Hi guy, I need your help with something. I have a 1995 SC400 and I had a Kenwood Z828 installed by a buddy. Since that day, I could never get my dimmer **** working properly. What the **** is supposed to do is while it turns it brightens the instrument cluster, climate control, shifter labels, etc, until full. Then you can click it up to max intensity and it will make the instrument cluster very bright.

What my **** ends up doing is if it is not clicked on max, the instument cluster is blacked out, and the turning adjusts the climate control and all other lights. When you click it into max, the instrument cluster comes on at regular full brightness, and not max brightness. The other lights in the car are on at the same full brightness too. My Lexus tech told me the reason being is because whoever installed my deck did not bother connecting the dimmer circuits in the old stock stereo unit so the circuit is incomplete and unable to turn onto max brightness.

Well today I tried to fix the problem myself with the help of this wiring diagram: http://www.intellexual.net/faq/lexusstereo.swf . If you take notice on the A-harness, there are two leads for the illumination, A2 and A9. The Kenwood deck has one dimmer control wire (orange)--see attached Kenwood wiring diagram below. I tapped the A2 wire and spliced it to the orange wire on the Kenwood head unit. Unsuccessful.

My next idea is to join A2 and A9 into one disconnect and attach it to the orange Kenwood wire. I want to know if this is a good idea or will I potentially blow a fuse/fry my deck. Why are there two illumination wires on the one wiring harness? Should I just take the A9 wire and send it to the system ground so the circuit is complete?

What else could be going on? It seems from the strange behavior of my equipment lighting, that more is going on that just an incomplete circuit.

Thanks in advance for your help!

 

Oops, here's the Kenwood wiring diagram... This is for the Kenwood Z919, but it is essentially the same deck...

 

I just noticed that A2 = (Ill +), and A9 = (Ill -). What if I just stuck a jumper in between A2 and A9 pins? Would this complete the circuit?

 

lex, illumination circuts in aftermarket radio can either be + or - depending on the manufacturer. get a D.M.M. and tap the illumination wire on the head unit to see if it idles at 0 and goes to -1 or better (*negative ground potential) when the switch is on, or if it idle's at 0 and goes to +1v or higher when the switch is on.

test this with the dimmer off and then wide open. They seem to have gotten the + and - factory wires mixed up, but only the test will reveal that.

If you want a permanant fix, after finding out if the ill goes to +12v on the head unit, simply attach the wire to the 12v switched ignition wire and leave the factory lexus ill wires open and unattached to the head unit.

The head unit will illuminate, and the lexus lights should be as they are supposed to be. it sounds like the ground wire is reversed - basically they grabbed the wrong ill wire. if the kenwood works off -12v the +12v lead would screw up the rest of the system. same for the reverse situation. A simple head unit lead as described above from the ign. will fix that. unless it is a -12v ill wire, that is. then you'd obviously need to ground it all the time.

 

p.s.- when in doubt.... hit it with the juice. (you won't kill it)

snip the factory lexus wires free of the H/U's ill wire and stick +12v to it and see if it illuminates the faceplate of the headunit. then while the radio is disconnected, test the dimmer circut. (this will be important while you have all the wires open on pin a2 and a9)

 

PPS- i'm telling you all this because i don't know if you want a quick fix, or the real fix. the problem is this:

the dimmer works off of resistance. it is a variable resistor, or "pot". when more resistance is added the light becomes more faint, when less resistance is present, more voltage feeds the bulbs and illuminates better.

the problem here is that the wire they grabbed is feeding the dimmer switch with ground potential and the kenwood is increasing the resistance when it turns on. You have to get off the wire it's on toi allow the resistance to decrease and allow the lights to brighten back up. the other wire may not be the correct one either. you may not have a correct wire, since changing the ground potential affects the dimmer so much. in this case, you have no option but to wire into the ignition as stated earlier and leave the two wires (A9 and A2) open and hanging.

by testing as i stated above, it gives you the option to figure it out and do it right, before you "patch" it. though the patch is also the correct way of doing it, just not as far as the dimmer goes.

 

Thanks for the tips onelasttry, I lost my multimeter a few years ago, I'll have to buy another one. I knew I'd have to use that damn thing someday!

 

 

Would the diagram for the SC above work for a 1st generation LS without Nak?

Thanks in advance.

 

BLUE!

I just recieved the diagram i've been waiting for all year. the dimmer is BLUE.