Is there a way to make a deck hold power on startup?

**Wiredwrx** · 03-31-2006, 01:16 PM

Originally Posted by greenman100

to give the starter the maximum output from the battery.

some stuff, like the engine computer, must stay on through cranking.

greenman is correct, unless you are asking why they would remain powered while cranking. Even then, he is correct. Some things the manufacturer needs or wants to stay powerd to start the car. In the past, headlights were a perfect place to grab this power, but it may not be so anymore. You could take it from the fuel pump circuit (but be carefull, if you blow the fuse, well, you stop running and lean out the engine, which could problematic). Check the door locks, they are usually a good place for switched "constant" power. You really just got to check the fuse box, it is hard to say, but please report back.

As for taking the highest rated fuse, that really isn't necessary. First, the acc wire for your stereo is most likely low power. basically, it just "flips a relay" in the stereo, and then grabs it's main power from the constant connection to the radio through the existing harness. I would be supprised if it draws more then 500ma on the acc wire. If you are worried, measure it with an AmpMeter.

Michael

**lostreception** · 03-31-2006, 01:41 PM

this is a really great solution i never thought of it before but the problem did bother me thanks guys

whats the easier way to make a stereo that turns off when the key is removed to stay on till the drivers door is opened?
ive always wanted that feature but could figure it out
i think i few relays would do it but i dont have any idea where to start

**Wiredwrx** · 03-31-2006, 01:58 PM

Originally Posted by lostreception

this is a really great solution i never thought of it before but the problem did bother me thanks guys

whats the easier way to make a stereo that turns off when the key is removed to stay on till the drivers door is opened?
ive always wanted that feature but could figure it out
i think i few relays would do it but i dont have any idea where to start

That is pretty easy as well. Will take some relays, and some wiring. If you like, when I get a chance, I will draw something up and post it. While there might be an easier way, I am sure mine will work.

Give me a little bit of time to get it done, I am at work

Michael

**rotarypower101** · 03-31-2006, 03:08 PM

http://www.the12volt.com/relays/page5.asp

Radio On Until Door Opened (Retained Accessory Power)

If you wish to keep the radio (or any other device that is powered by an accessory circuit) on until a door is opened, you can do so by creating a latch when the accessory is turned on with the relay shown below on the left, then breaking ground to the latch when a door is opened as shown with the relay below on the right. While this will keep the radio on, the entire accessory circuit will see 12V+ until a door is opened with the key in the off position.

If you want to prevent 12V+ from feeding back into the accessory circuit or have more than one device on this circuit and do not want all of them to stay powered, you can isolate the device you want to stay powered by cutting the accessory lead going to it and adding two 1 amp diodes and an additional relay as shown below. The first diode near the top left of the diagram is to prevent 12V+ from going back into the accessory circuit. The second diode between terminals 87 and 86 prevents the radio from pulling current through the first diode. If the second diode is not in place, the first diode will become toast. The additional relay is needed to prevent the radio from turning off when the key is in the accessory position and a door is open.

**Wiredwrx** · 04-02-2006, 06:32 PM

Originally Posted by rotarypower101

http://www.the12volt.com/relays/page5.asp

Radio On Until Door Opened (Retained Accessory Power)

If you wish to keep the radio (or any other device that is powered by an accessory circuit) on until a door is opened, you can do so by creating a latch when the accessory is turned on with the relay shown below on the left, then breaking ground to the latch when a door is opened as shown with the relay below on the right. While this will keep the radio on, the entire accessory circuit will see 12V+ until a door is opened with the key in the off position.

If you want to prevent 12V+ from feeding back into the accessory circuit or have more than one device on this circuit and do not want all of them to stay powered, you can isolate the device you want to stay powered by cutting the accessory lead going to it and adding two 1 amp diodes and an additional relay as shown below. The first diode near the top left of the diagram is to prevent 12V+ from going back into the accessory circuit. The second diode between terminals 87 and 86 prevents the radio from pulling current through the first diode. If the second diode is not in place, the first diode will become toast. The additional relay is needed to prevent the radio from turning off when the key is in the accessory position and a door is open.

Thanks for posting that.

Michael