The completely redesigned Mustang was available in a 4.0 V6 or the 4.6 V8 model, and both hardtop and convertible options. Many owners reported having sticky gauges, needles that have stopped working altogether, or speedometers that act strangely.
The root cause of strange, sometimes dangerous, gauge behavior is found deep within the instrument cluster. You can also search online for Mustang barometer clusters.
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A small electric motor is behind each gauge. This marvel of modern engineering is truly a marvel. It receives a signal via a circuit board microprocessor. The motor responds by moving the gauge needle in the correct position.
There are two options available for frustrated Mustang owners. You can take your Mustang to the dealer to have the cluster replaced. However, there is no recall so you will be responsible for the $500-$700 bill. You can also replace the part by buying a secondhand, but it will likely have the same motor problems and fail over time. Also, the mileage reading will need to be programmed to match your vehicle's.
A speedometer specialist with experience in working on Mustangs can repair your cluster. Before you hire a specialist to repair your cluster, do your research. Ask about the warranty, turn-around time, shipping costs, and shipping time. These things can vary widely between specialists. You can even search online for more information about the Mustang gauge cluster.