Mars Relays

Mars Relays: Dependable Electrical Control for HVAC/R Systems

Mars has been a cornerstone of the HVAC/R components industry since 1946, and its lineup of relays reflects decades of engineering focus on durability, broad compatibility, and straightforward field replacement. Whether a technician is restoring a residential air conditioner or servicing a commercial refrigeration unit, Mars relays are designed to step in with confidence.

A Relay for Every HVAC/R Application

Mars organizes its relay offerings into several distinct product families, each engineered for specific switching demands within heating, cooling, and refrigeration systems:

• Potential Relays (One-On-One Direct Replacement Series): These are engineered as exact replacements for original equipment manufacturer parts, emphasizing long-term reliability and straightforward swaps. They carry UL/CSA listings and are A2L refrigerant compliant, keeping technicians aligned with modern refrigerant standards.
• Series 903 General Purpose Switching Relays: The Series 903 is among the most widely used relay families in air conditioning today. Available in 24V, 110/120V, and 208/240V coil voltages, these 2-pole relays cover air conditioning, refrigeration, heating, fan controls, and general-purpose appliance switching. They are cross-referenced to replace Honeywell and White-Rodgers/RBM units, with molded terminal numbers and wiring diagrams printed directly on the relay body for fast, accurate installation.
• Heavy Duty Fan Relays: Designed to handle heavier switching loads in a compact form factor, Mars Heavy Duty Fan Relays include a universal mounting bracket, 0.25-inch quick-connect terminals, and cross-reference packaging — built to replace WR/Essex/RBM Type 184 units.
• Power Relays (Series 903): Covering SPST, SPDT, SPNO-SPNC, and DPDT contact configurations across a range of pick-up and drop-out voltages, these relays serve demanding load-switching applications in HVAC control panels and equipment.

Why Mars Relays Stand Out

What sets Mars relay products apart is the brand's deep commitment to universal replaceability and field-serviceable design. Wiring diagrams and terminal designations are molded or printed directly onto each relay, reducing installation errors. Packaging consistently includes instructions and cross-reference guides, so technicians can verify fitment on the spot. Across the relay lineup, UL and CSA listings provide third-party assurance of electrical safety compliance.

Mars relays also carry a contact rating of 35A at 400 VAC on potential relay models and 18A ratings across much of the Series 903 power relay range — specifications that hold up under the demanding duty cycles of air conditioning compressors and fan motors.

Backed by U.S.-based manufacturing and now part of the RectorSeal family, Mars continues to be a go-to source for HVAC professionals who need reliable electrical components fast. Browse the full selection of relays or explore the complete Mars brand catalog to find the right component for your system.