24volt, converter to 12 volt radio power? (1 Viewer)

[Paul Rowand]

hello, I am installing a new radio, in my 24 volt BJ42 1981. I have a converter and want to know where I get the power from?
The fuse panel, or the Ignition ACC line, or the power to the ignition.....?
Any suggestions much appreciated.

 

[Living in the Past]

Believe most modern electronic audio units actually use two power sources. One that provides most the power that supplies the amp and holds memory for radio station. Then a second source thru the ignition switch to turn the unit on. If you ignition is still 24 volts I would use that to operate a relay with 24.volt coil. Then take you power that is not switched and branch a lead going thru the new relay normally open contacts. Some OEM type units actually have a third input that dims the lights in the face when the head lights are turn on. That would require a second relay to work. Not sure if it's a wire that with nothing hooked light in the face would just stay brighter.

 

[Paul Rowand]

OK.....
not really doing anything with the lights. Just a radio, My Ign, is 24volt......i am running it to a high capacity converter, down to 12 volt. I was mostly interested in where to get the power from, as I can not find any details on where to get the power first, before the converter....?

 

[Living in the Past]

OK.....
not really doing anything with the lights. Just a radio, My Ign, is 24volt......i am running it to a high capacity converter, down to 12 volt. I was mostly interested in where to get the power from, as I can not find any details on where to get the power first, before the converter....?

Wasn't talking about doing anything with head lights. I know my modern vehicles the lights in the face of the head unit dim when the head lights are turned on. For your stepdown transformer from twenty four to twelve volts I would use it's own fused circuit back to the batteries. Not a fan of putting of adding a load to factory wiring. The relay from the ignition switch was so it would power on and off with the ignition switch but not run the entire load thru the switch. If you just running some period correct radio push button radio stations that is mainly there for looks ignition switch is probably fine. A modern unit you actually want to listen too will probably have a switched lead and a non switched lead. Beside losing the radio station every time you turn the switch off I wouldn't draw that much power thru an ignition switch.

 

[Paul Rowand]

Wasn't talking about doing anything with head lights. I know my modern vehicles the lights in the face of the head unit dim when the head lights are turned on. For your stepdown transformer from twenty four to twelve volts I would use it's own fused circuit back to the batteries. Not a fan of putting of adding a load to factory wiring. The relay from the ignition switch was so it would power on and off with the ignition switch but not run the entire load thru the switch. If you just running some period correct radio push button radio stations that is mainly there for looks ignition switch is probably fine. A modern unit you actually want to listen too will probably have a switched lead and a non switched lead. Beside losing the radio station every time you turn the switch off I wouldn't draw that much power thru an ignition switch.

OK....great, I understand what you meant now.......
The new radio is modern, so maybe giving it its own power might be best....just have to remember to turn it off all the time....

 

[Living in the Past]

OK....great, I understand what you meant now.......
The new radio is modern, so maybe giving it its own power might be best....just have to remember to turn it off all the time....

It your radio has two power inputs you can easily solve having it go off with the ignition switch using a isolating relay. A relay that the coil is twenty four volts and has just a normally open single contact that closes when the ACC circuit is powered on with the ignition switch. This is a very simple relay that just keeps twenty four volts and twelve volts from mixing.

 

[Paul Rowand]

It your radio has two power inputs you can easily solve having it go off with the ignition switch using a isolating relay. A relay that the coil is twenty four volts and has just a normally open single contact that closes when the ACC circuit is powered on with the ignition switch. This is a very simple relay that just keeps twenty four volts and twelve volts from mixing.

might be a bit complicated for my simple mind.......I bought a 24-12 high capacity converter, so I was just going to run the 24, from the igniction, to the converter, then to the radio.....
sound good....?!!

 

[Living in the Past]

might be a bit complicated for my simple mind.......I bought a 24-12 high capacity converter, so I was just going to run the 24, from the igniction, to the converter, then to the radio.....
sound good....?!!

No. It will put the whole load thru your ignition switch. The radios Toyota used when these were new were very low power consumption compared to modern radios. Would post a picture of your radio wiring hook ups and go from there.

 

[Paul Rowand]

No. It will put the whole load thru your ignition switch. The radios Toyota used when these were new were very low power consumption compared to modern radios. Would post a picture of your radio wiring hook ups and go from there.

good points........
so, then right from the fuse panel, with another inline fuse...?
so it would be direct wired to the 24v-12 converter, then to the back of the radio.......
sound good...?!

 

[bigtreads]

good points........
so, then right from the fuse panel, with another inline fuse...?
so it would be direct wired to the 24v-12 converter, then to the back of the radio.......
sound good...?!

Run a dedicated new wire to the battery at the 24 volt side, then to a new inline fuse, then to your converter. From the converter you will run one 12 volt wire for main power. To power on and off with the ignition key (so the main power can stay connected to keep your settings but not drain your batteries by staying fully "on") you will need to use a 24 volt relay to send 12 volt power to the "power turn on" wire on the stereo when key is on. So wire from key switch to 24 volt relay - wire from 12 volt side of converter to relay then from 12 switch side of relay to "power turn on wire" - also a ground wire for 24 volt relay. Sounds like a lot but really not hard one step at a time.

 

[Engineer8000]

what @bigtreads said.