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Question: '89 ALL DASH/INFO CENTER/SWITCH GROUP LIGHTS

LORR1943

Active member
Joined
Nov 7, 2005
Messages
40
Location
HOUSTON,TEXAS
Corvette
1987 BRIGHT RED CONVERTABLE,RED & BLACK INTERIOR,
ON MY '89 VERT, AT NIGHT, WHEN I PULL MY HEADLIGHT SWITCH ON TO PARK OR MAIN, ALL MY DASH LIGHTS(BACKLIGHTS) GO OUT. IT BLOWS THE INST PANEL LIGHT FUSE(3 AMP) AND IF I SHINE A LIGHT INTO THE PHOTO CELL, THE INSTRUMENT LIGHTS(GAUGE CLUSTER) COME ON TO FULL BRIGHT, JUST AS THEY WOULD IN FULL DAYLIGHT, BUT THE INFO CENTER, SWITCH PANEL, AND CLOCK ARE STILL OUT.
ANYONE HAD THIS INCIDENT? IF SO, PLEASE SHARE FINDINGS. THANKS!;help
 
Here's the schematic

89dimming.jpg


The INST LPS 3 amp fuse provides the 12 volts for the following items.

1) Backlighting for radio
2) Instrument cluster lighting
3) Header Map light/console illumination
4) Telltale (DIC) backlighting
5) Wiper switch backlighting
6) PRNDL illumination for auto trans.
7) Heater/AC control head backlighting

From the fuse, a gray wire runs to the bulbs. Since the fuse is blowing, the gray wire must be shorted to ground some where.

Have you done any work on the car before this problem occured?
 
LIGHTS GO OFF

Here's the schematic

89dimming.jpg


The INST LPS 3 amp fuse provides the 12 volts for the following items.

1) Backlighting for radio
2) Instrument cluster lighting
3) Header Map light/console illumination
4) Telltale (DIC) backlighting
5) Wiper switch backlighting
6) PRNDL illumination for auto trans.
7) Heater/AC control head backlighting

From the fuse, a gray wire runs to the bulbs. Since the fuse is blowing, the gray wire must be shorted to ground some where.

Have you done any work on the car before this problem occured?
NO, NOT TO THE LIGHTS. THIS JUST CROPPED UP ONE NIGHT LAST WEEK, I STARTED THE CAR, THE DISPLAY WAS NICE & BRIGHT, I PULLED THE HEADLIGHT SWITCH TO PARK LIGHTS & THEN HEADLIGHTS & ALL THE DASH LIGHTS,INSTRUMENT CLUSTER,WIPER,TELTALE,HEAT/AC CONTROL,PRNDL, 7 ALL WENT OFF. I PULLED OUT A FLASHLIGHT TO SHINE ON THE PANEL & MY DISPLAY WAS THERE, JUST NOT ILLUMINATED. WHEN THE LIGHT HIT THE PHOTO CELL THE DISPLAY LIT UP BUT NOT THE OTHER LIGHTS. WHEN I GOT HOME I LOOKED AT MY SHOP MANUAL & SAW THE SCHEMATIC YOU SHOWED BUT I NEVER FOUND THE PHOTO CELL ON ANY PRINT. AFTER READING THE DESCRIPTION OF HOW IT WORKS, I CHECKED THE FUSE & IT WAS BLOWN. I REPLACED IT & EVERYTHING WORKED FINE UNTIL TWO NIGHTS LATER IT DID THE SAME THING. NOW THAT I'VE STUDIED THE PRINTS & WITH YOUR HELP YOU SENT, I'LL BE ABLE TO FIND THE CULPRIT & I'LL LET YOU KNOW WHAT IT WAS. THANKS FOR YOUR INPUT. I'LL GET BACK TO YOU.
 
My guess would be the gray wire for the wiper switch illumination or the rear view mirror courtesy lamp that shines down on the console.

The wire insulation can easily be cut because of the metal around the door and the wire for the rear view mirror runs along the windshield frame.

The dash cluster backlight bulbs have two sources for power. The dimmer switch when in Park or Head position and as you discovered the photo cell circuit can vary the voltage depending on the ambient light. I also have not seen the circuit for the photo cell.

It's gong to take some patience and process of elimination to find the problem.

Batee's web site has some info. about the dash cluster.

http://www.batee.com/corvette/dcrg/index.shtml
 
EURIKA!

My guess would be the gray wire for the wiper switch illumination or the rear view mirror courtesy lamp that shines down on the console.

The wire insulation can easily be cut because of the metal around the door and the wire for the rear view mirror runs along the windshield frame.

The dash cluster backlight bulbs have two sources for power. The dimmer switch when in Park or Head position and as you discovered the photo cell circuit can vary the voltage depending on the ambient light. I also have not seen the circuit for the photo cell.

It's gong to take some patience and process of elimination to find the problem.

Batee's web site has some info. about the dash cluster.

http://www.batee.com/corvette/dcrg/index.shtml
MAN YOU ARE REALLY SOMETHING. WHEN YOU ASKED ME IN THE LAST THREAD IF I HAD DONE ANY WORK ON IT LATELY, I FORGOT THAT I HAD THE DRIVERS DOOR PANEL OFF LAST WEEK TO WORK ON THE DOOR SPEAKER. WHEN YOU MENTIONED THE WIPER SWITCH I REMEMBERED I HAD TO PULL THE SPEAKER HARNESS DOWN FROM WHERE IT WAS TAPED TO THE OTHER WIRE HARNESS. I HAVEN'T LOOKED YET(I WILL LATER TODAY) BUT I WOULD NOT BE SUPRISED TO SEE THAT THE WIRES FOR THE WIPER SWITCH HAVE BEEN PINCHED BY THE WINDOW REGULATOR SINCE I DIDN'T SECURE THEM AFTER WORKING ON THE SPEAKER. I KNEW I WOULD BE BACK IN THERE SOON TO REPLACE THE SPEAKER AMP, SO I DIDN'T TIE UP THE WIRES. I'LL CHECK THEM AND LET YOU KNOW.
THANKS AGAIN FOR THE INPUT! AS ALWAYS, IT'S GREAT TO BE A PART OF A GROUP OF GREAT GUY & GALS THAT LOVE CORVETTES AND ARE WILLING TO SHARE THEIR KNOWLEDGE. :beer
 
YOU MAY HAVE GOTTEN MY OTHER MESSAGE. IF SO THAT'S COOL!
I TOLD YOU I WOULD LET YOU KNOW WHEN & IF I FOUND OUT WHAT WAS BLOWING THE DIMMING LIGHTS FUSE. I FOUND A BARE WIRE UNDER THE CONSOLE, IT'S THE PRN123 INDICATOR LIGHT. IT HAD BEEN PINCHED BY THE SHIFTER. I REPAIRED IT, REPLACED THE FUSE & ALL IS WELL. THANKS AGAIN FOR THE HELPFULL INPUT!
 

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