Okay guys and gals - I'm looking to install a second fuse block under the hood that I can run my daylights, and fan off of. But I only want it to have power once the car is actually running, meaning after it's started and idling.

What I'm looking to do is run a large gauge wire FROM the aforementioned power source TO the fuse block, then from there, two smaller gauge wires to both the lights and fan. My questions:

1) Just how large of a wire do I NEED to run in order to avoid wires catching fire or slowly melting? What about to the fan and lights? Is there some sort of formula you can use to determine size of wiring depending on amperage running through it?

2) Where can I get this type of power - power only once the car is idling? From one of the posts on the starter?

I'm also considering using relays, but I'm not exactly sure how to run them.

Any other ideas or answers would be great,
Steve

 

1) This should be a semi-helpful guideline... http://www.powerstream.com/Wire_Size.htm

2) No clue... maybe get a delay timer powered by the oil pressure switch or fuel pump lead from the ECM to switch a relay. Just an idea...I'm not an engineer

 

Thanks VERY much - that site rocks.

Quote:

2) No clue... maybe get a delay timer powered by the oil pressure switch or fuel pump lead from the ECM to switch a relay. Just an idea...I'm not an engineer

Yeah, that's what I'm thinking. I've got a delay relay part bookmarked around here somewhere.

Thanks again for the reply,
S.

 

Another good source of info:
www.the12volt.com
I love that site, and they have a table showing current draw vs recommended wire size.

In my car, I installed a second fuse box under the passenger side of the dash to run extra electrical items. That way, it is separate from the stock box. I ran 4 gauge from the battery, through an inline fuse into the cabin. Then I got a stock fuse box from another GM car, and mounted a distribution block on top of that box. The 4 gauge wire runs into the dist. block, then splits to all the feed wires into the fuse box. Then I can fuse everything I want separately.
So far just have door popper solenoids (running on relays), hood scoop flap, and aftermarket cruise control.


Since you want everything to only operate when the car is running or in accessory, you'll have to get power from another line. A GM shop manual, or maybe even a Chiltons/Haynes will show you which wires are only hot during run/acc.

Personally, I would use relays for the lights and even the fan. Factory lights use relays. The website I mentioned does a very good job explaining their operation.

So short answer:
1. I use 16 to 18 gauge for most applications, but headlights might need more. I believe the stock headlights operate on a 20A circuit. My door popper solenoids use 30A and I used 16 gauge wires to the relays. No problem.

2. Use a shop manual to grab a power source from the bulkhead connector on the driver side firewall. At least one of those wires has to be a run/acc only, but then you'll be adding draw like your lights onto an existing circuit! I prefer using relays.

 

Hey Kanuck, thanks for the awesome info, I'm going to do some more reading and see what I can come up with.

Steve