I am wanting to add a key-on terminal block for stereo, lights, atc. I read an article that said I would need a starter solenoid... That didn't seem right to me, so how should I wire one up so that it only has power when the key is on? Thanks!

 

A few things to consider: A starter relay might work. All starter relays are not constant duty.
Figure the total load of all your future electrical additions and choose the relay to handle the total load. Amplifiers draw lots of current. The relay should be powered through the ignition switch. Choose a constant duty relay with small current draw at the pick coil and just heavy enough to handle the load of your accessories.

 

One suggested improvement: the relay contacts (the switch side, where the load current goes through) could be powered at the starter solenoid, but the relay coil powered through the ignition switch. This takes the added current draw away from the ignition switch, and the ignition switch only has to power the relay coil (minimal). The relay contact power (from the solenoid) would need to be fused directly at the solenoid, where it starts. This method would keep the block powered only when the key is on, since the relay would only close once the key is on. The relay would open once the key is off, shutting off power to the block. Just an idea.

 

you need a relay that has contacts rated to handle the total amp draw of all your loads if they were to run all at the same time then just power the relay coil from your ignition switch.

 

Check out my build thread. I added one when I installed power seats. It has 6 blade type fuses and is powered up "key on" by a relay under the hood that I installed. Here's a link and feel free to ask questions......I'll help you out.


https://www.ford-trucks.com/forums/1...4bt-build.html

 

Easy way to add power without changing much. This would be the basic diagram of what fmc400 and 78 PEB stated. You wouldn't necessarily need to access the fuse box for an ignition source, but that would be simple.

 

Great diagram, here's another way to look at it (showing the connections of the relay):



I've shown it as hot-in-run, but you could also tap into something that's hot-in-accessory. I like Buck's idea of getting the keyed signal from the fuse box because it'd be easiest, and powering the relay coil downstream of a fuse would be safest.

 

Thanks guys.........you saved me from having to draw it up. I picked up switched power from an existing connector under the dash in the area above the ignition switch about the height of the radio. Not sure what it was originally for, but made for a clean place to pick up switched power a bullet style connector IIRC. For the fused "hot" wire into the relay I picked it up off of the starter solenoid on the battery side. The fuse is one of the PAL? style 40A. My pics in my build thread show the style of fuse. Its pink in color. No butchery required!!!!!!!

 

^^^^ also nice diagram showing how the relay will work to power the accessory terminal block. I think doing something like this is a must for these trucks or at least in the plans unless the main fuse block has been upgraded. It takes away the hack job many do and in the long run cause many wiring problems in the future, especially if you have a bare bone truck.

78 PEB, I did take a look at your build thread and I have to say that is a very nice job on the seats and wiring.

 

So what kind of relay would I need? And how big of an inline fuse?

 

I used a 40A bosch relay. You can buy the molded connector to plug into the relay which makes it a cleaner install. Check NAPA and others. I used a 40 A fuse since I was using a 40 A relay.

 

You can use a standard 12-V automotive relay, rated to handle the load you will put on it. You will need to determine the current draw of each load (radio, lights, etc) and add all the currents together. Personally I would use a relay rated for double the current - others may have other opinions. For example, if you figure out that all of the loads together is around 20 amps, I would go for a 40 amp relay (others might feel fine with a 30 amp relay). I myself like the added safety margin and I'm willing to pay for it, but in some cases it's not practical to be that conservative. What I would do is figure out what your total current draw is and post that here, then everyone can look at it and tell you what they think. Keep in mind you may add devices to it later down the line, like a CB, etc. You'll want to keep some margin for that too - this is one of the reasons I tend to be pretty conservative here.

In addition to the relay rating, the current draw will also determine the gauge wire you use from the battery-side of the solenoid to the relay, and from the relay to the terminal box. The fuse should be sized to protect the wiring, meaning the fuse rating must be less than the maximum safe current draw of the wiring. I prefer to add margin here as well.

 

I have repaired so many "hack jobs" both during my job as a Heavy equipment and truck mechanic and in pursuit of my hobby (or disease whichever applies) that I REFUSE to do a hack job on anything I do, either professionally or personnaly. I try to make things look and work like factory installed. Keep watching my build. I'm working on getting the Cummins and ZF5 ready to drop in.......... And BTW thanks..............