How are Instrument Clusters diagnosed?
Most late model vehicles are programmed to put the instrument cluster through a series of self-checks upon engine startup. A technician who observes this process by watching the display while the key is initially turned on will be able to take note of any features that are not operating or lighting up during the vehicle self-check. All of the lights should come on momentarily. The technician will look for any dark spots that fail to light up. On some models, this self-test can be manually initiated and it will produce an error code that can be interpreted by the technician. A technician can also check the voltage supplied to the instrument cluster and compare it to the values displayed on a wiring diagram. In some cases, especially if only one feature of the instrument cluster is inoperative or erratic, the cause may be not the cluster itself, but the sending unit that delivers the signal to the cluster. A technician can test the sending unit, or (in some instances) ground the sending unit to produce a measureable effect in the cluster. A blown fuse is not usually a cause of instrument cluster malfunction, but rather a symptom of a related electrical issue, such as a short circuit.
How is an Instrument Cluster replaced?
The procedure for replacement of the instrument cluster varies widely from one vehicle to another. The concept is the same. Access to the instrument cluster is not. It is important to obtain the vehicle-specific repair procedure to access and remove the cluster. A technician will disconnect the battery whenever the electrical system is being serviced and follow the procedure to remove any trim panels or accessories that are in the way of the instrument cluster. Once the cluster is loosened from its location and its wiring harness plugs disconnected, it is carefully pulled from its position in the dashboard. Tampering with the odometer is illegal, so the instrument cluster is protected to prevent abuse. The technician needs to remove the odometer chip from the old cluster and insert it into the new one to transfer the odometer reading. (Otherwise, the new cluster needs to be programmed and certified). The cluster is connected and reinstalled, followed by replacement of any trim or accessories that were removed.