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Best Auxiliary Heater & AC Control Relays of 2026

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Robert Reyes

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Auxiliary Heater & AC Control Relays are essential components in vehicles that provide heating and cooling systems. These relays are responsible for controlling the flow of electricity to the auxiliary heater and AC systems, ensuring they operate efficiently and effectively. The auxiliary heater relay is responsible for controlling the heater's operation, while the AC control relay is responsible for regulating the AC system's functions. These relays are designed to withstand high temperatures and heavy usage, making them durable and reliable. They are compatible with a wide range of vehicles and are easy to install. Overall, Auxiliary Heater & AC Control Relays are crucial for ensuring comfortable driving experiences in all weather conditions.

At a Glance: Our Top Picks

Top 10 Auxiliary Heater & AC Control Relays

#TOP 1

Dorman 904-300 Intake Heater Relay

Dorman 904-300 Intake Heater Relay Cover

Dorman 904-300 Intake Heater Relay Compatible with Select Dodge / Ram Models

The Dorman 904-300 Intake Heater Relay is a durable and trustworthy replacement part that is designed to match the fit and function of the original relay for select Dodge/Ram models. This relay is made from quality components to ensure reliable performance and a long service life, making it the ideal solution for damaged or failed original parts due to fatigue. To ensure the perfect fit, input your vehicle's make, model, and trim level into the garage tool.

9.9
FTB Score

What We Like

  • Durable and long-lasting
  • Reliable performance as an ideal replacement for damaged or failed parts
  • Designed to match the fit and function of the original relay on select Dodge/Ram models
#TOP 2

X AUTOHAUX 75mm Car Auto Heater Ducting Vent Outlet

X AUTOHAUX 75mm Car Auto Heater Ducting Vent Outlet Cover

X AUTOHAUX 75mm Car Auto Heater Ducting Warm Air Vent Outlet 360 Degrees Rotatable Black

This Car Auto Heater Ducting Warm Air Vent Outlet is made of durable plastic material, and is compatible with 75mm Warm Air Vent Outlets. It can prevent your car surface from scratches and dust, and is a great replacement for your old or broken one.

9.8
FTB Score

What We Like

  • Durable plastic material
  • Compatible with 75mm Warm Air Vent Outlets
  • Prevents car surface from scratches and dust
  • Easy replacement for old or broken vent outlets
#TOP 3

Xximuim 360° Rotatable Warm Air Vent Outlet (75mm)

Xximuim 360° Rotatable Warm Air Vent Outlet (75mm) Cover

2pcs 360 Degrees Rotatable Warm Air Vent Outlet Car Heater Duct Hose Pipe Warm Air Vent Outlet for Parking Heater Air Conditioner Steering Car Bus Boat Eberspacher, Webasto, Propex Heaters (75mm)

The Xximuim Rotatable Air Vent is designed with durable plastic that resists wear, corrosion, and deformation, ensuring long-lasting use. Its 360-degree rotation feature lets you easily direct warm air exactly where you want it, providing comfort tailored to your needs. This vent also protects your car’s air outlet from scratches and dust, keeping it clean and in good condition. Installation is hassle-free, requiring no drilling or special tools, so you can set it up quickly and start enjoying better air flow without any modifications.

9.6
FTB Score

What We Like

  • Durable plastic construction
  • 360-degree adjustability
  • Protects vent surface
  • Easy installation
#TOP 4

Dorman Intake Heater Relay for Dodge Models

Dorman Intake Heater Relay for Dodge Models Cover

Dorman 904-356 Intake Heater Relay Compatible with Select Dodge Models

The Dorman 904-356 Intake Heater Relay is a direct replacement for the original engine air intake heater relay on select Dodge models. This relay is an ideal solution for a damaged or failed original part and is made from quality components for reliable performance and a long service life. To ensure proper fit, input your vehicle's make, model, and trim level into the garage tool. Backed by a team of product experts with over 100 years of automotive experience, you can trust the quality of this durable construction relay.

9.5
FTB Score

What We Like

  • Direct replacement for original relay
  • Durable construction for reliable performance and long service life
  • Backed by team of product experts with over a century of automotive experience
#TOP 5

Dorman 904-308 Intake Heater Relay

Dorman 904-308 Intake Heater Relay Cover

Dorman 904-308 Intake Heater Relay Compatible with Select Dodge Models

The Dorman 904-308 Intake Heater Relay is a direct replacement for the original part on specified Dodge models. The relay is made from quality components to ensure reliable performance and long service life. It is the ideal solution for a damaged or failed original part. To ensure fit, users can input their make, model, and trim level into the garage tool. Backed by a team of product experts in the United States and over a century of automotive experience, this relay is trustworthy and reliable.

9.5
FTB Score

What We Like

  • Direct replacement for original part
  • Made from quality components for reliable performance and long service life
  • Backed by a team of product experts and over a century of automotive experience
#TOP 6

EATAKWARD Intake Manifold Heater Relay

EATAKWARD Intake Manifold Heater Relay Cover

EATAKWARD 68188401AA Intake Manifold Heater Relay, Air Intake Relay, Replacement for Dodge for Ram 2500 3500 Pickup 1994-2002 5.9L Diesel Grid Sturdy Wear-Resistance 56026842 904-308

EATAKWARD Relay is a top-quality replacement part for Dodge RAM 2500 and 3500 models from 1994 to 2002. It offers OE quality components, ensuring long-lasting performance in extreme conditions. The perfect fit and function save you time during installation. Say goodbye to cold start problems with this relay, preventing issues like unable cycle off or inlet heater errors. Its wide compatibility makes it a reliable choice for your vehicle.

9.4
FTB Score

What We Like

  • OE quality components
  • Perfect fit
  • Solves cold start problems
#TOP 7

Xspeedonline Relay Solenoid Heater for Dodge RAM 2500/3500 Diesel

Xspeedonline Relay Solenoid Heater for Dodge RAM 2500/3500 Diesel Cover

Premium Relay Solenoid AIR Intake Heater Grid for Dodge RAM 2500 3500 Cummins Diesel 5.9

The Xspeedonline Dodge RAM Heater Relay is designed to meet or exceed original equipment standards, ensuring reliable performance you can trust. This relay is thoroughly tested during manufacturing, so you won’t have to worry about faulty parts. It directly replaces several part numbers, making it easy to find the right fit for your vehicle. Perfect for 1994-2002 Dodge Ram 2500 and 3500 diesel models, this relay supports your engine’s air intake heater system, helping your diesel engine start smoothly in cold conditions. If you’re unsure about compatibility, the detailed photos and part numbers help you confirm the right product for your needs.

9.4
FTB Score

What We Like

  • OEM quality standards
  • Fully tested reliability
  • Multiple part replacements
  • Fits 1994-2002 Dodge RAM
#TOP 8

Casalytics Atwood 93849 Water Heater Relay

Casalytics Atwood 93849 Water Heater Relay Cover

Power Relay for Atwood 93849 Water Heater Relay (Pack of 2) – 12VDC 30A SPST-NO for Dsi Water Heaters - Replaces AZ2280-1A-12D, AZ22801A12D

The Casalytics Atwood Relay is designed as a direct replacement for specific Atwood water heater parts, ensuring it fits your system perfectly without hassle. It supports a high electrical load of 30 amps, which means it can handle the power needed to reliably ignite and operate your RV’s water heater, helping you avoid unexpected failures. Its Single Pole Single Throw (Normally Open) design provides steady and safe power flow, making sure your water heater starts quickly and efficiently. Built tough with silver-alloy contacts and a heat-resistant case, this relay can endure extreme temperatures and vibrations, giving you dependable performance in your RV environment.

9.2
FTB Score

What We Like

  • OEM direct replacement
  • High 30A current capacity
  • Stable SPST-NO design
  • Durable construction
#TOP 9

Packard Therm-O-Disc Heat Relay

Packard Therm-O-Disc Heat Relay Cover

Replacement for Therm-O-Disc 12S20-5 KW Heat Sequencer Relay

The Packard Heat Sequencer Relay is designed to handle up to 25 Amps at both 120 and 240 Volts, ensuring reliable performance in your heating and cooling systems. Its full-load rated auxiliary contacts enhance the relay's functionality, allowing you to control additional components efficiently. Built to resist shock and vibration, this solid-state device ensures durability and longevity, making it a smart investment for your HVAC needs. The quick-connect terminals simplify installation, saving you time and effort while ensuring a secure connection.

9.1
FTB Score

What We Like

  • High current capacity
  • Durable construction
  • Easy installation
  • Reliable performance
#TOP 10

X AUTOHAUX Intake Manifold Heater Relay

X AUTOHAUX Intake Manifold Heater Relay Cover

X AUTOHAUX Intake Manifold Heater Relay for Dodge Ram 2500 3500 Pickup 1994-2002 5.9L Diesel Grid Heater Sturdy Wear-Resistance 56026842 904-308

The X AUTOHAUX Intake Manifold Heater Relay is a reliable and sturdy accessory designed for Dodge RAM 2500 and 3500 with 5.9L L6 Diesel engines from 1994 to 2002. This intake heater relay is built with high-quality components to ensure a prolonged service life and excellent performance even in extreme conditions. By replacing your old or damaged relay with this one, you can avoid cold start problems, cycle off issues, and inlet heater errors. The direct bolt-on installation makes it easy to replace, providing you with the convenience of a quick and hassle-free upgrade. With the X AUTOHAUX Intake Manifold Heater Relay, you can ensure a smooth and reliable start for your vehicle.

9.1
FTB Score

What We Like

  • Reliable
  • Sturdy
  • Prolonged service life

Frequently Asked Questions (FAQs)

1. What is the function of the heater relay?

The heater relay in a furnace is responsible for transmitting electrical power to the heating elements and blower motor inside the furnace cabinet. It allows the heating elements to generate heat and the blower motor to distribute the warmed air through the ductwork, ensuring efficient heating in the system.

2. How do I know if my furnace relay is bad?

To determine if a furnace relay is faulty, you can check if the LED lights on modern relays are active. If the LED light is not functioning despite having control voltage to the coil terminals or the relay, it is likely that the relay is defective and needs to be replaced.

3. What is the difference between a thermostat and a relay?

A thermostat and a relay serve different functions in an electrical circuit. A thermostat is typically a low voltage device, usually operating at 24V, while the HVAC equipment it controls operates at line voltage. The relay acts as an intermediary, allowing the thermostat to control the equipment by bridging the voltage difference between the two. This ensures that the thermostat and the equipment can be in separate circuits and still work together effectively.

Editor's Notes

During our auxiliary heater & ac control relay research, we found 24 auxiliary heater & ac control relay products and shortlisted 10 quality products. We collected and analyzed 6,290 customer reviews through our big data system to write the auxiliary heater & ac control relays list. We found that most customers choose auxiliary heater & ac control relays with an average price of $18.70.

The auxiliary heater & ac control relays are available for purchase. We have researched hundreds of brands and picked the top brands of auxiliary heater & ac control relays, including Dorman, X AUTOHAUX, Xximuim, EATAKWARD, Xspeedonline. The seller of top 1 product has received honest feedback from 384 consumers with an average rating of 4.7.

Written by

Robert Reyes Avatar

Robert Reyes

Robert Reyes is a dedicated writer from San Francisco with a bachelor of degree in mechanics and a bachelor of degree in marketing. He focuses on making some complicated topics simple and enjoys explaining complex and technical things in an easy-to-understand way.