1990 C4 LCD display needs help
Thread Starter
Racer
Joined: Aug 2011
Posts: 494
Likes: 138
From: Chesapeake, VA
1990 C4 LCD display needs help
I need some assistance as I cannot find a sloution via search.
Problem is LCD panel displays perfectly fine with car not running as soon as engimne is started the entire LCD panel goes into a hieroglyphic dance routine. It unusable to drive.
I just got done disassembling the cluster, inspecting, cleaning ...... and reinstalling - No change.
I cleaned G201 - that helped my flaky A/C panel but no change to LCD dance.
I am stuck as to what to do next......my guess is the problem does not lie in the cluster since the issue is only with the car running. Please help.
Problem is LCD panel displays perfectly fine with car not running as soon as engimne is started the entire LCD panel goes into a hieroglyphic dance routine. It unusable to drive.
I just got done disassembling the cluster, inspecting, cleaning ...... and reinstalling - No change.
I cleaned G201 - that helped my flaky A/C panel but no change to LCD dance.
I am stuck as to what to do next......my guess is the problem does not lie in the cluster since the issue is only with the car running. Please help.
Burning Brakes
Joined: Nov 2008
Posts: 995
Likes: 1
From: Naples Campania
You have a ground issue. It's a tough thing to trace. Since it only happens when you start the car, it might even be caused by the alt or battery. A signal is probably partially grounded somewhere and is sending voltage back up into the display via the ground. Sound wierd, I know.
*edit*
Disconnect the alternator and start the car on battery. does it do the same thing?
*edit*
Disconnect the alternator and start the car on battery. does it do the same thing?
Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 8
From: Tampa Florida
I need some assistance as I cannot find a sloution via search.
Problem is LCD panel displays perfectly fine with car not running as soon as engimne is started the entire LCD panel goes into a hieroglyphic dance routine. It unusable to drive.
I just got done disassembling the cluster, inspecting, cleaning ...... and reinstalling - No change.
I cleaned G201 - that helped my flaky A/C panel but no change to LCD dance.
I am stuck as to what to do next......my guess is the problem does not lie in the cluster since the issue is only with the car running. Please help.
Problem is LCD panel displays perfectly fine with car not running as soon as engimne is started the entire LCD panel goes into a hieroglyphic dance routine. It unusable to drive.
I just got done disassembling the cluster, inspecting, cleaning ...... and reinstalling - No change.
I cleaned G201 - that helped my flaky A/C panel but no change to LCD dance.
I am stuck as to what to do next......my guess is the problem does not lie in the cluster since the issue is only with the car running. Please help.
http://www.corvetteactioncenter.com/...0/008/article/
Burning Brakes
Joined: Nov 2004
Posts: 897
Likes: 12
From: Land of Whiskey Rebels, PA
"Good job" to the writer.We need to stash that somewhere.
Thread Starter
Racer
Joined: Aug 2011
Posts: 494
Likes: 138
From: Chesapeake, VA
Yes.....that is why I had the cluster out
Thread Starter
Racer
Joined: Aug 2011
Posts: 494
Likes: 138
From: Chesapeake, VA
Okay tonight:
I ran with alternator disconnected - still did it.
I pulled CCM and cleaned contacts. Had codes 27, 32, 34, 36, 38, 7272, and 74. codes were gone upon reinstall and recheck.
Started car LCD still dancing
CCM - no new codes.
I am back to thinking cluster (LCD) is bad.......
I ran with alternator disconnected - still did it.
I pulled CCM and cleaned contacts. Had codes 27, 32, 34, 36, 38, 7272, and 74. codes were gone upon reinstall and recheck.
Started car LCD still dancing
CCM - no new codes.
I am back to thinking cluster (LCD) is bad.......
Instructor
Joined: Oct 2006
Posts: 225
Likes: 0
From: Washington NC
I have a 90 also. I cleaned the accessoy grounds when working on the airbag sensor on the driver's side. You have to remove the battery box to get to it. Grinded the chasis to bare metal, put some dielectric grease and it, and reinstalled. This fixed my dancing dash. Hope it works for you.
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Thread Starter
Racer
Joined: Aug 2011
Posts: 494
Likes: 138
From: Chesapeake, VA
Are you talking about the ground of many wires on the block near the oil filter? g107 or108 I think. I do see the group of power (fusible links) behind battery.
On another note - are clusters from 90 to 96 interchangeable? if no what fits and why?
On another note - are clusters from 90 to 96 interchangeable? if no what fits and why?
Instructor
Joined: Oct 2006
Posts: 225
Likes: 0
From: Washington NC
Beside the airbag sensor on the driver's side there are 2 grounds located within 6-8 inches from the sensor, those are the ones.
Racer
Joined: Aug 2006
Posts: 277
Likes: 8
From: Calgary Alberta
Don't know if this will help or not... I had a funky LCD display on my '90. Looked everywhere was about to pull the wiring harness. Phoned Gordon Killebrew, he told me to check/replace the coil ground inside the distributor... problem fixed.
Thread Starter
Racer
Joined: Aug 2011
Posts: 494
Likes: 138
From: Chesapeake, VA
Thread Starter
Racer
Joined: Aug 2011
Posts: 494
Likes: 138
From: Chesapeake, VA
I will definately have to look into that because I vaguely remember the speedo working fine when I test drove the car, then flatbed home, then stared parts replacing which included rotor/cap.
I wonder............
Thread Starter
Racer
Joined: Aug 2011
Posts: 494
Likes: 138
From: Chesapeake, VA
May be onto something here.......coil frame top quite rusty so I cleaned up spot for coil ground but that didn't stop the LCD dance.
I had left the coil cover off and I heard a strange buzzing sound so I got out and looked at the engine and I see a bright blue arc from the red coil wire to the coil frame as it's running - I guess that should be the source of my interference. Will pick-up new coil tomorrow and see what happens......
I had left the coil cover off and I heard a strange buzzing sound so I got out and looked at the engine and I see a bright blue arc from the red coil wire to the coil frame as it's running - I guess that should be the source of my interference. Will pick-up new coil tomorrow and see what happens......
Thread Starter
Racer
Joined: Aug 2011
Posts: 494
Likes: 138
From: Chesapeake, VA
apparently I am missing this ground strap too - didn't realize it when I replaced the cap. http://www.autozone.com/autozone/par...trap/_/N-9n8gz
- this will probably also explain the radio buzz and the occasional misfire in the engine too......
- this will probably also explain the radio buzz and the occasional misfire in the engine too......
Last edited by RedTRex; Oct 20, 2011 at 09:29 PM.
Thread Starter
Racer
Joined: Aug 2011
Posts: 494
Likes: 138
From: Chesapeake, VA
Fixed !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!
Damn......problem solved. Coil ground strap was missing causing coil red wire to arc to coil frame which caused some massive interference. I bought a new coil, which came with a ground strap I found out later but had purchased a new strap itself.
Sooooooooo....for all those who thought it was a ground problem (including me) good job..... tough one to solve though. Now I have 1/2 the dash to put back together.
Sooooooooo....for all those who thought it was a ground problem (including me) good job..... tough one to solve though. Now I have 1/2 the dash to put back together.
Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 8
From: Tampa Florida
apparently I am missing this ground strap too - didn't realize it when I replaced the cap. http://www.autozone.com/autozone/par...trap/_/N-9n8gz
- this will probably also explain the radio buzz and the occasional misfire in the engine too......
- this will probably also explain the radio buzz and the occasional misfire in the engine too......
That will do it The secondary coil ground is a pretty big deal - nice catch and good work! 
7th Gear
Joined: Sep 2019
Posts: 7
Likes: 0
From: Winston Salem, NC
