Need a reliable relay to boost an auxiliary heater’s performance? Three strong options cover common HVAC and vehicle setups: a compact 12 V sealed ACDelco Gold relay for tight, moisture-prone spaces; a rugged APFR-380 24 VAC fan relay built to handle high inrush currents; and a DIN‑mount ACDelco Gold D1724C with silver contacts designed for frequent cycling.
Each pick balances coil voltage, contact rating, and mounting style so selecting the right relay fits your heater’s electrical and space constraints.
Practical choices help extend component life and improve heater responsiveness.
| ACDelco Gold Auxiliary HVAC Blower Motor Relay |
| Professional Grade | Intended Application: HVAC auxiliary blower motor control | Contact Type / Pole: Normally Open | Mounting / Connector Style: Press-in (through hole) mount | VIEW LATEST PRICE | Read Our Analysis |
| APFR-380 24V AC Heavy-Duty Fan Relay (SPST) |
| Heavy-Duty Choice | Intended Application: HVAC fans/blowers, furnaces, pumps, general appliance/fan control | Contact Type / Pole: SPST (single pole, normally open switch) | Mounting / Connector Style: Panel/terminal mount with six wire hook-up terminals | VIEW LATEST PRICE | Read Our Analysis |
| ACDelco Gold D1724C (89057568) Multi-Purpose Relay |
| Versatile Pick | Intended Application: HVAC auxiliary/heater control (multi-purpose relay) | Contact Type / Pole: Normally Open | Mounting / Connector Style: DIN rail mount with screw terminals | VIEW LATEST PRICE | Read Our Analysis |
More Details on Our Top Picks
ACDelco Gold Auxiliary HVAC Blower Motor Relay
Provided you want a reliable replacement that fits like the original and keeps your auxiliary heater and air conditioning running smoothly, the ACDelco Gold 15-50961 blower motor relay is a smart choice. You’ll like its 12 volt coil and three terminal through hole design that snaps into place with press in mounting. It’s made to match OEM form and function, so it swaps in without fuss and keeps fans working automatically. IP67 and UL listings give you confidence in wet and rough conditions. At about 1.41 ounces and compact size it’s easy to handle, install, and trust.
- Intended Application:HVAC auxiliary blower motor control
- Contact Type / Pole:Normally Open
- Mounting / Connector Style:Press-in (through hole) mount
- Rated for AC or DC Control Circuits:12 V DC coil/control
- Aftermarket / Professional Grade:ACDelco Gold professional/premium aftermarket
- Application Focus on Motors / Blowers:Specifically for blower motor (auxiliary HVAC blower)
- Additional Feature:IP67 rated sealing
- Additional Feature:12V DC coil
- Additional Feature:Press-in mounting
APFR-380 24V AC Heavy-Duty Fan Relay (SPST)
Should you need a rugged relay that handles heavy-duty fan and motor loads without fuss, the APFR-380 24V AC Heavy-Duty Fan Relay is a great choice for HVAC technicians, maintenance crews, and handy homeowners. You get a PR380A model with a 24 VAC coil at 50/60 Hz and a single pole SPST isolated AC switch. It manages heavy starts with up to 60 A LRA at 125 VAC and carries 18 A at 277 VAC resistive. Install quickly using six wire terminals and the printed wiring diagram. It suits blowers, furnaces, humidifiers, pumps, and heat sequencers.
- Intended Application:HVAC fans/blowers, furnaces, pumps, general appliance/fan control
- Contact Type / Pole:SPST (single pole, normally open switch)
- Mounting / Connector Style:Panel/terminal mount with six wire hook-up terminals
- Rated for AC or DC Control Circuits:24 VAC coil/control (50/60 Hz)
- Aftermarket / Professional Grade:Heavy-duty aftermarket HVAC relay (commercial-grade spec)
- Application Focus on Motors / Blowers:Rated for motor loads (FLA/LRA ratings for blowers and motors)
- Additional Feature:24 VAC coil
- Additional Feature:High locked-rotor rating
- Additional Feature:Six-terminal wiring
ACDelco Gold D1724C (89057568) Multi-Purpose Relay
Should you need a dependable replacement relay that’s built for HVAC and auxiliary heater use, the ACDelco Gold D1724C will suit you well because it balances durability with a straightforward design you can trust. You’ll appreciate its compact 2.8 across 2.5 across 2.6 inch body and light 3.68 ounce weight during installing in tight spaces. It mounts on DIN rails and uses screw terminals with three connections, so you can wire it without guesswork. With silver normally open contacts rated 17 amps and 19.6 watts, it handles common loads reliably. The aftermarket fit and ACDelco support give you extra confidence.
- Intended Application:HVAC auxiliary/heater control (multi-purpose relay)
- Contact Type / Pole:Normally Open
- Mounting / Connector Style:DIN rail mount with screw terminals
- Rated for AC or DC Control Circuits:(Designed for vehicle/HVAC electrical systems — coil/control used in automotive/HVAC applications; compatible with typical HVAC control voltages)
- Aftermarket / Professional Grade:ACDelco Gold professional/premium aftermarket
- Application Focus on Motors / Blowers:Multi-purpose relay intended for HVAC systems including heater/blower control
- Additional Feature:DIN-rail mountable
- Additional Feature:17 Amp contact rating
- Additional Feature:Silver contact material
Factors to Consider When Choosing Auxiliary Heater AC Control Relays
Upon selecting an auxiliary heater AC control relay, begin with matching coil voltage and checking the relay’s current and load rating so it won’t overheat or fail. Also look at contact configuration and mounting and connector style because they determine how the relay fits and works in your system. Don’t forget environmental protection ratings so the relay can handle moisture, dust, and temperature changes without surprises.
Coil Voltage Compatibility
Because the relay coil has to match the control circuit, picking the right coil voltage is one of the most critical decisions you’ll make for an auxiliary heater AC control relay. You should initially confirm the nominal voltage such as 12 V DC, 24 VAC, or 120 VAC so the relay will activate and not get damaged. Next, check whether your system uses AC or DC, since AC coils need the correct frequency, usually 50 or 60 Hz, while DC coils do not. Also look at the coil operating range and minimum pull in voltage so it works with real world voltage drops. Finally, review coil power draw, inrush behavior, and suppression or higher tolerance for long runs or noisy environments.
Current And Load Rating
Pick a relay that can handle more than your heater or blower motor draws, and you’ll save yourself from smoke, downtime, and costly replacements. You should size the relay’s continuous current rating at least 25 to 50 percent above the motor’s running current so it won’t overheat or wear contacts fast. Also check the locked-rotor or inrush rating, because startup current can be five to ten times higher and can weld contacts unless the relay can’t cope. Match contact voltage and type to the circuit so the relay suits your AC mains, phase, and load type, whether resistive or inductive. Look at short-term duty, thermal dissipation, and duty cycle for frequent switching. Pick durable contact materials like silver alloys for heavy use.
Contact Configuration Type
As you plan the wiring for an auxiliary heater, the relay’s contact configuration becomes one of the initial decisions that will shape safety, control, and reliability. You’ll choose NO, NC, or changeover contacts depending upon the heater circuit must close only whenever active, stay closed whenever de-energized, or switch between outputs. Match poles to your wiring: single-pole for one conductor, double-pole to break both supply and neutral or to switch two circuits. Also confirm SPST, SPDT, or DPDT arrangements match your control logic and safety interlocks, like combining thermostat signals or fan controls. Check contact materials and ratings for resistive and motor loads. Finally, consider auxiliary contacts or timing for stage sequencing and feedback to control modules.
Environmental Protection Rating
Upon selecting a relay for an auxiliary heater, environmental protection rating matters just as much as electrical specs, and it’s what keeps your system reliable in real conditions. You should pick an IP rating that fits the location. For wet or exposed HVAC compartments, IP67 keeps dust and water out. In the presence of salt spray or chemicals, look for sealed enclosures or conformal-coated internals to stop corrosion from ruining contacts. Also check temperature ratings and thermal derating so the relay won’t fail in hot engine bays or tight cabinets. Vibration and shock specs matter whenever you’re near fans, compressors, or on vehicles to prevent contact bounce. Finally choose enclosures and gaskets that resist UV and ozone for long outdoor life.
Mounting And Connector Style
Whenever you’re fitting an auxiliary heater relay, the way it mounts and plugs in matters as much as its electrical ratings, and getting this right makes installation and future service much easier. You should pick a mounting style—press‑in, DIN‑rail, panel mount, or PCB—that fits your space and holds the relay securely. Then match connector types like screw terminal, spade tab, wire pigtail, or PCB pins to your wiring harness to avoid splices. Check terminal count and layout so coil, common, NO, and NC circuits fit without rewiring. Consider serviceability and choose removable or plug‑in mounts should you expect frequent swaps, or fixed mounts for long runs. Finally, confirm materials and sealing resist vibration, moisture, and corrosion for reliable long‑term connections.
Thermal And Inrush Handling
You picked the right mounting and connector style, and now you’ll want to make sure the relay can handle the heat and the big current spikes that come with blower and heater motors. Check motor-rated inrush LRA and full-load FLA numbers and match them to the motor’s stall and running currents so contacts don’t weld or fail. Look at contact material and amp capacity, like silver alloy contacts sized for repeated arcing and thermal stress. Confirm enclosure thermal rating and ambient temperature range so the relay won’t overheat or derate in hot locations. Match coil voltage, power draw, and duty cycle to frequent starts and temperature swings. For heavy inrush, choose parts with built-in suppression or add external snubbers or pre-charge options.
Certification And Standards Compliance
Because safety and reliability matter whenever you’re picking an auxiliary heater relay, you should check certifications and standards initially and promptly. You want relays certified to UL, cUL, CE, or IEC so you know insulation, dielectric strength, and operation were tested for the voltages and temperatures you’ll face. Also verify IP ratings like IP67 whenever dust or moisture are present so sealing matches the environment. Check contact voltage and current ratings against steady state and inrush LRA needs and confirm the certification covers those loads. Look for compliance with NEC or local electrical codes and any HVAC specific certifications that affect installation and insurance. Finally, confirm manufacturer tests for temperature range, vibration, and shock so the relay will survive your conditions.
