Police vehicle upfit checklist: the parts list and what to decide first
Written by Shmaya Krinsky, K&K Emergency Systems, Opa-locka, Florida. We build and upfit ambulances, fire apparatus and police vehicles, and we sell the parts we install. Updated October 2026.
A patrol upfit is a list of decisions made in the right order. This is a checklist for a police vehicle upfit parts list, with what to decide for each item and where installs go wrong. This planning guide does not replace applicable law, your agency's specification or the vehicle manufacturer's requirements.
The short version
- Decide control and power first: the controller, siren and bar must work together, and the power distribution has to be sized from the exact equipment's installation data, within the vehicle maker's approved supply capacity.
- Parts fall into nine groups: roof or interior bar, grille and perimeter lights, siren and speaker, controller, push bumper, power distribution and protection, wiring and loom, mounting brackets, and cameras.
- Three installation problems to plan against are unsealed splices, undersized wiring, and wiring tapped into circuits without a plan.
- Safety note: some of these items change how the vehicle behaves, including airbag deployment, starting and crash performance. Do not tap or modify airbag/SRS wiring or sensors, or connect equipment directly to the vehicle's CAN bus wiring. For starting, ignition or vehicle-data functions, use only the exact vehicle maker's designated upfitter connections and approved interfaces. Use the vehicle maker's designated upfitter power and signal points, and read the vehicle manufacturer's modifier guide before you drill, mount or tap anything.
The parts, and what to decide for each
| Item | Decide | Watch for |
|---|---|---|
| Roof or interior light bar | Size, colors, class per color, serial or hardwired control | A bar that does not match the controller. See how to choose a light bar. |
| Grille, bumper and perimeter lights | Locations, colors, flash patterns, ingress rating for the location | Low mounting spots that see spray. See IP ratings explained. |
| Siren amplifier and speaker | Where the speaker faces and what it must clear | Siren wiring and speaker placement near airbag sensors or deployment paths. |
| Controller | Which functions it runs and from where the officer reaches it | A controller that cannot drive the bar or siren you chose. |
| Push bumper | Whether the vehicle maker publishes guidance for your model | Effect on airbag deployment and crash performance; obstruction of sensor, radar or camera fields of view; and restricted cooling airflow. |
| Power distribution and circuit protection | Worst-case simultaneous load, the vehicle maker's approved power source, fuse or breaker rating per circuit | Feeder fusing far from the battery; a branch fuse sized above its branch; one circuit feeding too much. |
| Wiring and loom | Routing, gauge, connectors, sealing | Unsealed splices and wire thinner than the original. |
| Mounting brackets | Vehicle-specific fitment, and what the surface can carry | Drilled holes left unsealed or unprotected. |
| Camera system | Coverage, connector rating, where it stores or sends video | Water in the connector. |
Plan power before you buy
Plan the worst-case simultaneous loads using the exact equipment's installation data, then size each circuit's wiring and protection for its load, run length, voltage drop and component limits, within the vehicle manufacturer's approved supply capacity. Amperage depends on the exact model, enabled functions and duty cycle; obtain its operating and maximum-load specifications. Federal Signal's Allegiant light bar manual describes a light system as a high-current system, calls for separate positive and negative connections, and says a suitable fuse belongs on the positive battery connection as close to the battery as possible, with wires and fuses rated for the system amperage. That is one product's instruction, not permission to connect anywhere on the vehicle.
For sirens, follow the exact siren's wiring instructions and the vehicle manufacturer's approved power provisions; size protection for the circuit and conductors being protected, and keep power leads as short and direct as specified. Branch fuses are sized for the branch and the device manual, not for the whole vehicle load.
Document the vehicle's power layout, OEM-approved power and ground connections, separately protected circuits, labels and spare-capacity allowance. Confirm the vehicle's charging capacity, battery capacity, starting reserve and load-management requirements; use only its approved low-voltage equipment supply, and do not connect to a hybrid high-voltage battery. Where the vehicle maker provides an upfitter connector or power distribution center, check its published limits in the modifier guide. See our auto ejects, inverters and chargers for charging and shoreline gear.
Common mistakes
Unsealed splices. Federal Signal's siren manual says splice joints should be soldered or crimped with butt connectors and properly insulated, and that splices exposed to the elements should be adequately sealed and insulated. That does not authorize splicing a circuit the vehicle maker prohibits. Seal and insulate any splice exposed to the elements.
Undersized wiring. The same manual says extended wires should not be a lesser gauge than their originals.
Tapping circuits without a plan. Do not tap or modify airbag/SRS wiring or sensors, or connect equipment directly to the vehicle's CAN bus wiring. For starting, ignition or vehicle-data functions, use only the exact vehicle maker's designated upfitter connections and approved interfaces. Use the vehicle maker's designated upfitter power and signal points, and follow the exact vehicle's diagrams and procedures; a documented reason does not authorize a prohibited connection. Federal Signal's light bar and siren manuals both warn against installing aftermarket equipment that connects to the vehicle wiring without reviewing the vehicle manufacturer's wiring diagram, and say to ensure the installation does not affect vehicle operation or mandated safety functions. This affects how the vehicle starts, locks and protects its occupants.
Mounting in airbag paths. Federal Signal's instructions say not to install equipment or route wiring in the deployment path of an airbag, and Ford states that push bars could adversely affect air bag deployment in frontal impacts and that it does not test aftermarket equipment with its components. Follow the modifier guide for your vehicle and year.
Drilled holes. Federal Signal's Allegiant manual says to check both sides before drilling, deburr holes, protect passing wires with grommets or suitable loom, and seal exterior holes with Motorcraft T-A-2-B or equivalent; follow the vehicle and mounting-kit instructions for the attachment location, supporting structure, specified hardware and tightening torque.
Frequently asked questions
What is in a typical patrol upfit? The table above lists the groups to plan. Your agency's specification, applicable law and the vehicle maker's requirements decide which you need.
Can I mix brands? Federal Signal's manual warns that combining light heads and a power supply from different manufacturers may reduce warning effectiveness and damage components. Stay within one maker's system unless the maker documents the pairing.
Where can I find the vehicle manufacturer's guidance? Ford publishes Police Modifier Guides for its Police Interceptor models (see Ford upfit publications), and its Body Builder Advisory Service covers commercial upfitters. Other makers publish their own. Select the manufacturer's modifier guide and wiring diagrams for the vehicle's exact model year, model and powertrain before installation.
Do I need a camera? Confirm your agency's camera requirements and any applicable legal or contractual requirements. If you add one, check the connector's ingress rating as well as the camera body.
Who does the install? Call us at (305) 317-2619 and we will talk through the layout.
Browse our light bars, emergency lighting, sirens and speakers, perimeter lighting, scene and compartment lighting and camera systems.
About this article: it was drafted with AI assistance and fact-checked against the standards bodies and manufacturer publications cited in the text. AI-written content can contain errors and standards change, so facts here may be wrong. Where we describe our own practice, it is our practice, not a requirement of any standard. Confirm any requirement with the standard, the manufacturer, or with us before you buy or install.