Digital Cluster Repair Tips

From Bob Golden:

My name is Bob Golden and my home e-mail is . I wanted you to now how I enjoyed reading your publication on the repairs of the famous digital cluster.

For 20 years I was the General manager at Speeometer Service, Inc. in Carrollton Texas. It was bought out and is now called Autocraft. Their address is 1612 Hutton Dr. Suite 120 Carrolton, Tx.75006-6675. Phone 972-466-6200. They are one of the few left that still remanufacture Clusters for AC-Delco. They may be another source for you. I'm no longer there but I know the technical staff and they are very good.

I have attached a short help sheet I sent out to some friends and thought you may want to have it. If you contact Autocraft ask for Tommy Terrell. He was the original repairman that was used by Delco on these clusters. I remember they used to have some new clusters that were never used because they did not have cruise control circuits in them. You may want to inquire about these for parts. By the way the cruise control driver transistor P/N was 16008121 a number I came all too familiar with.

1984-1989 C4 Corvette Instrument Cluster Issues

Having your instrument cluster repaired or exchanged can be a costly item. If indeed you must have this done call the experts first. There are only a few authorized remanufactures still around that can do this type of work. Whichever you choose go direct and save. Ask your GM dealer for the AC-Delco remanufacturing center nearest to you. However, many times this is not necessary if you know the tricks.

LCD displays must have backlighting to illuminate. Many times all you need to do is change the bulbs. These bulbs can be changed by simply removing the plastic panel covering the instrument cluster. Pop out the metal bulb covers and with the use of some shrink tubing you can grab the bulb and work them out. Shrink tubing can be purchased at Radio Shack or any electronic supply center for peanuts. Buy the size that will fit over the bulb snuggly. After you have pushed it over the bulb, heat it for a very brief 2 seconds and pull the bulb out. To re-insert a new bulb use a similar method without the heat. Avoid touching the bulbs with your fingers. Body oil will causes heat spots and shorten the life of a bulb. These bulbs can be purchased through your GM dealers.

A better suggestion is to remove the entire cluster and replace both the sockets and bulbs. This requires a little more work but will address the intermitting type of display black out. You will have to remove the tin panel covering the back of the cluster however this is very easily done.

If you experience a complete blacked out cluster, check your ground first. The most common ground found to be loose is G401 located rear of engine below left hand valve cover and is sometimes disturbed during maintenance.

AC Display will not dim with dash lights**---This is another common complaint I have encountered. The dimming control for this display is controlled from and output of the radio.It is a pulse with modulation feed and if the factory radio has been changed out you will not be able to control the AC display.

Bose Radio Compliant—The speakers cut off and on at times. This may require amplifier repairs or replacement. However before you spend all you dollars for amplifiers try cleaning the tone controls.The Bose audio is a unique audio system. It requires total control over any pre-amp parameter. If the tone controls are scratchy, chances are they are causing the channels to drop out.Use a cleaner that contain a lubricant and spray a small amount in each control. Work them up and down a few times to clean the oxidation off. Again make sure you use a cleaner with a lubricant. If the controls are void of lubricant they will become very difficult to operate.

The most common complaint in the early years, especially 1984 was blank displays caused by a 50/50 tin content in the solder. (This was also why the early Bose amps quit and if you catch them in time they wont burned themselves up)) Simply re soldering the power supply connections usually cured these. There were two grounds that come out of the unit and sometimes just tying these together cure the problem of high gage readings. I'm sure more of this will come back to me as I go over the old schematics. The funny little connectors between the circuit boards and the LCD were called elastomeric connectors. A simple cleaning with contact cleaner was all they ever needed.