I know that there have been a lot of posts on this subject but I haven't read any that have given me an answer to this problem. Here goes--

My father is the owner of this 86 Corvette that is having this problem.
Digital Dash will work for a few days and then go blank..Dash has been sent out and repaired twice late last year.He sent it off the first time and once we got it back and installed it, it worked good for a few days and then started doing the same thing again. So Dad sent it back to the guy and he checked it all out and made sure everything was working properly and verified the power supply was working good...
Found a loose ground wire on the passenger side interior-- was re-grounded. Not sure if that had any relation to the problem or not.
Positive battery cable was unhooked for a few minutes and reconnected. Dash worked good for a few days and then it was back to blank.. What would make it do this? It sounds to me like something is resetting internal which lets the dash display normally until it decides to go blank again... ??

Another ground wire was added into the ground wire ( not sure which ground it was ) and grounded to a separate place...

My question is could this possibly be the ECM acting up or is there still a ground wire issue that I am missing somewhere?? Car only has about 78K miles on it... the dash issue started last year.
I haven't taken a good look at the ground that is connected to the bellhousing bolt ( 3rd one up close to the top of the engine )

On a separate note and possibly related to this, the Volt/Water Temp display is acting weird. The volts reads around 17 volts and when switched to water temp, it will read the temps for a few mins and then go back to the Voltage reading.. Alternator was tested and is good...I verified that it was putting out the proper voltage at the back of the alternator with a voltmeter.

Any help on this is greatly appreciated. Thanks in advance!

 

If there is a problem with a reading the dash will switch to that reading and show a red light to tell you something is wrong.

In this case 17 volts is too high so the dash will switch to the voltage display to show you the bad reading. I don't know what the threshold high voltage is, but I found out today that it will switch to voltmeter if the voltage is below 11.5 volts (flakey alternator in my car).

One possible problem with your blank display is a bad connection or connector. Many times the dash can fail with an overheated solder joint on the connectors, but if the dash has been sent out for repair this should have been corrected if it was a problem.

One thing I have seen is that the tang that locks the connector pins into the connector shell can be bent or otherwise fail to hold the pin in place. Pull on all the wires to make sure the pins don't come out of the connector shell.

 

When you say blank does that mean no inputs from the gauges or absolutely nothing as no lights and no readings? There are more than one power systems running this display. The back lighting is a 12 volt system. The gauges are governed by the sensor readings and the voltage varies. I believe the circuitry is mostly 5 volts and the LCD's are run with a higher voltage from the onboard power supply. I would keep chasing grounds. Cliff's suggestion of checking the pins of the 32 and 24 pin input connectors is a good one. There is also a 10 pin Molex connector between the two circuit boards that is a trouble spot, which ended up being my issue. You may actually do better replacing the display all together if it has solder joint issues. If you have replaced not repaired already, then your issue is with the car not the dash. If your alternator or voltage reg or rectifier bridge is having issues it will lead to all kinds of problems with electronics of the car.

Read here at batee.com for the most complete info on early digidash.

http://www.batee.com/corvette/

 

What I did was resoldered the cracked solder joints and replaced the caps on the power supply. Its almost 95% dried capicitor in the power supply. Change out the caps and should work like new. Figure the caps are 20 plus years old they dry up.

 

MiNe ToO...

 

Testing an alternator at idle may still check good even though it's bad. If your internal voltage regulator is bad on the alternator it may be making 17 v at 2K rpm and normal 14v at 600 rpm. This was the exact problem with my alternator before I replaced it.

I also had dash problems. Here is a link to my FB:
Pic Album

In there you will see what I found when I had to repair my digital dash. The problem was a melted bad ground at the 10 pin molex connector inside. Problem from too much juice from the bad alternator. I also found someone had been in there before and jumper-ed a circuit chip with a fuse. I removed that as well. Haven't had any problems since I repaired my gauges and my alternator.