A speedometer is one of the more important parts of your car—a safety feature that protects you both from unsafe driving and from the financial repercussions of getting a speeding ticket. You can spend several hundred dollars for a mechanic to install a new device, or you can take a weekend to do the work yourself. This is a relatively complex car repair, and you should not attempt it as your first automotive project.
Preparing Prior to Installation
Read your vehicle’s owner’s manual. Before you touch so much as a screw around the vehicle’s instrument cluster, thoroughly read the owner’s manual. You will find helpful information in the manual concerning the wiring around the dash cluster, as well as a schematic for the instrument panel that will help locating the correct hardware, wiring, components, etc.
Many cars, especially those purchased used from private owners may no longer have the owner’s manual. You might be able to find a downloadable version of the manual online from the manufacturer’s website, but if not, you should be able to order one directly from the manufacturer via a certified dealership.
Find an appropriate speedometer. The dimensions of a speedometer vary from vehicle to vehicle and after-market products are most certainly not universal. You can consult the parts department at a certified dealer to ensure that you order a speedometer that will fit properly into your instrument panel.
The gauge won’t just need to meet dimension specifications, but you also have to consider what all connects to your specific vehicle’s speedometer. Some have one wire for a dash light while some have two. Vehicles with an automatic transmission may also have a gear selection wire connected to the speedometer. Ordering a component with everything you need is essential.
If you would rather not go through a dealership but you have a trusted mechanic, he or she will likely have access to the same parts information and can also ensure that you order an appropriate speedometer.
Gather the necessary tools. While removing and installing a speedometer doesn’t require any specialized equipment, you do need to make sure that you have both phillips and flathead screwdrivers on hand, as well as a pair of pliers, a good wrench set, and possibly a good socket wrench set.
Disconnecting the Current Speedometer
Disconnect your vehicle’s battery. The wiring to your current speedometer feeds from the vehicle’s battery, and you risk shocking yourself while dealing with these wires if you do not disconnect the battery first thing.
Loosen the screws around your vehicle’s instrument cluster. One of the schematic pages in your owner’s manual should point out the location of each screw you will need to remove. Pay close attention to which screws instead of removing every screw around the cluster since some of them may not need to be removed.
Make sure you store the screws in a safe spot where you will not lose them while working on the installation.
After removing the screws, the face plate around the instrument panel will still be held in place by pressure clips. Use a flathead screwdriver to pry an edge of the plate forward gently and pull lightly on the plate until all of the pressure clips release. Be very careful during this because it is possible to break the clips.There will be large electrical plugs connected to buttons such as your hazard lights as well. You can hold the release to easily remove these plugs. In most model vehicles, these plugs only fit into their proper housing, so incorrectly connecting them later is impossible. When in doubt, label each with a piece of tape as you disconnect it.
Pull the instrument cluster out of the dash. Though all of the wiring will still be connected, you will have some room to ease the instrument cluster forward from the dash.
Locate your speedometer in the instrument cluster. The backside of your speedometer will be a rounded or squared box with several wires attached for powering the gauge itself as well as the dash lighting that illuminates the gauge when you turn on your headlights.
Take pictures of the current configuration. When all else fails, connecting the wiring to look like the picture is better than trying to remember how the configuration looked before disconnecting the old speedometer.
Between the pictures you take and the schematic in your owner’s manual, you should feel more comfortable disconnecting the old speedometer as well.
Disconnect the wiring from the current speedometer. Depending on your vehicle’s manufacturer, disconnecting any wiring connectors may require the use of pliers, wrenches, and/or a screwdriver. Loosen any screws or connectors until the wiring comes off easily. Don’t force it. Otherwise, you may turn the relatively easy gauge swap into a much more difficult electrical problem that requires a professional.
There will likely be additional screws on the back of the instrument panel that hold the speedometer in place. You will also need to remove these screws in addition to the wiring to completely free the gauge from the panel.
In some model vehicles, this wiring may all be joined into one single plug that is snapped into place in the back of the speedometer. For this setup, simply push down on the release on the plug and remove it from the speedometer.
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Installing the New Speedometer
Set the new speedometer in place on the instrument panel. Reattach it by screwing it to the mounting points that held the old speedometer in position.
Reconnect lighting connections for the speedometer. Reconnect the wiring as your owner’s manual schematic and your reference pictures indicate. You may have to tighten down some connections as well. If the model is compatible with your car, they should connect as the old one did.
If your model vehicle has a joint-wiring plug and you ordered a suitable speedometer, then the plug should snap easily into place.
Slide the instrument cluster back into position. You will have to replace any screws that you initially removed from the cluster as well.
Replace the panel face plate in front of your instrument panel. You will have to reconnect any electrical plugs that you disconnected when removing the plate as well as snap the pressure clips back in place before tightening the screws in place.
Don’t tighten the screws down too hard since this piece is plastic in most vehicles and can break.
Reconnect your car’s battery. After you reconnect it, confirm that the electrics turn on. Since you likely had to unplug a few items connected to the panel plate, check everything in the dash from your hazard lights to your turn signals and headlights. Make sure everything is in working order.
Check the speedometer’s calibration. By using a stopwatch and your odometer, you can test drive your car and confirm that the new speedometer is accurate.
Pick a large empty parking lot or another area where you can maintain a slow consistent speed. If you go one mile (odometer) in three minutes (stopwatch) at a consistent speed, then you know you were traveling at 20mph.
If your new speedometer is off, follow the manufacturer’s directions that came with your specific speedometer to calibrate it.