Simple Issues (often easily checked):
* Blown Fuse: Check the fuse box for a blown fuse related to the instrument cluster or speedometer. This is the easiest and cheapest thing to check first.
* Loose or Corroded Connections: The speedometer cable (if it's cable-driven, less likely in a '92 Dynasty which likely uses a Vehicle Speed Sensor (VSS)) or the electrical connectors to the instrument cluster might be loose or corroded. Inspect and clean these connections.
* Faulty Speedometer Cable (if applicable): If it *is* cable-driven, the cable itself might be broken, frayed, or disconnected. This would require inspection and likely replacement. Less likely in a '92 Dynasty though.
* Instrument Cluster Failure: A problem within the instrument cluster itself, such as a failed speedometer motor or a faulty circuit board, could be the culprit. This often involves replacing the entire instrument cluster.
More Complex Issues:
* Vehicle Speed Sensor (VSS) Failure: This is the most likely culprit in a 1992 vehicle. The VSS is a sensor that measures the speed of the vehicle and sends that information to the instrument cluster. A faulty sensor will prevent the speedometer from working, and often other speed-related functions like cruise control as well.
* Wiring Problems: A break or short in the wiring between the VSS and the instrument cluster could interrupt the signal. This requires tracing the wiring harness.
* PCM (Powertrain Control Module) Issue: In some cases, a malfunctioning PCM can affect the speedometer's operation. This is less common but possible.
* Gearbox Problems: While less frequent, issues within the transmission could also affect the VSS signal, although other symptoms would likely be present (e.g., shifting problems).
Troubleshooting Steps:
1. Check the fuses.
2. Inspect the VSS connector and wiring for damage or corrosion. (This is the most likely cause in a '92)
3. If cable-driven, inspect the speedometer cable. (Less likely, but possible)
4. Have the VSS tested. An auto parts store may be able to test it for you.
5. Consult a repair manual: A repair manual specific to your 1992 Dodge Dynasty will provide detailed diagrams and troubleshooting steps.
If you're not comfortable working on your car yourself, take it to a qualified mechanic for diagnosis and repair. They'll have the tools and expertise to pinpoint the exact problem efficiently.
