stereo reboots when key position changes

My car has this annoying issue, I suppose it could also be a design flaw in the head unit. I couldn't find any evidence of anyone else having this kind of problem but it bothers me and I'd like to fix it. I've got Kenwood DNX5210 (it's a double-din DVD/NAV unit) installed in my 95 Nissan 240SX SE. Whenever I turn the key from "ON" to "ACC" (for instance: I park and I'm listening to the radio, I want to turn the engine off but continue listening) the head unit will reboot as if I shut the car off completely and turned it back on again. I wouldn't mind a hiccup in the audio but being a more complex head unit I end up having to wait 30+ seconds for the thing to reboot before I get my audio back... so my choices are to either miss out on the next half-minute of the program I'm in to or sit there with the car running while I waste gas and fill my garage with fumes. It doesn't do this when going from "ACC" to "ON", just from "ON" to "ACC". I've never had (or at least I've never noticed) this happening in any other car. I don't know if the 240 did this before I put the head unit in either since I installed the thing a several years ago right after I bought it. ------------ I was thinking it could be caused by one of three things: 1. the ignition switch is warn out and has a dead spot that drops power for a split second. 2. the relay that controls ACC power is super sensitive and cuts out at the slight fluctuations from the ignition switch output when changing state. 3. the head unit lacks a power smoothing capacitor so it becomes sensitive and cuts out at slight fluctuations from the power input. ----------- I was wondering if anyone has dealt with this kind of issue before and if so, what did you do to solve it? I was considering putting a smoothing capacitor on the 12V ACC line going into the head unit to absorb these kinds of hiccups... and in the course of writing this post I started thinking about checking the ACC relay to see if it has a feedback diode, and either swap to a relay with one or add the smoothing cap to the coil input to produce a slight buffer. Any suggestions or advice would be appreciated, thanks :)

There is a diagram on here for adding retained accessory power under the relay section. I would just stick that setup in and not worry about it if everything else is working.To master and control electricity is perfection. *evil laugh*

What is the source of power and ACC power to the head unit?Support the12volt.com

racerjames76 wrote: There is a diagram on here for adding retained accessory power under the relay section. I would just stick that setup in and not worry about it if everything else is working.

That's actually not a bad idea. I was thinking about wiring something to work similar to my wife's Mini-Cooper which sustains ACC power until you open the door, I'll need to find and take a look at that thread though it seems like the door setup might require some logic beyond what you can easily do with relays.

DYohn wrote: What is the source of power and ACC power to the head unit?

It's the factory wiring, there's nothing fancy with the head unit wiring I just soldered up a METRA adapter pigtail. I just took a peek at the factory service manual and it seems that there's no relay in the stereo circuit at all, the power is routed straight through the key switch to a 10A fuse and then to the head unit.

If you do not feel like using the 2 relays for the RAP setup, you can use a diode and a 1000 microfarad capacitor.   Very simple and all parts available at radio shack. Diode in series with car acc wire and red wire of your deck. Band toward the radio. At the connection of banded end and radio wire, also connect capacitor positive connection. Ground the negative capacitor connection. This will keep the radio on for a second or 2. Plenty enough time to get your key turned back. Use a 3 amp diode. Rad Shack should have them in stock. https://www.the12volt.com/relays/page5.asp#drto

i am an idiot wrote: If you do not feel like using the 2 relays for the RAP setup, you can use a diode and a 1000 microfarad capacitor.   Very simple and all parts available at radio shack. Diode in series with car acc wire and red wire of your deck. Band toward the radio. At the connection of banded end and radio wire, also connect capacitor positive connection. Ground the negative capacitor connection. This will keep the radio on for a second or 2. Plenty enough time to get your key turned back. Use a 3 amp diode. Rad Shack should have them in stock.

I probably have most of that stuff in my parts bin already, I'll look a little further into whether the RAP setup will work for me and failing that go with the diode/cap. I'm planning to pull the car apart this weekend anyway to install some new satellite radio equipment, which is kind of why I created this topic, so I can kill 2-birds with one stone. Thanks for the suggestion! :)

You can also see simple switch with relay. That describes the common technique of "diode-ORing" inputs via (eg) 1N4004 diodes to a relay. EG - IGN and ACC so that - assuming either or both have power during switching - the relay remains energised including when cranking. Plus optional other inputs like a manual switch, or alarm +12V output, etc. Just connect all together via diodes. (Hence the "logical" OR - it's on if A or B or C or D etc is on.) If however there is an interruption (break) when switching (IGN key from IGN to ACC), then yes - capacitor. That could be added across the relay coil. IMO we (repliers) are all saying the same thing but with different ways of going about it. I generally use diodes rather than multiple relays (though an extra relay for polarity inversion of "other" sources is excellent - maybe not as elegant as a transistor etc, but far simpler and generally more reliable, and far easier to replace!). But take note of the experienced replies above. (Yeah man, they're good!!)      FYI - a relatively small capacitor is needed to hold up the relay coil (60mA-250mA) compared to the load (several Amps). Hence the ideal is having or finding the relay used. But most like us use dedicated supplies from the battery - they add their own fuse (and relay) and cable. That's the cleanest power for audio and computers etc, and avoids OEM harness cabling issues (size, voltage drops, interference etc). IMO it's bad that the OEM has that glitch - even if OEM was an analog HU. But whoever said (in a recent the12volt reply) that my thinking is often ahead of what car manufacturers do must be delusional - and probably arrogant!

I agree that it's bad for an OEM to have that glitch, though with the car being over 16 years old I'm willing to give them the benefit of the doubt and say it's possible the switch is just getting warn down. I picked up a DSO Nano a while back so maybe I'll hook it up to the switch and see what kind of drop I'm actually getting when I turn the key. After reading through that relay page I'm definitely going to go with the 2-relay RAP setup to power the whole accessory circuit it makes the most sense. I might also look into moving window power from the "ON" circuit to the "ACC" circuit as that's another bit that has always bugged me.