* Damaged or Disconnected Wiring: The most likely culprit. The auto start system's installation often involves working near the vehicle's main wiring harness, which includes the wiring for the speedometer. A wire could have been:
* Accidentally cut or frayed: During the installation process.
* Dislodged from a connector: A loose connection is a common cause of intermittent or complete electrical failures.
* Damaged by a clamp or fastener: Improper routing of wires could lead to damage.
* Fuse Blown: While less likely to cause a complete failure, a fuse protecting the speedometer circuit might have blown during the installation process, possibly due to a short circuit caused by accidental wiring damage.
* Interference with Speed Sensor: The speedometer relies on a vehicle speed sensor (VSS). While less probable, the auto start installation might have inadvertently affected the sensor's wiring or its connection, leading to a faulty reading or no signal. This is more likely if the sensor is located in an area where the installer worked.
* Faulty Ground: A poor ground connection somewhere in the system (either related to the speedometer or the auto-start) could cause erratic behavior or failure.
Troubleshooting Steps:
1. Check Fuses: Inspect the fuses related to the instrument cluster and any fuses that might have been added or affected by the auto start installation.
2. Inspect Wiring: Carefully examine the wiring harness around the instrument cluster and the area where the auto start system was installed. Look for any damaged, loose, or disconnected wires. Pay special attention to any wires that were touched or moved during the installation.
3. Check the Vehicle Speed Sensor (VSS): Locate the VSS (its location varies by model year and engine) and check its connection. Sometimes, a simple cleaning of the connector can restore functionality. If possible, test the sensor itself with a multimeter.
4. Check Ground Connections: Ensure all ground points related to the speedometer and instrument cluster are clean and secure.
5. Review Auto Start Installation: If possible, consult the installation instructions for the auto start system to see if any wiring changes might have affected the speedometer circuit.
If you're not comfortable working with car wiring, it's best to take the vehicle to a qualified mechanic to diagnose and repair the issue. They have the tools and expertise to pinpoint the problem quickly and safely.
