The Stovebolt Site Forums The Shop Area The Electrical Bay 6 volt relay switch

I plan to install a 10 fuse fuse box in my truck. I bought it at NAPA. The truck is 6 volts. I would like to connect it to the ignition so it is off when I turn off the truck. It wont have much running most of the time. Directional signal, backup lights, converter for cigerette lighter, etc. i believe I need to add a relay for full battery power.

Any suggestions?

no you don't need a relay, none of those items take enough power normally to need one, you just want to fuse them - you need to wire the fuse panel to an ignition switch terminal that's only 'hot' when the key is on, labeled ACC on many switches - if a simple switch with no labels [3 terminals?], use the same terminal that goes to the gas gauge, which is only on when the key is

Bill

Thanks Bill. I thought I needed a relay. I do have an ACC terminal.

Again, thank you

What size fuses will I need? I found some 7.5 amps

Hy oldbluetruck, six volt circuits require fuses twice as large as twelve volt circuits, half the voltage twice the amperage, that goes for wiring as well, larger gauge for six volt, hope that helps.

Thanks. So, what size fuse would you use for back up lights, heater fan, directional signals, or a cigarette lighter (used to charge a cell phone or power a gps unit) in a 12 volt system? I can double that for my 6 volt system. Again, I have 7.5 amp fuses now. They are from battery tenderer units.

Thank you

Think in terms of "work". That is the effort required to do something. OK, now think about Volts as "pressure" current as "volume". With twice the pressure you need 1/2 the volume to do the same work. With 1/2 the pressure you need 2 time the volume to do the same work. Fuse only sees the volume. So....6 volt head lights= 20 amps each. 12 volt head lights=10 amps each. 6 volt blower motor=40 amps and 12 volt would be 20 amps. Modern cars are 12 volt and head lights get pulled together. So 2 head lights at 12 volts =20 Amps. Are we having fun yet? This is not too hard just take your time and pay attention to the requirements of each item you are fusing. 6 volt wires are just fine for 12 volt systems. 12 volt wires might be too small for 6 volt systems. From 6 to 12 volt keep the wires and you will be OK. 12 to 6 volt change might take some wire changes. But most don't go from 12 to 6 unless they are restoring. Cigarette lighter will pull more amps than your phone charger. put in a 15 amp just to be safe. Heater fan, 30 amp. Turn signals, 15 amp. back up lights, 15 amp. Something like that. This is all for 12 volt systems. Double if you are 6 volt.

12 volt backup lights and heater take 9 amp fuses, almost all original 12 volt stuff is 9 amps except the 12V radio takes a 7.5 anp ..... if you use too high a fuse rating it may not blow when there's a fault - err on the side of caution, use no higher than 15 amp in anything unless it immediately blows on first use, than if you're sure the circuit is good [ohm check for shorts to ground], use 20 amp, but I'd say none of the things you list will need more than 15 except possibly the back ups depending on how big the bulbs are

let me emphasize that: caution is a smaller fuse rating, it's easier to change to a higher rated fuse than to replace wiring fried because the over-rated fuse didn't blow in time

Bill

red58 is right. I was just giving examples for thought.

Wow. That's a lot of information.

So I have a 'typical' fan motor. Meaning original. A guide b-31 with a big bulb (1156?). 7.5 amp fuses should burn out? I should go above 20? I guess I should check all the fuses under the hood. My truck has the 1948 fuse box.

Thanks

no, you shouldn't go above 20 unless you're sure the item needs it, as in draws over 15 amps -
no, 7.5's won't necessarily burn out, try them and see -
an 1156 bulb is common for 12V parking lights, not "big" and I believe the Guide 31 was used for parking lights in some years, 7.5 might do, 15 at the most
you could use a meter to find out how much current any item item draws, your phone charger should say right on it

Bill

Thanks Bill. I plan to use the 7.5s just because I have them. But was wondering if I needed to drop down to 5s.

Thanks again

Just wondering about all your 12 volt items you say ur useing, were is your 12 volts coming from, you stated that you have a 6 volt system, 1156 bulbs are 12 volt and be be very dim and your cell charger and radio are probably 12 volt also. Acc power from ign switch to fuse panal is correct, but were is the 12 volts coming from. My posts are going to be kinda speratic cause I am working most all day and night but I am an auto and truck electricain and have been for 30 years. So I like getting involved in this stuff.
Every thimg I've seen so far on this post is good, just getting confused about your 6 volt system and your 12 volt components. I have done several rewiring jobs that we changed out all 6 volt lighting to 12 and used step down voltage boxes to run original 6 volt ignition ect. but a 6 volts system with 12 volt stuff don't compuut.

My system is completely 6 volts. The bulb in the backup light is 6 volts. I don't know it's number (1156?).

yes, I didn't pay attention, 1156 is a 12V bulb, better check the number on it

Bill

Dennis,

What vehicle's back-up lamp are you using?

The 1954 6v Chevrolet passenger back-up lamp's bulb is 1134.

I had to go down to the garage and look.
I have an 1129 in it.

I am using a guide B-31 housing

1129 bulb, 6 volt 16.8 watts, draws 2.63 amps .... 1134 bulb, 6 volt 24 watts, draws 3.87 amps

P/E=I, so for either of those bulbs the 7.5a fuse will suffice

Bill

This is a good example. Is there any good rule of thumb for fuses?

In this case the fuse (7.5) is double the draw of the bulb (2.63). Well, a little over but that's OK.

Should the fuse be double like this?

Thanks

Dennis,

One or two backup lamps/bulbs?

not necessarily, the 'double' suggestion is comparing 12V to 6V because 6V draws about double the current, forget the "doubling" and just deal with 6V item specifications - the fuse should be a size above the rated draw, usually you just use an available standard size above the items rating, 4,5,6 amp fuses aren't common sizes, 7.5 is, and you have 2 back up lights, not just one? ... you want to avoid using a fuse way above the item rating, like not a 30a fuse for the lights, try to find the amp draw of anything you use and fuse it slightly above that

Bill

One backup light. So, I should go down to a 5.

Thanks to all on your help.

Yesterday I hooked it up and it worked great.