Aerog

I'm looking at a wiring diagram for a new Kenwood CD Deck and a question came to mind.

The "ACC" Line (RED, Switched +12v) is shown going directly through the ignition switch assembly (accessories line), and the Yellow continuous +12v is going essentially direct to a continuous +12v source.

Here's the question: when the ignition switch sends +12V to the ACC line does the radio derive its operational power from the ACC line (via the ignition switch assembly)? Or does the ACC line merely throw a relay in the radio causing it to pull its operational +12V direct from the yellow (continuous +12v) line?

I'm working on an older car and want to throw a relay in the mix to eliminate any chance of toasting the ignition switch assembly or wiring, but I can't find anything that says for sure which line (yellow or red) will ultimately be the higher current line.

Thanks!
-- Scott

Radio Joe

I just checked the Kenwood schematics I have for the KRC-3006 and the KRC-2007 (both tape decks) and it seems that the constant 12 volts is used mostly to keep power for memory, while the ignition wire powers things like tape motor, power antenna, etc. The current rating of these units is 6 amps if you have it cranked all the way up to max output (volume). If you think your ign switch will have problems with that, a relay isn't a bad idea.
although the units I have schematics for are older, i'm pretty sure its safe to say the ignition wire draws more current then the 12 volt constant wire for your radio. hope this helps-JOE-

Aerog

Joe:

Thanks for the info. I wish KW (and others) would include some actual schematics, or at least specs and ratings with their equipment.

I talked with a friend of mine that's a tickerer and ex radio tech. He had precisely the same question I did last year... He claims to have put an ammeter in line on both the red and yellow lines and found that the yellow (constant) actually powers the radio, while the red is a switch on/off line - very similar to what an AMP does.

For some reason I doubt that's true, but I'll take his word on it.

In the mean time I decided to just use a relay to pull power for both yellow/red circuits from the same source. Ordinarily this wouldn't be a big deal but I wanted to have the higher current lines in the car for future expansion.

Final installation went great by the way, radio sounds great and did the job. KW DMASK looks great in the convertible too.

Thanks! - Scott

92TripleBlack

The easiest way to find this out on any unit is to check the ratings of the Inline fuses. If the constant is rated something small like 500MA(1/2 an amp), it is just for the clock and presets. If the ignition fuse is rated low, it just switches on the radio and the constant takes over. Most radios use the first setup as it is less likely to inadvertantly drain your battery.

If you want to set up an ignition line that is high power, use the igniton you have to power a relay that will draw power straight from the battery. I wouldn't worry to much about it as most decks with built in amps don't draw very much current. If you plan to use the wire in the future to power a seperate amp, then I wouldn't do that either. Run the amp directly to the battery and not the wire harness. The amp will have its own relay and it will be turned on by the radio with a very small amount of power from the radio in the remote wire. If you wire an amp to the wire harness you will be crying from the noise and if you wire the constant wire of an amp to an ignition wire, you will hear the amp pop loudly as it turns on and it will burn out over time if it doesn't blow your speakers first.

Sum it up:
High power deck(built in amp) wire to ignition and constant at harness
(cannot draw more than rating on inline fuse, usually 6 amps which didn't hurt anyone)

Low power deck(seperate amp)wire deck to ignition and constant at harness
Wire amp positive constant to battery, ground to frame, and remote to deck

Hope this helps
92TripleBlack( An old installation buddy)

[Modified by 92TripleBlack, 11:31 AM 8/13/2001]


[Modified by 92TripleBlack, 11:32 AM 8/13/2001]

Aerog

re:The easiest way to find this out on any unit is to check the ratings of the Inline fuses. If the constant is rated something small like 500MA(1/2 an amp), it is just for the clock and presets. If the ignition fuse is rated low, it just switches on the radio and the constant takes over. Most radios use the first setup as it is less likely to inadvertantly drain your battery.


Agreed and thanks for the info - except that I've yet to see any schematics from Kenwood that specifies any fuse/current ratings. The installation is from scratch, not an add-on or replacement to an existing wiring harness so I can't rely on what was there (thus the question ).

Thanks - Scott

92TripleBlack

Usually there are inline fuses are on the new radio harness. Did you get a harness with the kenwood or were the original fuses cut off the kenwood harness? If they were cut-off, you can also check by turning on the radio without the constant hooked up. It should work fully except the memory and clock functions should not last after the Ignition is turned off. If this is the case, you have the higher power draw from the igntion. This is pretty standard for the industry but unfortunately there are always exceptions.
92TripleBlack

Aerog

Good point - never thought to just try one line or the other.

No - the Kenwood harness was a simple bundle of pigtails that go into a block connector to the back of the radio, but just the pigtails, no fuses to speak of.

The installation was in an older car so the existing wiring wasn't any help. Actually there wasn't any

What I finally did was to just use the relay in conjunction with the switch, so at this point it doesn't matter which wire carries high current (actually both can). They go to a common fuse now, and everything works pretty well.

I'm not sure why Kenwood (and JVC - I installed a JVC deck in a kitcar this spring) don't just put a decent schematic with useful information on it. They absolutely show fuses in their "wiring diagram" but with no current ratings at all. I'm not sure if this is a liability-dodge so they can't be "wrong", or whether it's just the way it's done.

Anyhow with suggestions from this and another forum I settled on the scheme I used and all works well... sounds great by the way, even without the amp (yet) - clear good sound even with the top down.