Battery shutoff switch/radio presets

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Chuckbizkits

Chuckbizkits

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I am running a battery shut off switch. Sometimes the car will sit for awhile and I'd like to eliminate battery drain. I would like to run a 5A fused, dedicated line from the + terminal on the switch to the radio (memory). If I do this I will have feed back back thru the line, keeping the main panel energized.

I need to wire in a diode. Can someone please explain EXACTLY how to do this? Does the cathode point towards the + battery or the radio? Do I use a 1N4000 type of diode? Thanks.
 
The main radio power is separate from the memory power so I can't see any reason a single dedicated line to just the radio memory will energize anything else. I also don't think you need a diode to isolate it. If you do decide to use a diode the anode is what gets connected to the battery positive the and the cathode (end with the stripe) goes to the radio. Only thing is you mentioned the 1N4000 series and using a 5 amp fuse. I think the 1N4000 is only rated at 1 amp. A 1N4004 is good for 2.5 amps. That's the limit of my memory on them. I have a Sylvania book down in the basement and can look up what it'd take to handle 5 amps but again I don't see why you'd need one.
 
One last note for reference. When using a diode in line to isolate something it won't hurt anything if you wire it backwards. It just won't pass power.
 
fishy68 said:
The main radio power is separate from the memory power so I can't see any reason a single dedicated line to just the radio memory will energize anything else. I also don't think you need a diode to isolate it. If you do decide to use a diode the anode is what gets connected to the battery positive the and the cathode (end with the stripe) goes to the radio. Only thing is you mentioned the 1N4000 series and using a 5 amp fuse. I think the 1N4000 is only rated at 1 amp. A 1N4004 is good for 2.5 amps. That's the limit of my memory on them. I have a Sylvania book down in the basement and can look up what it'd take to handle 5 amps but again I don't see why you'd need one.
Click to expand...

I should have mentioned my issue. I am running a battery shut off switch. It's been working great. I just installed my source unit/head. If I shut the battery off, I lose my memory, presets and clock. So I ran a dedicated, 5A fused line from the positive post of the shut off switch to the battery + wire (yellow) on the radio. Now when I shut off the battery switch the fuse panel stays energized. When I disconnect said line the battery shut off works fine. I think I am feeding back into the system.
 
Do you have the dedicated wire only going to the stereo yellow wire or is the yellow wire also connected to the fuse panel? I used to repair tv's and stereo's and install car audio and never saw one feedback if the memory wire was just ran to the battery but anything is possible. If that's how yours is there must be something in the stereo feeding back and the only way to eliminate that would be to put a diode in line with the stereo's main power wire. Of course that power wire draws a lot of current at high volume levels so a 1N4004 wouldn't even be sufficient. I'll PM you my ph # so if you want to call me and talk about it we'd probably get it figured out faster. Tracy
 
You can get those 9 volt battery deals to plug into your cig lighter for just this purpose of saving radio codes and other memory functions.
Advance auto used to have them, but you can find them on the web.
 

It sounds like your wire to the radio is bypassing the switch (we know that) but feeding the fuse box? Something ain't right. Diode or not.
 
fishy68 said:
Do you have the dedicated wire only going to the stereo yellow wire or is the yellow wire also connected to the fuse panel? I used to repair tv's and stereo's and install car audio and never saw one feedback if the memory wire was just ran to the battery but anything is possible. If that's how yours is there must be something in the stereo feeding back and the only way to eliminate that would be to put a diode in line with the stereo's main power wire. Of course that power wire draws a lot of current at high volume levels so a 1N4004 wouldn't even be sufficient. I'll PM you my ph # so if you want to call me and talk about it we'd probably get it figured out faster. Tracy
Click to expand...

if the wire to the memory is coming straight from the + on the battery and not tied to anything else, then it should not bleed any power back into the fuse panel. If you suspect the head unit, disconnect the other power wire from the head unit so only the ground and memory wire are connected, does that still bleed power back to the fuse box? I would suspect that someone pulled the memory power from the cigarette lighter wire and it may still be connected.....
 
cudaspaz said:
You can get those 9 volt battery deals to plug into your cig lighter for just this purpose of saving radio codes and other memory functions.
Advance auto used to have them, but you can find them on the web.
Click to expand...

Those work fine for short term, like maybe 24 hrs., then the little 9 volt battery is drained. Their really just to be used when servicing the vehicle because you don't usually have the battery unplugged long. If his is feeding back and energizing the fuse panel like he says it'd be lucky to work at all.
 
More power getting on the other side of the switch than the memory wire. Do you have a 4 pole switch? If you don't, the engine won't shut off with it, as the alternator supplies current. Maybe that is it. The 12v memory is feeding things on the off side of the switch, as the alternator circuit needs to be killed, with the switch.
 
Thanks for all the insight.

I figured it out. I tested the continuity between the yellow wire (Batt +, memory) and the red wire (ACC +). There was zero resistance. So the constant power sent to the yellow wire was feeding through the rest of the rest of the system.

I talked to the manufacturer and they said that is not right. I am sending it in and they well test and send out another.
 
What other items do you have that draw current when the key is off other than the radio? If that is it, you accomplish nothing by adding a bypass around the battery shut off. Just leave the battery connected.
 
dgc333 said:
What other items do you have that draw current when the key is off other than the radio? If that is it, you accomplish nothing by adding a bypass around the battery shut off. Just leave the battery connected.
Click to expand...


- I am running a battery shut off switch. Shuts off power to everything.
- I want to save the memory presets and clock on the radio.
- I ran a fused wire from the + side of the battery shut off switch to the batt + (memory) wire on the radio.

What I am accomplishing is that no other circuits are getting power like the compressor for the air ride or the power door locks. Yet, the memory on the radio is still intact.
 
Chuckbizkits said:
Thanks for all the insight.

I figured it out. I tested the continuity between the yellow wire (Batt +, memory) and the red wire (ACC +). There was zero resistance. So the constant power sent to the yellow wire was feeding through the rest of the rest of the system.

I talked to the manufacturer and they said that is not right. I am sending it in and they well test and send out another.
Click to expand...

Sounds like a defective radio. Glad you found the problem.
 
Chuckbizkits said:
- I am running a battery shut off switch. Shuts off power to everything.
- I want to save the memory presets and clock on the radio.
- I ran a fused wire from the + side of the battery shut off switch to the batt + (memory) wire on the radio.

What I am accomplishing is that no other circuits are getting power like the compressor for the air ride or the power door locks. Yet, the memory on the radio is still intact.
Click to expand...

But those items don't draw current when they aren't being used. In your original post you stated your are trying to eliminate battery drain when the car sits. By bypassing the battery disconnect to the radio memory you will have the same amount of battery drain when the car sits. Unless of course there is a short or faulty component somewhere. In that case you should be trouble shooting that and fixing it, those are the kinds of issues that will leave you stuck on the side of the road at the most inopportune time.
 
dgc333 said:
But those items don't draw current when they aren't being used. In your original post you stated your are trying to eliminate battery drain when the car sits. By bypassing the battery disconnect to the radio memory you will have the same amount of battery drain when the car sits. Unless of course there is a short or faulty component somewhere. In that case you should be trouble shooting that and fixing it, those are the kinds of issues that will leave you stuck on the side of the road at the most inopportune time.
Click to expand...

See above. The battery drains when the air compressor runs due to the air bags fluctuating due to weather, etc. Also is a bit of a security device for the power door locks.
 
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