Battery cutoff switch and cd player memory

[pat]

Im going to put one of those battery cutoff switches under the dash for safety and security reasons.
I know Ive seen something before that prevents the memory on my cd player from being wiped out evertime the power is cutoff. Anyone know what Im talking about?

[Brad]

I've heard of using a 9V battery hooked up to an old cig lighter plug-in from a cd player, but I never got that to work for me. I think there's another way by running a wire directly from the battery to the cd player or something like that. Other people should chime in shortly with info on how to make this work.

[sneakysnake]

Just use a small wire 16-18 ga. to loop around the cutoff, It will supply the memory power but will burn into if you try to start the truck.

[67ChevyRedneck]

Originally Posted by Brad

I've heard of using a 9V battery hooked up to an old cig lighter plug-in from a cd player, but I never got that to work for me. I think there's another way by running a wire directly from the battery to the cd player or something like that. Other people should chime in shortly with info on how to make this work.

I've always run a wire from the battery to the unit. I've done it on my 67 and my old 86 toyotas. No problems out of either. The one in the 67 has been connected for almost 10 years.

[pat]

Originally Posted by sneakysnake

Just use a small wire 16-18 ga. to loop around the cutoff, It will supply the memory power but will burn into if you try to start the truck.

Is this what you mean? Im thinking putting in a 20watt or so fuse in that wire would be better, It could power the radio but would blow when trying to start the truck with the batt cutoff switch open, right?..

[sneakysnake]

YES, A fuse would allow you to replace it if you ever forgot to switch the master.

[Chevyman680063]

I've been wanting to put a cut-off switch on my truck as well. Does anyone have any idea as to how much a cut-off switch cost and where to get one?

[Longhorn Man]

Something that could be done that would possably be better, or at least nicer...
Put a forrd type Starter relay inline between the battery(s) and the starter, wire the trigger wire to a push button under the dash. Pres the button as you turn the key, and it starts like normal. If you don't press the button, it'll just click, like if you had a dead battery. You could get real slick and mount the button on a fabbed plate on the brake pedal. Hold the brake down as you crank it, or just clicks if you don't hit the brake. I've seen this done where the cigarette lighter completed the circuit, but I don't recall how the heating element was bypassed to complete a circuit.
However, by going this route, the whole vehicle is still wired up, you can liten to the radio, the dome light will still work... 4 ways.. etc. You are ONLY inturupting the main cable to the starter, the rest if the truck is untouched.

[JustLiveIt]

Is this a newer style radio with a yellow memory wire?

If so, why not just run a separate wire, say 18ga, to the battery to power the memory circuit on the radio? Then you won't have to carry a box of fuses around with you to replace the blown one when you forget flip the cutoff switch.

Just be sure to fuse the 18ga wire within 12 to 18 inches of the battery. Should not need a large fuse, 5 amp will do.

In your pic all the power to the truck would go through the small wire if you forgot to flip the switch. If you use a 20 amp fuse with an 18ga wire you may heat the wire up pretty hot if you turned on an accessory that needs less than 20 amps with out flipping the cut off switch. The 20 amp fuse would allow all that current to go through the 18ga wire possibly melting it. 18ga wire is only recommended for up to about 16 amps for chassis wiring.

Mike

[smbrouss70]

Originally Posted by Longhorn Man

You could get real slick and mount the button on a fabbed plate on the brake pedal. Hold the brake down as you crank it, or just clicks if you don't hit the brake. I've seen this done where the cigarette lighter completed the circuit, but I don't recall how the heating element was bypassed to complete a circuit.

Here's some wiring diagrams from a .pdf that I have that shows how to do the cigarette lighter trick with the lighter being operable or inoperable.

If anyone would like the entire .pdf which is full of various uses for automotive relays (neat ideas for starter kills, simple alarms, etc.) send me a PM with your e-mail address and I'll send it out. Be forewarned though it is almost 3MB!

[VetteVet]

If you are doing this to prevent a thief from stealing your truck then you're wasting your time. I could defeat any of these ideas and have your truck running in less than 30 seconds and so could any thief. VV

[67chevy2wd]

You need to break the actuall posative or negative battery cable to slow the theifs down.

[smbrouss70]

I know you can't "stop" them, just trying to slow them down a little. If they really want it, they'll get it.

[pat]

Originally Posted by VetteVet

If you are doing this to prevent a thief from stealing your truck then you're wasting your time. I could defeat any of these ideas and have your truck running in less than 30 seconds and so could any thief. VV

Im mainly going for this on the advice of the shop that helped build my truck. He said he almost had one of his rods burn up b/c of an electrical problem and suggested I do this just to be safe. I plan on getting a good alarm, which I know probably wont stop a professional thief either, but what can you do.

[Fred T]

Originally Posted by pat

Im mainly going for this on the advice of the shop that helped build my truck. He said he almost had one of his rods burn up b/c of an electrical problem and suggested I do this just to be safe. I plan on getting a good alarm, which I know probably wont stop a professional thief either, but what can you do.

Since fire prevention is part of your goal, don't simply use the bypass fuse around the switch. It will allow an electrical fire anywhere in the truck. Go with the fused wire directly from the battery side of the swich to the radio.

There are two styles of mechanical switches. One replaces the positive battery cable clamp, and has a green knob to turn, cost is under $10. The other is a large, rotary switch that mounts in a panel. This is a far better switch, but also costs much more. I haven't bought one in years, so I don't know the price. Both should be available at your local mom & pop parts store.

[pat]

Originally Posted by Fred T

Since fire prevention is part of your goal, don't simply use the bypass fuse around the switch. It will allow an electrical fire anywhere in the truck. Go with the fused wire directly from the battery side of the swich to the radio.

There are two styles of mechanical switches. One replaces the positive battery cable clamp, and has a green knob to turn, cost is under $10. The other is a large, rotary switch that mounts in a panel. This is a far better switch, but also costs much more. I haven't bought one in years, so I don't know the price. Both should be available at your local mom & pop parts store.

Ok. This looks like the route I will go with. I dont have my truck close to me right now, but should a new cd player have a wire that is power all the time to keep the memory? Because I dont want the radio to stay powered on all the time.
Also, when running the wire before the switch I can use it to power an alarm as well as the radio memory right?

[smbrouss70]

yes, there are 2 power wires to "newer" radios. One for just the memory, and another that is switchable with your ignition.

Yes, you can use the same wire to run your alarm also. The memory lead on your radio draws VERY little amperage so you shouldn't have any problems.

[JustLiveIt]

Originally Posted by pat

Ok. This looks like the route I will go with. I dont have my truck close to me right now, but should a new cd player have a wire that is power all the time to keep the memory? Because I dont want the radio to stay powered on all the time.
Also, when running the wire before the switch I can use it to power an alarm as well as the radio memory right?

Any 1990's CD player and newer should have 2 wires for power. The yellow one is "hot all the time" for the memory and the red one is switched by the cars ignition switch or a switch of your choice to control when the radio can be used. Usually the radio will have fuses for these power wires close to the radio. However, for any long wire runs from the battery you want a fuse or circuit breaker at the battery too to prevent a possible fire. Say you accidentally cut the wire and short it out between the radio and the battery while doing other work on the truck. The fuse at the battery would protect you by cutting off the current.

You can use the "hot all the time" wire to power an alarm too that you put under your dash. Just make sure you use the appropriate wire gage and fuse rating to handle the alarm's current needs as well. A five amp fuse and 18 gage wire is plenty if you just want to power the radio's memory. Increase that if you hook up the alarm too.

Mike

Edit: smbrouss70 you beat me to it!

[smbrouss70]

Sorry!

Yours was more in depth, though.

[pat]

Awesome! I think thats everything I needed to know. Once I find some time to get it done Ill let u guys know how it went.
Thanks a lot

[Longhorn Man]

Here is a question... or rather a comment...
A properly fused electrical system CAN'T be the fault of a fire, so if you do up your harnesses right, and have the right guage wire, then there is pretty much no risk.

[pat]

Originally Posted by Longhorn Man

Here is a question... or rather a comment...
A properly fused electrical system CAN'T be the fault of a fire, so if you do up your harnesses right, and have the right guage wire, then there is pretty much no risk.

True, but I dont trust myself and after I smelled my neutral switch melting Ive been nervous about it ever since.