poking around in it, thats all I did.
 

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Here's what Wayne has linked in his reply - I've copied it over to this post. I'm going to start working through this soon & will post results.

From Wayne:
Unless you have some unusual factory options there are 3 unused circuits you can tap into inside the cab. They are available in the Relay Block I/P, also called the Mid Bussed Electrical Center (MBEC). This is the junction box under the dashboard to the left of the steering column that a trailer brake controller also plugs into.

After you remove the cover, locate connector C8, which is the upper-left position. There shouldn't be a plug in it. Pin D, the upper right pin, is hot in ACCY and RUN. It's fed through the SEO ACCY fuse, 10A, in the Left I/P fuse block. Pin A, lower left, is always hot. It's fed through the SEO B2 fuse, 30A, in the underhood fuse block. Pin E, middle right, is always hot. It is fed through the SEO B1 fuse, 15A, in the underhood fuse block, Pin F, lower right, is a ground. As far as I know, these are totally unused circuits. Why GM ships the trucks with the fuses inserted is beyond me when they're removing other features that most people care about. The other available pin in connector C8 is pin C, the upper left pin. It is hot in START and RUN, and fed by the 10A SEO IGN fuse in the underhood fuse block. This circuit also supplies power to the rear window defogger relay coil (not the defogger itself). I don't know anything about pin B. It's possibly not used.

You can use various modified connectors to hook onto these pins. The correct connector is a black 6-way Metri-Pack 280 series unsealed connector. They do not seem to be easily available. I saw a post mentioning that they were over $40 from the dealer but I haven't checked that out myself. The only other source I found was a distributor that sells them in quantities of 2,000. If you don't mind a little surgery for a compromise solution, you can pick up a brake controller harness at an RV store for about $15. If you get the one that plugs into a Prodigy brake controller (the most common harness version), the 4-way connector that you cut off and don't use contains 4 female spring connectors that fit pretty well on the Metri-Pack 280-series male pins.

The trailer connector is meant to go into position C7 of the MBEC, just to the right of the C8 connector I'm talking about. At first glance, it looks like you can just cut one keyway in the trailer connector and it will fit into C8, but it's not than simple. If you look closely you'll see that the C7 and C8 layouts are actually rotated 180 degrees from one-another. So on the trailer connector you need to cut off the locking tab, the outer-edge keys, plus one center key. It will then plug cleanly into the C8 position, upside-down. You can pull the blue locking tab on the trailer connector, then use a small screwdriver to pop out the individual connectors and rearrange them as you wish. A carpet knife works well for the surgery.

One other thing that's easy to access is the dimmed instrument lamp feed. There is a pin on connector C5 of the MBEC, also normally unused, that carries this. C5 is the 2nd-from-the-right connector position on the top row. The instrument lamp power is on pin F, the lower right pin. An alternate place to tap into this same line is the unused PTO connector. (I'm assuming here all of the trucks were built the same as mine). When used, the PTO switch replaces the cubby in the lower-right instrument panel. I think the airbag switch is there on extended-cab models. The connector is taped and hanging behind this cubby. You can get to it by removing the cubby, or by dropping the glove box door and reaching in a little to the left. It's an 8-way connector, smaller than used in the MBEC. The wires going to it are yellow, black, blue, brown(x2), green, brown/white, and grey. If you look at the face of the connector with the locator tabs up, the instrument lamp power is in the second-from-the-top position on the right hand side, which is pin C. It's the brown wire with the white tracer. I used a pin from a "snappable" header to plug into it, but any solid wire of the appropriate size will work.
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2003 GMC Sierra D/A CC LWB 4WD
Fold-a-cover tonneau
2003 Cougar 278EFS 5th wheel
 

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Thanks

Thanks for the tips guys. The Electrical pins were right where ya'll said. Just took good ole female connectors, squeezed them in a little and they fit nice and snug. Drilling the Exhaust manifold was simple. I probablyy should have spent the buck and a quarter on the SD intake manifold for the fittings, but my tap into the Alum pipe is secure and should be fine for years to come.
The biggest headache frankly, was the stupid mount I got. I bought the overhead above the mirror thing. A POS frankly. It is impossible to mate it up tight enough so there is not a little seam so the instrument back light doesn't shine back through the crack. And the little Velcro attachment to the windshield is a joke. I need my little cubby up there so will put a piller mount in next week.
 

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Just a word of caution,

You should use a volt meter to test circuits for power, sometimes circuits are energized by grounding something out which is what you will do with a regular test light.

You could (but not likely) trip your air bag to deploy.

So unless you have one of the test lights that is powered and grounded and made for newer cars or a voltmeter you might be playing with fire using a regular light bulb test light.

DD

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Above the mirror gauge pod

Thanks for the tips guys. The Electrical pins were right where ya'll said. Just took good ole female connectors, squeezed them in a little and they fit nice and snug. Drilling the Exhaust manifold was simple. I probablyy should have spent the buck and a quarter on the SD intake manifold for the fittings, but my tap into the Alum pipe is secure and should be fine for years to come.
The biggest headache frankly, was the stupid mount I got. I bought the overhead above the mirror thing. A POS frankly. It is impossible to mate it up tight enough so there is not a little seam so the instrument back light doesn't shine back through the crack. And the little Velcro attachment to the windshield is a joke. I need my little cubby up there so will put a piller mount in next week.
Interesting comment about the over the mirror gauge pod. I was considering using that as the Trippin plate won't fit the 06 with a sun roof. Looks like I will be using a pillar mount. Anyone else have any experience with the over the mirror mount.

Thanks.
 

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Just a word of caution,

You should use a volt meter to test circuits for power, sometimes circuits are energized by grounding something out which is what you will do with a regular test light.

You could (but not likely) trip your air bag to deploy.

So unless you have one of the test lights that is powered and grounded and made for newer cars or a voltmeter you might be playing with fire using a regular light bulb test light.

DD

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Alright you scared me and I dont really want to buy a volt meter. Has anyone installed gauges using the C8 Pin C (upper left pin in C8) for power, and C5 Pin F (lower right pin in C5) for Dimmed lights in a 2005? Should i be safe just wiring them up and testing?
 

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Don't be scared just be careful.

You can get a cheap voltmeter at Sears Hardware.

If you do use a test light just be careful at what your poking. ;)

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Anyone try'd using the above rear view mirror gauge holder from autometer recently? Just ordered a 2 gauge one, hope it works good.
 

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I have a 4 guage holder that I have not installed yet but I did trial fit it and it looks like it fit's pretty well.

.
 

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If you guys are insterested I've went through the upfitter schematics and documents most of the pins in an openoffice spreadsheet so I don't have to hunt around with a meter to find what I want. If there is somewhere on this site to upload it I can do that.
 

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I used a fuse tap,there is a fuse that is for the instrument panel lites and uses the dimmer,it is located in the fuse panel on the left side of dash.Surprised no one else has used this fuse,really simple to get at and easy to run wire up to gauges.
 
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