LT SPD

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.

Eakster

Bump for you..

I was reading about this very issue today - about to do a HU install myself also. Did you have the Bose unit or the Delco?

I also read about the resistor fix but thought it applied to the Bose only - I could be wrong.

Here's the fix for it that you mentioned (if someone wants to explain it in layman's terms)

And here's the thread I got it from.

You'd be better posting in the Audio section under Corvette Forum general.

post up when you've fixed it! (with pics)

LT SPD

This was a non-Blose system. I have read about that resistor fix but I am under the assumption that fixes the circuit when the aftermarket HU has NO dimmer/illumination unit. I have connected the gray wire to the new HU orange dimmer wire. Does the purple (or some other) wire need to be connected too?

My SYS light only comes on when the (ambient?) light sensor is covered or at night. Otherwise the SYS light goes away.

94flavette

This happens to me as well in my 94 so I'm

...and, you have a '96, so the resistor fix doesn't apply. Those only affect the 90-93 models.

RandyJ75

You have it backwards, you need to do the resistor fix, when the lights come on, the ECM is looking for the draw of currect the dimmer would need. When its not there, it sets the SYS light.
Go to the Audio section and read the C4 FAQ, complete writeup in there.

Good luck,

Randy

LT SPD

Randy,

If I do the resistor fix, what do I do with the orange dimmer wire on the new HU? The dim feature is currently working on the new HU as I have it hooked up now to the gray wire on the original harness.

drojt

I had the same issue but finally fixed today!

Per other threads, yes, connecting the purple/white and gray/black wires to resistors per the schematic (TSB) works. However no one has articulated where these cables are.

Here is the solution:

1. Locate the purple/white and gray/black wires from an OEM input wiring harness that connects to the original radio. You may have to look for it but please note that it is separate from any aftermarket wiring harness (my mistake!). Mine was located very close to the firewall directly behind the radio and led to the driver’s side.

2. Next extend the ends of both resistors (1K Ohm .5watt) via 14 gage wire (I used a soldering gun and extended mine 4 inches on each end). Connect one end of each resistor to the power supply lead (preferably the AC Switch) and the other ends..one to the purple/white wire and the other to the gray/blk wire.

3. Cover all wires / reconnect the battery cable and you are done!

This process took me approximately 30 minutes and was rather easy once I figured out what I was doing.

Hope that this helps those who are having similar trouble.

Dave84/76

Here is the TSB for the SYS light fix: http://www.corvetteforum.net/c4/dave8476/index4.shtml
Connect the Orange wire from the new head unit to the parking light circuit. Should be a Brown wire in the car.