Common signs of a bad pressure switch include the compressor not turning on or off at the correct pressures, rapid on/off cycling, or no response at all. You can test the switch with a multimeter to check continuity across the terminals when the system reaches trigger PSI. If the contacts don’t open or close properly, or the switch fails to engage at the right pressure range, it likely needs replacement.

No—pressure switches and flow switches serve different purposes. A pressure switch activates based on air or fluid pressure levels inside a system, while a flow switch detects the movement of fluid through a pipe. HornBlasters air systems use pressure switches to manage compressor function. Flow switches are more common in HVAC or water-based systems where fluid movement, not pressure, needs to be monitored.

The correct PSI pressure switch depends on your air system’s compressor, tank size, and overall application. Common options include 85/105 PSI, 110/150 PSI, and 165/200 PSI. For train horn kits, 110/150 PSI switches are the most commonly used, offering fast fill times with reliable volume. For air suspension systems, 165/200 PSI switches are preferred to ensure adequate pressure for lifting and maintaining ride height. Always match your pressure switch to the compressor’s rated cutoff and your system’s operating range.

A sealed pressure switch has a weather-resistant cover that protects internal contacts from moisture and debris—ideal for off-road, marine, or under-vehicle installations. Unsealed switches are better suited for clean, dry environments. If your air system is exposed to the elements, a sealed switch offers longer-lasting reliability.

Some pressure switches come with an internal relay, while others require an external one. A relay helps handle the compressor’s current load without overloading the switch. For high-draw compressors, using a pressure switch with a relay (or wiring one in) is strongly recommended to avoid switch failure or overheating.