Compuniac

Put a new OEM (Panasonic) and a scosche fai-3a converter unit in years ago. Ever since then the whole instrument panel goes dark when headlights are on and it is dark. Now I am putting in a new unit and researched the problem.

There is much talk about 90-93 SYS error and dimming problems on the panel with OEM radios and there is a fix posted with some resistors. Not exactly the same problem but very close.

So what is the right way of hooking up a new radio - when the radio only has connections for + constant, + accy, pwr ant, and of course Ground (and a thing for pwr amps that is not needed).

Connector C1 has yellow(hot in accy or run, radio fuse), Pink pwr ant, and Grey (interior lights dimming, and black Groudn)
Connector C240 has Brown(hot all times, hooked to light switch, and Orange(hot all times, ctsy clk fuse)
Connector C5 has was connected to the original 'display dimming output' which does not exist on the new unit.

I am a bit confused how to connect this and still have lights in the panel when driving af night




1989 Corvette Radio wiring

Cruisinfanatic

What kind of radio did you put in your 89?
If it's a stock 85-89 radio, that black wire out the back is not used

Compuniac

It is a cheapo Pnansonic with a scosche fai-3a converter. (updated the original post to be more clear)

Cruisinfanatic

unhook any dimming feature. Early C4's don't have it

Compuniac

Not sure you understand the problem.
Problem occurs because one of the circuits are open as the dimming feature is not hooked up to the new radio(as is doesn't have an input for it). That circuit needs to be closed. That is the fix on a 90-93 but doesn't work on an 89.

So it needs to be closed - but which wire and how - use a resistor as on the 90-93s`

I suspect the brown wire since it is connected to the light switch but what to with it...

JimLentz

What currently happens if you remove all the wires from the radio with the lights on? Do you have the C68 A/C?

Cruisinfanatic

like I said, Your 89 does not have a dimming wire to the radio. I don't understand what you hooked up.
I hate schematics

WVZR-1

If you'd post the model # of the radio you're attempting to install I'd think you'd have "correction" information quickly. I used "correction" intentionally. I'd also think the FAI-3A could have it's own set of issues for you're install. With a "cheapo" HU why the need for the FAI-3A. I ain't ever used one but I've friends that have certainly shared issues with their installs. None were C4

Do you have the complete instruction package for the FAI-3A?

Compuniac

I do - FAI is not the problem. For sure.
I really do not think it matters what radio but it is a Pioneer (and not a panasonic as I wrote before) DEH-4700BT.

The issue is how the car electronics behave when it is not connected as designed (in this case there not dimming function on the radio) - not the radio

Compuniac

Well - if you dont like schematics then you are probably not the right person to answer
The brown wire is connected to the light switch - I assume teh original radio will engage dimming when it is dark as sensored by the LRD in the panel AND the light switch is on.
There is a grey wire that has to do with some dimming AND the grey/white wire has to do with dimming and AC control? That is what the schematics tell me.

Compuniac

yes - the panel goes 99.9 black if it is dark out (does not dim if I shine a light in sensor on the panel or turn the headlight back off)

WVZR-1

I'd think you just use known supply to whichever wire to control the Pioneer lighting. I doubt you can establish dimming.

Compuniac

Execpt that is the whole problem. The circuit is open because there is no dimming on the radio. The open circuit 'confuses' the light switch wire (brown I suspect) because there is no where to hook it up!

WVZR-1

I changed my earlier post while you were doing this - I doubt you can control dimming unless there's multiple choice wiring for the Pioneer. I didn't look at the wiring schematic because I don't see an English option for the install, Portuguese I don't comprehend.

Only a WAG but with the radio being newer and BT etc that there's likely internal control for dimming! Do you have the "USERS" guide?

JimLentz

That circuit goes to other areas of the car, so having the wire to the radio disconnected for dimming should not cause a problem.

Compuniac

I have absolutely no interest in establishing dimming - I want to be able to see the instrument panel when it is dark and the lights are on.

Compuniac

*should*
this is exactly what is the problem on a 90-93 as documented in the FAQ.

WVZR-1

Later C4 with CCM etc are very different. If removing the "GRAY IP wire" does create an issue I'd think a quick check/test would be a bulb/socket to the wire and see if you get IP dimming back OR actually if you splice the GRAY to GRAY/WHT to AC control lighting I'd think you're back in business for all.