Clusters & Controls
C4 Corvette Instrument Gauge Clusters & Dash Controls
C4 Corvettes had many designs of instrument gauge cluster and dash switches and controls. This guide is to cover those dash mounted items and their differences over the 1984-1986 production run. *Radios are not covered in this section.
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1984-1989 Gauges and Dash Controls
Air Condition Climate Control Units (84-89)
The A/C climate control panel has two main styles for 84-89 cars, the manual control (RPO C60) version and the automatic control (RPO C68) version that was available as an option from 86-89. Like other items there are more differences than just a manual and automatic version and these varied based on other vehicle options.
For the manual C60 versions, 84-89 are interchangeable, but differences in units exist between options for the rear window defogger (RPO C49) and the heated mirror option (RPO DL8). Differences in the face plates can be noted. This is easily seen in convertible cars as the rear defogger switch was not included due to a plastic rear window. (But the defrost switch can also be included, with minor changes in graphics, on convertible cars with the heated mirror option)
The Automatic C68 versions follow the same principle with options of 86-89 with RPO C49, without RPO C49, and 87-88 versions with RPO DL8 only. If one is not concerned about the operation of heated mirrors and window defogger since many cars are driven during the warmer months only, then it is not completely necessary to match these options in a replacement climate control.
Like instrument clusters, automatic climate control modules for the 86-89 cars can be very problematic. Before diving into an immediate replacement or rebuilt unit, it is best to discuss the issues you are experiencing with someone knowledgeable in these units since depending on problems experienced, the cause of the issue may not always lie in the dash mounted control module itself.
1984-1989 C60 Manual Climate Control (w/out rear defrost)
1984-1989 C68 Manual Climate Control (w/ rear defrost)
1986-1989 C68 Auto Climate Control
1986-1989 C68 Auto Climate Control (w/out rear defrost)
Dash Information Centers (84-89)
The dash information center, or commonly referred to as DIC, is the center dash switch panel located above the radio. It consists of a number of switches to change the displayed information on the instrument cluster. It also has a flat black panel area that contains a number of warning lights. While DIC’s for 84-89 cars all look visually identical, they are anything but the same.
There are two main versions of DIC’s for 84-89 cars and the change is related to the printed circuit board on the backside. These are 84-85 and 86-89 versions. When replacing a DIC it is necessary to stick to these two groups of year ranges. However, between the 86-89 DIC’s there are more changes relative to the black warning light overlay filter that had minor differences in printings for the various years. Those are 84-85 are the same, 86 is unique, 87-88 are the same and 89 is unique. The best thing to do if replacing a DIC for 86-89 years is to just swap out the black overlay filter from your existing DIC to the one that you are replacing rather than trying to purchase the exact one for your year.
A common failure of the 84-89 DIC’s is the separation of the two laminate layers of the printed circuit board on the rear. Once this starts, issues can arise within the printed circuit causing the DIC to not work correctly. Switches are also a common failure and can easily be replaced from another DIC of any 84-89 Corvette.
1984-1989 Dash Information Center
1984-1985 DIC Printed Circuit board
1986-1989 RH DIC Printed Circuit Board
1984-1985 DIC Cover Overlay
1989 DIC Cover overlay
Headlight and Fog Light Switch (84-89)
The headlight and fog light switches are the same among the 84-89 corvettes and can be used interchangeably without issue.
1984-1989 Headlight Switch
1984-1989 Fog Light Switch
Instrument Gauge Clusters (84-89)
While instrument clusters for 1984-1989 cars look the same when not illuminated, there are a number of differences. First off, instrument cluster of 84-89 cars are a common item that fails and needs attention. While there is a lot of information on the Internet for repairing the clusters, or many services to rebuild these, the purpose of this writing is only to identify differences among years. There were many different versions of gauge clusters for each year and just looking at all the different information in a GM parts guide is enough to make ones head spin. The important differences are visual changes in the gauge displays for different years and if the car had cruise control or not. The “brains” so to speak, of the cruise control are included in the gauge clusters of earlier cars. If you swap a cluster to your car from one that did not have cruise control, you will no longer have working cruise control.
The 84-89 clusters have a mechanical odometer. These odometers can be easily changed among clusters for keeping your existing mileage shown. However buyer beware, it also means that people can easily change an odometer to have a car show less miles that it really has.
1984 Instrument clusters are unique to 84 only. They have a different gauge appearance than those of other years. The 1985 instrument cluster is also unique to 85 only but has a gauge layout that looks verty similar to the 86-89 versions. Component wise the tach panel and the logic board from 85 versions are not interchangebale with 86 and later. Many 85 clusters needing repair were converted to 86 and up designs due to limitied part avaiability for the 85 version.
1984 Instrument Cluster
1985 Instrument Cluster Bezel
1986-1989 Instrument clusters can be used interchangeably but can be versions with and without cruise. The main displays of 1986 through 1989 are mostly the same. Differences appear with the 1986-1988 versions with the addition of an upshift arrow in the tach display with the words “Upshift for Best Fuel Economy” 1986-1988 also had an indication for overdrive above the numeric display for the tach. 1989 does not have the overdrive indication and the upshift arrow wording changed to just “One to Four” for the ZF6 transmission skip shift function.
1986-1988 Instrument Cluster
1989 Instrument Cluster Bezel
As stated above many different issues can be had with 84-89 versions from lights flickering, bulbs being burnt out, bad ambient light sensors that keep the display dim, and blurriness of the display. The blurry display is one of the more common issues that is caused by a bad polarized film on the face of an LCD. One way to easily spot bad polarized film is if you can see the speedometer and tachometer gauges with the car turned off like in the example photo. A cluster with good film should be completely black in both the left and right windows when not powered on.
Example of Bad Polarizing Film
1990-1996 Gauges and Dash Controls
Air Condition Climate Control Units (90-96)
The 1990-1996 A/C climate control modules follow the same color scheme differences carried out throughout the 90-96 cars. 1990-91 (gray with orange letters), 92-93 (black with orange letters) and 94-96 (black with white letters). Though again, there are more differences than just the colors.
Like the 84-89 versions options exist between automatic climate control (RPO C68) and manual climate control (RPO C60). Within the auto and manual versions are further differences depending on whether the car is a coupe, or a convertible and if the auxiliary hardtop was an option (RPO CC2) with the car originally. The basic difference of this comes down to the button for the rear window defogger. If the car is a coupe it has a normal image on the button for the rear defogger. If the car is a convertible without the auxiliary hardtop RPO CC2 option it will have a different image on the defogger button to indicate the button is for heated mirrors. If a convertible car had been purchased with the RPO CC2 hardtop option then the button would display the normal rear defogger symbol since this was available on the hardtops glass window. These variations are only present on the 90-91 (gray with orange letters) and the 92-93 (black with orange letters) units. By 1994 the convertible tops now had a glass rear window with a defogger built in. Therefor the 94-96 (black with white letters) only came in a manual C60 version and an automatic C68 version.
Like the earlier versions, automatic climate control modules for the 90-96 cars can be problematic. Before diving into an immediate replacement or rebuilt unit it is best to discuss the issues you are experiencing with someone knowledgeable in these units since depending on problems experienced, the cause of the issue may not always lie in the dash mounted control module itself.
1990-1991 C60 Manual Climate Control
1992-1993 C60 Manual Climate Control
1994-1996 C60 Manual Climate Control
1990-1991 C68 Auto Climate Control
1992-1993 C68 Auto Climate Control
1994-1996 C68 Auto Climate Control
1990-1991 C68 Auto Climate Control, Convertible w/out CC2 Hardtop Option
Dash Information Centers (90-96)
The 1990-1996 dash information centers follow the same color scheme differences carried out throughout the 90-96 cars. 1990-91 (gray with orange letters), 92-93 (black with orange letters) and 94-96 (black with white letters). When replacing you only need to match the colors.
The 90-96 DIC’s have the same style of printed circuit on the rear. Though these years seem less prone to separation of the two laminate layers as in the earlier cars. A common issue for these is the trip and fuel reset buttons to break off and become lost.
The 1990-1991 and the 1992-1993 have metal trim around the black display area. The 1994-1996 versions do not have this metal trim.
1990-1991 Dash Information Center
1992-1993 Dash Information Center
1994-1996 Dash Information Center
Headlight Switch Assembly (90-96)
The 1990-1996 headlight switch assemblies follow the same color scheme differences carried out throughout the 90-96 cars. 1990-91 (gray with orange letters), 92-93 (black with orange letters) and 94-96 (black with white letters). The 90-91 versions operated only the headlights and front fog lights. Starting in 1992 the switch assembly also included a button for the ASR traction control. When replacing units it is only necessary to match the original colors.
1990-1991 Headlight Switch
1992-1993 Headlight / ASR Switch
1994-1996 Headlight / ASR Switch
Instrument Clusters (90-96)
The instrument gauge clusters of the 1990-1996 cars are grouped into three main styles, 90-91 (gray with orange lettering), 92-93 (black with orange lettering) and 94-96 (black with white lettering). However within each year range there are options for ZR-1 or ’96 LT4 cars. These clusters can be identified by an 8k RPM tachometer rather than the 6k tachometers used on base models.
The 1990-1991 gauge clusters had a different layout display of the center LCD, while 92-96 all had the same LCD display layout.
The 90-96 clusters are much less problematic than the 84-89 versions, though they are not completely without their issues. Bad LCD’s leads the way as far as common issues. Again there are many repair services out there for these clusters, but good used replacements are easier to come across than the 84-89 versions since there were less issues with these.
Note* The vehicle mileage is NOT stored in the gauge cluster but rather the body control module on 90-96 cars. When swapping an instrument cluster it is as easy as plug and play, and your cars existing mileage will be displayed.
1990-1991 Instrument Cluster
1992-1993 Instrument Cluster
1994-1996 Instrument Cluster
1990-1991 ZR-1 8k Tach Cluster
1992-1993 ZR-1 8k Tach Cluster
1994-1996 ZR-1 & LT4 8k Tach Cluster
For further information on replacement items for your C4 corvette please feel free to give us a call or contact us with any questions.