Hi guys. I hope someone can clue me in to something for my '02 E-150 cargo. I need to supply a 30 amp line to a new accessory I've just installed. I located the fuze box and there are some unused sockets but they're unwired and dead. I need to feed a hot wire to the box but I can't understand where to find one. It's very important that the power be OFF when the engine is off, even if I'm just in accessory mode etc. The owner's manual says fuze # 8 is for ignition so it might be a good choice; as long as I don't overload the circuit. Seems a little risky. Anyway, where can I hook up to power? All spare fuze box terminals are unwired. Any help appreciated.
Thanks.

 

If you're going to run something that draws 30 amps, I would actually rather use a relay and draw main power from the battery. Use the relay signal from any fusebox location(fuse 8, you say) which is supplied power in run/acc. One thing to remember in adding accesories straight to the fuse box is that the normal load on that fused circuit is going to multiplied by the load of your accesory once activated. You'll probably be blowing that fuse often when everything is on at the same time. The relay puts almost no load on the circuit but still allows you to operate a high current draw.

Good luck. It shouldn't be hard to find a relay kit with precise instructions on how to wire up.

 

Thank for your reply ft05. I was told this mustn't be wired into a relay switch (whatever that is) because it must not be live unless engine is running. It's a hydrogen generator which breaks H2O into two gases and feeds into the fuel mixture but does not store anything. So if engine is off I don't want to be spewing hydrogen gas as I sit in accessory mode listening to the radio. Also, the unused fuse sockets are unwired as well; no power there.

 

A relay is nothing more than an electric switch. When a small amount of power is applied to the windings, it closes the contacts which can carry large amounts of current. The relay is only activated when current is applied to the windings, so if you tap into your radio circuit, you'd have contact current only when your ignition is on. The contacts of the relay could be connected to the battery and to your hydrogen generator.

The fuse for your radio would supply only the power needed to activate the relay, and your existing fuse should carry this small additional load with no problem.

Your choice of the relay to use will be dictated by the amount of current you wish to supply through the contacts (in your case 30 Amps), so I'd play safe and use a relay with a "load" current rating of 50 Amps.

 

Check your owners manual for the carand find the computer or fuel pump fuse. These fuse will only be powered when the ignition is on (yes... if you put the key in the run position and do not start the engine then you will make H2!!). You can confirm that there is no power with a multimeter and turn ignition on and off. THERE AREat least 2 fuses that are live only when the key is in the run position, and will not be live in theaccessory position.Run a small wire off this fuse (you can buy clips that allow you to tap of the fuse it self) to a relay. (A RELAY is a switch that is turned on by appling voltage on one side, check one out at the local parts store you'll understand it). This is your triggering voltage, it flips the switch on for you when voltage is applied. Wire the other half to battery and H2 maker. The Relay will spell out the correct pins to attach the wires. Additionally, you may want to install an indicator light on the lead from the relay to the H2 generator to let you know when your making H2.

Good luck