NewB here and I know this topic has been beaten to death but I need clarification and help.

Installed new Alpine 9884 HU, F250 amp and Infinitis front and back in my 1996 C4. SYS light came on so I did a search and found that it has to do with an open dimmer wire circuit. Ripped open dash and connected gray wire to the orange dimmer wire on the Alpine HU. SYS light went away and auto dimmer feature on new HU now working when head/park lights turned on. Took my Vette for a drive at night and the SYS light reappeared. Pretty consistent cycle.

Did more searches and came across a post where someone had issue with SYS light coming on when he put his thumb over what appears to be a light sensor on the dash above the DIC buttons. Next DAY unhooked battery to reset computer (not sure if that really works) and SYS light was gone. Drove for a while and remembered light sensor post and thought I would see what would happen. SYS light reappears when I covered it with my thumb. SYS light is definitely related to this (ambient?) light sensor on the dash. SYS light comes on every time I cover it or drive at night.

Is there another wire in the original harness that I need to attach to the orange dimmer wire or another wire on the new HU? I have seen the resistor schematic but have no idea how to read it or if it applies to my situation or if the (ambient?) light sensor issue has anything to do with the aftermarket install. I am guessing it does since the problem arose immediately after the install.

Please help as the SYS light is really annoying even though it only comes on at night or if i cover the sensor. I was just beginning to really enjoy and trust this car.

 

http://www.corvetteforum.net/c4/dave8476/index4.shtml pretty sure this applys

 

I don't think this resistor fix applies in my situation.

I have connected the gray illumination wire to the orange dimmer wire on the new HU and that function is working. Is there another wire that needs to be connected to the orange dimmer wire on new HU too?

 

What' the deal with the purple/white wire on the original harness. Could this be my issue. Do I need to do just the one resistor? and to what wire do I connect that resistor to? (purple/white => resistor => ?wire)

 

well in the diagram it talks about hooking 2 resistors, so they must each serve a purpose, you prly need 1 still

 

Is this the case even though my new HU has a a dimmer feature which is connected and working?

 

There are two wires being sent from the control to the radio. One dims the LED, the other dims the LCD. They are two different circuits, that's why you need two resistors.

If your illumination works, then you still need to add a resistor to the other line to satisfy the circuit.

Mark

 

So do I connect the purple/white wire to the orange dimmer wire on the new Hu? Or do I connect the purple/white wire to a resistor to a switched power wire?

 

Updated my post:

There are two wires being sent from the control to the radio. The Purple/White dims the LED, the Grey/Black dims the LCD. They are two different circuits, that's why you need two resistors.

If your illumination works using the Grey/Black wire, then you still need to add a resistor to the Purple/White wire to satisfy the circuit.

Go to Radio Shack and buy a 1000 ohm, 1/2 watt (or bigger) resistor. Connect it to the Purple/White wire, and connect the other end to a switched 12 volt source.

You can probably connect it to the red wire at the HU wiring harness. (Red = Switched. Yellow = Constant) Use heat shrink tubing and/or electrical tape to prevent any short circuits.

If you cannot read the schematic, and aren't proficient with electronics, you may want to consider taking your car to a professional.

Mark