Hi, I would like to know the best place to get a 12 volt ignition-switched source of power on my 2004 Chevy 2500HD Duramax.


I want this source to run a solenoid relay which will be used to isolate my trailer charge wire when the ignition is off. The source does not need to have a lot of current available, but I do not want to tap into some place that will have negative consequences on other components in the truck, such as any of the computer systems.


I thought at first that it would be really easy to find such a source. I started in the under hood fuse and relay center, and checked every point I could reach. I pulled most of the fuses and relays one at a time and checked for a source that was hot only when the key was on. No luck.


Then I went to the fuse panel on the driver's end of the dash and did the same thing. Again, no luck.


Finally I went to the relay panel which is under the dash above the brake pedal (it has a black plastic cover screwed over it). In there I finally found a pin in an unused relay socket that goes hot when the key is turned on (the upper left relay socket). I am currently using that pin to trigger my trailer battery charge solenoid.


What I don't know is if that is a safe place to be tapping in. I'm probably only pulling a couple of amps from there, but I don't know if that will affect any other systems in the truck.


Anyway, what I really want to know is where is the best place to pull a source of ignition-switched power. Can anyone advise?


If you could PM me as well as posting an answer, that would be super.


Thanks....

Two big wires under the steering wheel to the ldft, the heavy white and heavy brown are both switced hot.

I've utilized the fused circuit for the rear window wiper in my truck. Since there's no rear wiper on my truck it's an extra circuit.

Ox

big dog


there are plenty of switched fuses on the drivers side fuse panel. Ws Wipers for 1 its a 25 amp fuse and its fed by the brown wire that wickedsprint mentioned.


Also there are some smaller 10 amp fuses but i would stick with the wipers or cruise fuse and you can feed off the hot side of the fuse and put your own fuse inline that way you wont overload the factory fuse.


Diesel Dragon

The solenoid you are using wouldn't even draw an amp- probobly 1/4 amp or so. You should be good where you are hooked to, or you could grab a spot where deisel dragon suggests. A 1 amp fuse should be lots.

In reading the install instructions for my new Racor fuel filter kit, it referes to the two pink wires, on the bottom side of the underhood fuse panel (roughly in center area) as being ignition switched. Look at step 15, page 8 of the instructions (pdf link below). I would verify this first of course.





http://www.gasgasrider.org/racor_dmax_instructions.pdf

First of all, thanks to all of you for responding.


Regarding grabbing switched power off of the driver's side fuse panel, I tried several points there including ones suggested, and they were hot all the time. I concluded that they must be switched by the ignition someplace after the fuse panel. I will check again tomorrow, but I thought I was fairly thorough.


In reading the install instructions for my new Racor fuel filter kit, it referes to the two pink wires, on the bottom side of the underhood fuse panel (roughly in center area) as being ignition switched. Look at step 15, page 8 of the instructions (pdf link below). I would verify this first of course. I tried to get to the underside of that underhood panel. I broke the plastic catch pushing on it. I pushed and pulled, and it would not do more than wiggle. I figured I could get under it if I tried harder, but was afraid more stuff would break.


I'll check that brown and white wire under the dash to the left of the steering wheel, assuming I can find them. I want to power a couple more relays for power points under the dash for things like CB radio, etc.


My battery isolation solenoid may take a bit more than 1/4 amp, as it is more than just a relay. It is a big metal can like a starter solenoid that locks in with a thud when energized. It is rated to pass 150 amps. I assume the electromagnet that sucks the points together is pretty substantial. But I still don't think it uses much more than a couple of amps, and perhaps less.


Thanks again everybody.


I don't know why truck manufacturers don't mention in their manual where a guy should pull switched power from -- many owners need to add extra devices such as CB radios, stereo equipment, lights, etc, and it would be nice if they provided a switched power point to grab power for relays.


Later.....

big dog


If your using a large relay like a starter size relay for your trailer charger I would check with the manufacturer how many amps it is pulling to be energized. If its a large amount say more than 5 amps I would set up another relay under the hood to turn on your trailer relay.


And your windshield wiper fuse should be switched. Check again it should come on when the key is in ACC or RUN. If your relay dosent pull much current I would tap there on the hot side. Also if you need CONSTANT 12 volts the ACC 20 AMP fuse in the fuse panel is another good place to tap.


Good Luck Diesel Dragon

A handy place to pick up a switched 12v lead for power relays is to use the yellow wire that goes to the windshield wiper motor. It's really handy. Goes into a hole in the firewall just above and to the left of the brake master cylinder. Has lots of slack to put in a splice. I mount my power relays for my ham equipment right on the firewall and then run 10 guage wire to the rigs. That orange box where the two batteries come together sure is handy for hooking the other end of the 10 guage.


I, too, thought about adding a relay to the Battery feed for the trailer connector. Beginning in '03, they made it very easy. Just remove that "J-Case" fuse that feeds the line. Underneath are 1/4" male spades to which you could attach wires to a relay. Just add a fuse inline.

Hey, I want to thank everyone for the great answers -- several good places to get switched power.


I did find some information that some of you may be interested in. It turns out that the place I drew switched power is just fine -- it is a place GM provided for secondary equipment outfitters to interface with the truck. The connector where I am connected is called the SEO connector (Special Equipment Operation) -- I'm on pin C, which as you can see in the diagram below is exactly where GM intended folks pull ignition switched 12V for secondary equipment relays. The way I connected to the pin is by using a female push-on connector, modified with a pair of plires to fit tightly on the pin.


http://home.comcast.net/~netboy/SEO-Connector.gif


I found the above information here: http://www.gmupfitter.com/publicat/pub.htm


Poke around there, and grab what you need before they decide to password protect the site.Edited by: big-dog1

big-dog1, do you know of a source for the actual connector as pictured? It would make accessory hookup simple. Thanks for the info! Edited by: jeephauler

big-dog1, do you know of a source for the actual connector as pictured? It would make accessory hookup simple. Thanks for the info!


No I don't. Yes, it sure would!


It may be worth an email to that Upfitter site where I got the electrical and chasis manuals (listed in my post above) -- I may check with them.


Cheers....Edited by: big-dog1

I solved the battery isolation problem by installing a second alternator, a single wire type, wired directly to the trailer charge circuit. With the engine shut off, no current flows in either directon. It has worked great for over a year now.http://www.dieselplace.com/forum/smileys/Big Smile.gif

I solved the battery isolation problem by installing a second alternator, a single wire type, wired directly to the trailer charge circuit. With the engine shut off, no current flows in either directon. It has worked great for over a year now.http://www.dieselplace.com/forum/smileys/Big Smile.gif


Wow, that is a slick idea. One nice thing about a 2nd alternator is you could put a smaller pully on it, thus getting higher charge rates at idle. With a remote starter on your rig, you could charge the batteries while laying in bed in the trailer.


I actually put the isolator solenoid back inside of my slide-in camper, and ran the activation wire into the camper through an unused wire in the triler wiring (high center brake light wire). Putting the solenoid inside of the camper let me wire a bypass switch around it, so if my camper battery goes low in the middle of a DVD movie (for example), I can enable the bypass and get juice from the truck for a while. I have a tag hanging on the switch reminding me to switch off the bypass.

big-dog1, do you know of a source for the actual connector as pictured? It would make accessory hookup simple. Thanks for the info!


Have you tried http://www.rockauto.com/ ?