I am going to be activating a couple of accessories with manual switches, initially a couple of fans attached to an upgraded heat exchanger, as well as the H/E pump, and maybe other accessories later.

First question is, what type of relay should be used for this function, and where can I get them? Any part numbers to look for?

Second questions is, where should I tap into +12v on my truck? I want to be able to activate power when the ignition is off.

Third question is, where should I mount the relays? Pics would be great if you have them. Thanks.

 

I would use the 30/40 amp automotive fuses. They will probably cover anything your can dish out. On the nelson harness they are mounted on the ecm cover. The black plastic one. Im assuming that the avalanches are set up the same. I haven't heard anything negative about pulling power from that little jumper box thats inline with the alternator wire. Its easy and still looks clean. An alternative would be to take it off the little power block for the underhood fuse panel. You have to take off the entire plastic cover assembly to see it I think. If you pull power from anything after that fuse panel it will likely shut off after 10 mins with that battery rundown protection.

 

www.waytekwire.com is a good source for electrical stuff. Radio Shack will also have the relays but the one I used didnt have the center pin which, depending on what you want to do, might or might not be a problem.

 

Excellent tips, and thanks for the link, those guys look great.

 

No prob

 

also check the sticky that F8L put in above. go to the auto parts and get a foglight relay. and in the link above there are a number of wiring schematics that will help out as well.