Before starting this test, make sure the battery is charged, that all fuses are good, and that the cluster is connected to the wiring harness connector.
1) Turn the key on (engine off).
What should happen at this point is the four illumination bulbs should light up full brightness, and all segments on the cluster should turn on. After the first two seconds, the display should resolve into 0MPH/0RPM. After that, the cluster starts responding to light from the photocell. If the cluster is somewhere dark, the brightness may decrease. If you're out in sunlit conditions, it should remain full brightness. If not, there may be a problem with the photocell.
Here's a link to a diagram of the wiring to the 84-89 Instrument Panel:
2) Measure DC voltage between pin D5 and the negative terminal of the battery (not some other ground). It should be battery voltage. If not, recheck the LCD fuse - it may be loose or blown.
3) Measure DC voltage between pin C16 and the negative terminal of the battery. It should be battery voltage. If not, check the CLSTR fuse - it may be loose or blown.
4) Measure DC voltage between pin D16 and the negative terminal of the battery. It should be battery voltage. If not, check the CLSTR fuse - it may be loose or blown.
5) Measure DC voltage between pin D1 and the negative terminal of the battery. It should be 0.00V, or some very low voltage. If not, clean ground G201 and repeat this test.
6) Measure DC voltage between pin D3 and the negative terminal of the battery. It should be 0.00V, or some very low voltage. If not, clean ground G104 and repeat this test.
If the wiring checks out OK, the cluster should light up and at least show 0MPH/0RPM. If not, there is likely a problem inside the cluster. If so, let's do a bit more checking:
7) Turn the key on (engine off). Note what happens during the first two seconds after the key is turned on.
8) Look carefully at the displays. If different random segments turn on each time the key is turned from off to on, AND the illumination bulbs are off, the likely issue is that the power supply is bad. The screen won't light up, but some of the segments will change at random. https://batee.com/collections/84-89-corvette-parts/products/new-royal-premium-power-supply-1984-88
9) If the illumination bulbs light up, but you still can't see info on the LCD panels, have a look at the polarizing film page to see if yours looks like it may be faded. https://batee.com/collections/84-89-corvette-parts/products/lcd-panel-restoration-kit
10) If the illumination bulbs remain dark, but you can see correct info showing on the LCDs, the likely issue is that the backlight connector has failed and needs to be replaced. https://batee.com/collections/84-89-corvette-parts/products/84-89-backlighting-board-connector-repair-kit
11) If the illumination bulbs remain dark AND you see no correct information OR random segments turning on, the likely cause is that the power supply shorted, and that caused the 12 pin backlight connector to fail. https://batee.com/collections/84-89-corvette-parts/products/new-royal-premium-power-supply-1984-88 and https://batee.com/collections/84-89-corvette-parts/products/84-89-backlighting-board-connector-repair-kit
12) If it lights up, shows 0MPH, 0RPM, and shows incorrect battery voltage, the power supply is likely outputting the wrong voltage and needs to be replaced. https://batee.com/collections/84-89-corvette-parts/products/new-royal-premium-power-supply-1984-88
We hope this helps you to diagnose your 84-89 Cluster. If not, call or email BATEE service and we'll help any way we can!
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- Tags: 1984, 1985, 1986, 1987, 1988, 1989, Cluster, Dash, Gauge, Instrument Panel, IP, Light