Four Seasons 91591 HVAC Heater Core

Four Seasons 91591 Heater Core Overview

The Four Seasons 91591 heater core is a copper/brass HVAC heater core built for direct replacement service in heating and defrost systems. With a 6 in. core height, 9-3/4 in. core width, and 2 in. core depth, it is sized for applications that require a compact, OE-style heater core assembly.

Compatible With select Ford truck and SUV heater core applications, this Four Seasons heater core is a practical replacement for restoring cabin heat and windshield defrost performance. The Four Seasons Heater Core line focuses on replacement parts that meet or exceed OEM requirements, and part number 91591 is built to match the original-style copper/brass construction used in many older HVAC systems.

Key Features

• Part number 91591 heater core from Four Seasons
• Copper core material with copper/brass heater core style
• Core dimensions: 6 in. height, 9-3/4 in. width, 2 in. depth
• Tube sizes: 0.625 in. and 0.750 in.
• Meets or exceeds OEM requirements
• Direct-fit HVAC heater core replacement for select Ford applications

Detailed Product Description

The Four Seasons 91591 is a heater core / copper brass unit designed for vehicles that use a traditional copper/brass HVAC core. Its dimensions and tube sizing make it a strong match for restoration and maintenance work where the original heater core has leaked, restricted flow, or lost heat transfer efficiency. If you are searching for a Ford heater core replacement, a truck heater core, or an HVAC heater core for classic Ford applications, part number 91591 is a relevant OE-style option.

This part cross-references Gates 6830 for the same application. It also cross-references Nissens 94591 for the same application.

What This Heater Core Helps Solve

• Weak or inconsistent cabin heat
• Coolant seepage from a corroded heater core
• Fogged windshield caused by poor defrost output
• Restricted coolant flow through the HVAC heater circuit
• Replacement needs after heater core failure in Ford truck and SUV systems

Installation Notes and Tips

Verify core height, width, depth, and tube diameters against the original unit before installation. Confirm hose routing and pipe orientation on the vehicle, since adjustable pipe positioning is not included on this part. For best results, inspect the cooling system for contamination or debris before installing the new heater core, and flush the system if the old core failed from corrosion or blockage.

Fits select Ford truck and SUV heater core applications; confirm the original part dimensions and tube sizes match Four Seasons 91591 before ordering. For Ford heater core replacement work, use the vehicle’s HVAC layout and hose connections as the final fitment check.

Quality Assurance

Four Seasons lists this heater core as meeting or exceeding OEM requirements. The copper/brass construction supports OE-style service replacement in applications that originally used this material specification.