clock / preset wiring on a radio

[Topsterguy]

I have a disconnect switch on the negative termainal on my battery ( crank the knob back to cut the power) and I'm wiring in a stereo now. There's a wire that is supposed to go to a constant power source to keep the station presets etc  when the power is off. What's the best way to wire this in?  Thanks!    Larry

[crdnblu]

The easiest way to provide constant power to your radio memory lead is to convert to a positive side (+) battery terminal disconnect, with an attached fused "pigtail" connected to the radio memory lead.  (See attached link:)

http://www.oreillyauto.com/site/c/detail/LIT3/ATD300BP/N0362.oap?ck=Search_N0362_-1_-1&pt=N0362&ppt=C0061The%20fuse%20size%20required%20would%20be%20specified%20in%20your%20radio/stereo%20instruction%20manual;%20(they're%20typically%20a%203%20amp%20fuse.......)My%20understanding%20is%20that%20some%20racing%20organizations%20specify%20a%20[i]negative[/i]%20side%20(-)%20battery%20cutoff%20switch,%20but%20for%20everyday%20vehicles,%20or%20street%20rods,%20positive%20side%20cutoff%20works%20just%20fine.

[crdnblu]

The easiest way to provide constant power to your radio memory lead is to convert to a positive side (+) battery terminal disconnect, with an attached fused "pigtail" connected to the radio memory lead.  (See attached link:)

http://www.oreillyauto.com/site/c/detail/LIT3/ATD300BP/N0362.oap?ck=Search_N0362_-1_-1&pt=N0362&ppt=C0061

The fuse size required would be specified in your radio/stereo instruction manual; (they're typically a 3 amp fuse.......)

My understanding is that some racing organizations specify a negative side (-) battery cutoff switch, but for everyday vehicles, or street rods, positive side cutoff works just fine.

[enjenjo]

Wire the radio ground directly to the battery. Install a very low amperage fuse in the ground wire, two amps at the most. That way if you happen to turn on the key without turning on the battery disconnect, it will blow the fuse, rather can fry the radio.

[crdnblu]

My concern in specifying a positive side battery cutoff is that you can't always isolate a car radio/stereo form a chassis ground.  Many times, the stereo GND wire gives a better ground to ward off static interference, but the radio is still attached to the metal chassis of the vehicle, & not isolated, even if the radio GND wire isn't connected.

[Topsterguy]

The easiest way to provide constant power to your radio memory lead is to convert to a positive side (+) battery terminal disconnect, with an attached fused "pigtail" connected to the radio memory lead.  (See attached link:)

http://www.oreillyauto.com/site/c/detail/LIT3/ATD300BP/N0362.oap?ck=Search_N0362_-1_-1&pt=N0362&ppt=C0061

The fuse size required would be specified in your radio/stereo instruction manual; (they're typically a 3 amp fuse.......)

My understanding is that some racing organizations specify a negative side (-) battery cutoff switch, but for everyday vehicles, or street rods, positive side cutoff works just fine.

That's the exact switch I'm using, but it specified to put it on the negative side so that's what I did. the terminal hole is also a lot smaller so it will only fit the neg termainal. So you're saying I should change it to the pos side and hook the radio wire up to that fuse wire?

[crdnblu]

There are differences of opinion on this, (Google the question, & you'll see), but I've found the POS+ terminal connection to be the most straight-forward for your radio memory application; that's what I've used over the years.........

[wayne petty]

i have a few questions..

do you plan on leaving the car for any length of time.. with the battery switch off..  days or weeks not hours..

please hook up your hand held digital volt meter  in 10 amp mode to measure the parasitic current draw on the car stereo..  some take way too much current.. probably because of an error in design..  i have found up to a 0.257mA  draw.. that is just over 1/4 amp.. on the memory wire..

should be less than 0.010 mA  

just a heads up..

somebody on a different forum ask about disconnect switches..

http://i1207.photobucket.com/albums/bb476/waynep712/disconnectswitchwiriringwayne_zpsc5377a58.jpg

there are push /pull to shut off rods available.   padlocks setups to lock the battery.

http://i1207.photobucket.com/albums/bb476/waynep712/pushrodbatterydisconnect_zpsf609fe5a.jpg

i was thinking that morse cables like a push pull PTO cable might be used so you can get the switch in a better location.. instead of a straight pushrod.