90 dash/climate/radio dim in daylight...H Code 74 in history - ZR-1 Net Registry Forums

Corvette95 · 02-13-2020

Need some help with this 90 I picked up. I have never owned a 90-93 , think I have or had every other year C4 except 84. The cluster and LCD are dim in daylight, as is the climate control and radio. It had a CCM code 74 in history, I cleared that and it didn't come back. I am using a FSM for a 92 as I don't have one for the 90 yet, only a preliminary which says the diagnostic tree "TBD". I think the lamps are very dim in daytime with lights off, but I suppose the 90 is just dimmer than my 95's? I have tried shining a flash light into the photocell, the lamps brighten up a little, much more with lamps on. I have turned the lamps on and covered the photocell with tape and verified the lamps dim. The dimmer switch does work and fluctuated the brightness. My lamp count is zero (Tech1a) with flashlight aimed at photocell and runs about 20-40 outside today which is a very cloudy day. I could pull out the radio and climate control and trouble shoot per the 92 manual, but I "guess" it will check out. Is this a known problem before I start taking it apart? I was thinking photocell but it seems it is working with an accurate count? I could put a resistor in the photocell but at 0 lamp count it wouldn't get any brighter? It is brightest with lamps on with flashlight aimed at photocell than any other circumstances. Any idea's?

PhillipsLT5 · 02-13-2020

From Dynomite Solutions
74 LED display dimming output circuit open or shorted to ground

Corvette95 · 02-13-2020

Quote:

Originally Posted by PhillipsLT5

From Dynomite Solutions
74 LED display dimming output circuit open or shorted to ground

I have searched for a specific thread on this but didn't find anything. I am more curious to know if anyone else has a dim 90 dash in daylight as the code 74 has not reoccurred.

Ccmano · 02-14-2020

Here’s the page from a 90’ Manual. That’s a history code which means the problem is intermittent. Follow the tree and let us know what you come up with particularly the diagnostic aids section.
H

Ccmano · 02-14-2020

I should add, a dim (washed out) LCD is common by itself. They can and do go bad. But it does sound like you may have a dimmer switch and or photo cell issue. I had a good LCD but a dim cluster. I ended up replacing the DIC with the photo cell and replacing the cluster with a rebuilt unit. Check out www.Batee.com
H

Corvette95 · 02-15-2020

Thanks for the manual photo, I have emailed Batee and waiting for reply.

Sent from my iPhone using ZR-1 Net Registry

02-13-2020	#1
Corvette95 Join Date: Jan 2006 Location: Decatur, AL Posts: 1,115	90 dash/climate/radio dim in daylight...H Code 74 in history Need some help with this 90 I picked up. I have never owned a 90-93 , think I have or had every other year C4 except 84. The cluster and LCD are dim in daylight, as is the climate control and radio. It had a CCM code 74 in history, I cleared that and it didn't come back. I am using a FSM for a 92 as I don't have one for the 90 yet, only a preliminary which says the diagnostic tree "TBD". I think the lamps are very dim in daytime with lights off, but I suppose the 90 is just dimmer than my 95's? I have tried shining a flash light into the photocell, the lamps brighten up a little, much more with lamps on. I have turned the lamps on and covered the photocell with tape and verified the lamps dim. The dimmer switch does work and fluctuated the brightness. My lamp count is zero (Tech1a) with flashlight aimed at photocell and runs about 20-40 outside today which is a very cloudy day. I could pull out the radio and climate control and trouble shoot per the 92 manual, but I "guess" it will check out. Is this a known problem before I start taking it apart? I was thinking photocell but it seems it is working with an accurate count? I could put a resistor in the photocell but at 0 lamp count it wouldn't get any brighter? It is brightest with lamps on with flashlight aimed at photocell than any other circumstances. Any idea's? __________________ Corvette95 Registry and Forum (*************) 1989 C4 Conv Wht/Gry Auto Hardtop Top Flight SOLD 1995 C4 Coupe Purple/Blk 6 Speed 1989 C4 Conv Wht/Red Auto SOLD 1996 C4 Conv Black/Tan Auto SOLD 1994 C4 Coupe Wht/Blk SOLD 1995 C4 ZR-1 White/Gry #278 Dual Dunn Head SOLD 1986 C4 Coupe Black/Red 4+3 SOLD 1990 C4 ZR-1 Red/Red #0454

02-13-2020	#2
PhillipsLT5 Join Date: Aug 2005 Location: Scottsdale, AZ Posts: 2,451	Re: 90 dash/climate/radio dim in daylight...H Code 74 in history From Dynomite Solutions 74 LED display dimming output circuit open or shorted to ground

02-14-2020	#4
Ccmano Join Date: Jun 2006 Location: Sparks, NV Posts: 2,852	Re: 90 dash/climate/radio dim in daylight...H Code 74 in history Here’s the page from a 90’ Manual. That’s a history code which means the problem is intermittent. Follow the tree and let us know what you come up with particularly the diagnostic aids section. H __________________ 90'ZR-1 #1461 Red/Black Ported Intake, Degreed Cams, OBX Headers & Exhaust, Fidanza FW, Secondary Delete, Custom tune, C6 GS Wheels. Sold 08 C6 Z51 Crystal Red Metallic Sold Vararam Intake, Tune, Sold 05 C6 Z51 Red/Black Sold 90'ZR-1 #1723 Black/Gray Sold but not forgotten 91' Z51 L98 White Vert. My First, you always remember your first. Sold.

02-14-2020	#5
Ccmano Join Date: Jun 2006 Location: Sparks, NV Posts: 2,852	Re: 90 dash/climate/radio dim in daylight...H Code 74 in history I should add, a dim (washed out) LCD is common by itself. They can and do go bad. But it does sound like you may have a dimmer switch and or photo cell issue. I had a good LCD but a dim cluster. I ended up replacing the DIC with the photo cell and replacing the cluster with a rebuilt unit. Check out www.Batee.com H __________________ 90'ZR-1 #1461 Red/Black Ported Intake, Degreed Cams, OBX Headers & Exhaust, Fidanza FW, Secondary Delete, Custom tune, C6 GS Wheels. Sold 08 C6 Z51 Crystal Red Metallic Sold Vararam Intake, Tune, Sold 05 C6 Z51 Red/Black Sold 90'ZR-1 #1723 Black/Gray Sold but not forgotten 91' Z51 L98 White Vert. My First, you always remember your first. Sold. Last edited by Ccmano; 02-15-2020 at 10:46 AM.

02-15-2020	#6
Corvette95 Join Date: Jan 2006 Location: Decatur, AL Posts: 1,115	Re: 90 dash/climate/radio dim in daylight...H Code 74 in history Thanks for the manual photo, I have emailed Batee and waiting for reply. Sent from my iPhone using ZR-1 Net Registry __________________ Corvette95 Registry and Forum (*************) 1989 C4 Conv Wht/Gry Auto Hardtop Top Flight SOLD 1995 C4 Coupe Purple/Blk 6 Speed 1989 C4 Conv Wht/Red Auto SOLD 1996 C4 Conv Black/Tan Auto SOLD 1994 C4 Coupe Wht/Blk SOLD 1995 C4 ZR-1 White/Gry #278 Dual Dunn Head SOLD 1986 C4 Coupe Black/Red 4+3 SOLD 1990 C4 ZR-1 Red/Red #0454