GMC 3500

KuhnElectronics · Post by **KuhnElectronics** » Sat Jul 23, 2005 7:46 pm

In reference to the GMC 3500 in my other post I have a few questions:

Looking for a good firewall access point

Looking for a good ignition point

The red box near the alternator, this is probably where I will get B+, what size stud is it, so I can make sure I have a few before next week.

I need to run some wire to the utility body from the console, is there a grommet or access to the rear, or do I need to make my own?

Does this truck have DRL, I was just wondering about wig-wags.

If anyone else could think of something on this truck I should be aware of that I havent mentioned I would greatly appreciate it.

Thanks,
Nick

007 · Post by **007** » Sat Jul 23, 2005 11:30 pm

KuhnElectronics wrote:
The red box near the alternator, this is probably where I will get B+, what size stud is it, so I can make sure I have a few before next week.

You need to make a new harness if you plan on using that power point for anything more than 5 amps. The alternator cable is only 10ga or 8ga going into that box...you need to upgrade.

KuhnElectronics · Post by **KuhnElectronics** » Sun Jul 24, 2005 5:24 am

Well..hmm.. I only got a chance to glance at this truck the other day.

So if I do not use this point, would it be easiest to just use a connection off of the battery?

or somewhere else?

Res168cue · Post by **Res168cue** » Sun Jul 24, 2005 6:31 am

"The red box near the alternator, this is probably where I will get B+, what size stud is it, so I can make sure I have a few before next week"

..... If its like any other GMC Truck or SUV its almost near impossible to get a connection off the battery due to the fact the the pos & neg leads are on the side of it that is facing the passanger compartment. I have used the "little red box near the alternator" tp power multiple lights/radios with no problems at all ......

..... As far as the daytime running lights go on the GMC's they are a serparate light from the headlights/highbeams. This being the case when it comes to choosing a WigWag or headlight flasher for the vehicle you can go with almost anything and not be stuck with something that will interface with DRL's ( I use a Whelen UHFPOS Headlight flasher positive switching )
P/N 01-0669129-000
S/N PNH04151

Hope this helps!

-Nate

KuhnElectronics · Post by **KuhnElectronics** » Sun Jul 24, 2005 10:12 am

Hmm.. well then I should be fine running a Whelen Edge, 6 LED's, 100 W Siren, and a CDM1250, right?

Do you remember what size the lug is, I am running low on connectors and Tessco hasnt sent mine yet, I hope they will be here tommorow, but just trying to be prepared.

- Nick

Res168cue · Post by **Res168cue** » Sun Jul 24, 2005 11:03 am

If you can get all of your power connections connected to the terminal... get to nut screwed back on... and close the cover again on the "red box" you should be more than good to go since thats drawing its power direct from the battery, power wont be an issue at all for you.

I'm not sure what size the lug is off hand but i do know that I have needed a 17mm socket to get the nut off the "positive post" inside the "red box"

Also if you are looking for a place to go through the firewall, there should be a 4" diameter gromit with a wiring harness coming through it in the back right corner of the engine compartment... take a razor knife and make a clean slice in the gromit on both the engine side and cab side... then what i did is put a 1 1/2" diameter 4" long piece of PVC pipe through the firewall to run wires etc... through with ease. then just silicone around the pipe and your done.

( I can send you pictures of this if needed )

GoodLuck! - Nate

KuhnElectronics · Post by **KuhnElectronics** » Sun Jul 24, 2005 8:40 pm

If you would send pics please to Nick@kuhnelectronics.com

- Nick

KitN1MCC · Post by **KitN1MCC** » Mon Jul 25, 2005 5:38 am

The Red Box is the place to go (thats were the Plow guys attach there Plow Pumps to)

for a whole there is a dimple in the fire wall under a little cloth typr thingy. that is held in place with a fast nut

Dotn cut open the harness that can cause all kinds of goofy things

jeremycharris · Post by **jeremycharris** » Mon Jul 25, 2005 10:07 am

As for the B+ I take the extra effort to remove the battery and use a post adapter, its more effort but its easier when you need to add or take away epuiptment.... and you can pickup b+ switched at the fuse panel in the cab . for a pass through just under the steering column and an inch or two to the right from the inside is safe to cut... good luck

Res168cue · Post by **Res168cue** » Mon Jul 25, 2005 2:44 pm

KitN1MCC wrote:The Red Box is the place to go (thats were the Plow guys attach there Plow Pumps to)

for a whole there is a dimple in the fire wall under a little cloth typr thingy. that is held in place with a fast nut

Dotn cut open the harness that can cause all kinds of goofy things

Its really up to you what you want to do to the vehicle in the end.... As far as making a cut in the harness, its 4" in diameter if you are even somewhat competent which I'm sure Nick is its not a major problem I did it and its the best way to get through as far as location and room to work with. As far as the "red box" goes.... if you are looking for power that's it most definitely.
Nick I will send pic's of the firewall job in an email to you as requested.

-Nate

apco25 · Post by **apco25** » Tue Jul 26, 2005 7:30 am

The red box is actually a jump start tap since the battery terminals are somewhat tight next to the main fuse panel. I'd leave it as just that, especially if you plan on installed a grill mounted jump start lead.

Get the GM post adapters and go right to the battery. I have 2, 4ga leads coming off the battery for front and rear power.

There should be a 1.5" FLAT "dimple" in the firewall to the left of the steering column. Drill and punch here, insert grommet.

Alternatively you could drop down along the frame and come up through the floor pan as I did for the rear power lead. Obviously your cab is much smaller than the suburban so the firewall route may be all you need.

PVC pipe for a grommet????????????

Splat · Post by **Splat** » Tue Jul 26, 2005 7:40 am

I cut off the side terminal connectors and installed top terminal connectors. Made things a helluvalot easier. I ran all wires through the grommet in the lower right side of the firewall. Sealed it up with hi-temp silicon. I don't like connecting power to the aux power taps by the inner fuse box. Get alot of noise that way. I also added another 8awg to chassis ground. No problems so far.

Res168cue · Post by **Res168cue** » Tue Jul 26, 2005 1:10 pm

PVC pipe THROUGH a grommet.... not FOR

apco25 · Post by **apco25** » Tue Jul 26, 2005 2:12 pm

OK i missread, but that's still rather unusual. Why did you do it that way?

Res168cue · Post by **Res168cue** » Tue Jul 26, 2005 7:41 pm

I just figured it would be much easier to run wires though something along the lines of a conduit rather than through the grommet that seals the opening and when doing so crimps down on anything going through it. So basically its for ease of installation.

KuhnElectronics · Post by **KuhnElectronics** » Fri Jul 29, 2005 8:52 pm

I got the job done yesterday...

Pics soon to come, but I just got in Flint Michigan this morning and followed Tiger Woods around at the Buick Open all day...

It turned out decent, they made me make some compromises on stuff I didnt want to. I wanted more strobes and LED's but their budget didnt allow. They were happy, I was happy, and I guess that is all that matters..

Anyways...pics should be up when I am back in the office Monday morning...

Nick

EVModules · Post by **EVModules** » Sat Jul 30, 2005 7:16 am

If running heavier wire thru the firewall, get a conduit fitting that is threaded to take an electrical conduit nut on one side & the other is designed to take a solvent weld like irrigation piping. These are very useful and I use these when running heavy power wires, multiple wires, etc thru the firewall when working on command post installs, and so forth.

HLF trick. The connections are all under the engine compartment fuse block!!! Take off the half moon bracket with 13mm to allow the fuseblock cover to come straight off. They come off by pulling on the tabs that hold the cover down. Set aside...

Release the tab on the fender side and rotate the fuseblock up and towards the engine. The headlight wires are towards the upper left side of the fuseblock, you should see light green & dark green next to each other. Lt green goes to the left light & dk green goes to the right. Make the connections there and mount the HLF under the fuseblock!

Hope it helps,

GMC 3500

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