Four Seasons 91777 HVAC Heater Core

Four Seasons 91777 Heater Core Overview

The Four Seasons 91777 heater core is a copper/brass HVAC replacement built for vehicles that need dependable cabin heat and OE-style fitment. With a copper core material and dimensions of 7-5/8 in. long, 6 in. wide, and 1-7/8 in. thick, it is made to match the original heater core layout in supported Ford, Mazda, and Mercury applications.

This Four Seasons heater core 91777 meets or exceeds OEM requirements and uses a copper/brass heater core style for direct replacement service. It is a practical choice for 2001-2007 Ford Escape, 2005-2007 Mercury Mariner, 2001-2006 Mazda Tribute, 1993-1997 Ford Probe, 1993-1997 Mazda 626, and 1993-1997 Mazda MX-6 heating system repairs.

Key Features

• Part number: 91777
• Four Seasons Heater Core line
• Copper core material with copper/brass construction
• Core dimensions: 7-5/8 in. height, 6 in. width, 1-7/8 in. depth
• Tube size: 0.625 in. / 15.875 mm on both connections
• Meets or exceeds OEM specifications
• Fixed pipe positioning
• Direct-fit HVAC heater core replacement

Detailed Description

The Four Seasons 91777 heater core is engineered for HVAC systems that use a copper/brass design and standard dual 0.625 in. tube connections. Its compact core size and OE-style layout support proper routing inside the heater case, helping restore heat transfer performance in the cabin. This part cross-references APDI 9010250 and Hayden 2673 for the same application.

Compatible With 2001-2007 Ford Escape, N/A; 2005-2007 Mercury Mariner, N/A; 2001-2006 Mazda Tribute, N/A; 1993-1997 Ford Probe, N/A; 1993-1997 Mazda 626, N/A; and 1993-1997 Mazda MX-6, N/A. The Four Seasons 91777 is also a relevant search match for drivers looking for a Ford Escape heater core, Mazda Tribute heater core, or Mercury Mariner heater core replacement.

Common Problems This Part Can Address

• Weak or uneven cabin heat
• Coolant seepage inside the HVAC case
• Fogging or sweet odor from a leaking heater core
• Restricted coolant flow through the heater circuit
• Heat loss caused by a damaged or corroded core

Installation Notes and Tips

Verify the core dimensions, tube diameter, and fixed pipe position against the original unit before installation. Because heater core replacement often requires access through the HVAC case, inspect related hoses, clamps, and coolant condition during service. Confirm fitment by vehicle year, make, and model before ordering the Four Seasons 91777 heater core.

Quality Assurance

This heater core is listed as meeting or exceeding OEM requirements and is built in the Four Seasons Heater Core product line for replacement use in supported Ford, Mazda, and Mercury vehicles.