Four Seasons 74855 HVAC Heater Control Valve - Rear

Four Seasons 74855 Heater Valve Overview

The Four Seasons 74855 is an OE replacement HVAC heater control valve built for vacuum-operated bypass systems. It uses a plastic body with two 5/8 in. hose connectors and is designed for rear heater control on select Chevrolet Astro and GMC Safari applications.

Four Seasons Heater Valve line parts are built for direct-fit temperature control service, making this valve a practical choice when restoring coolant flow control in the heater circuit. This part number, 74855, is listed for rear-position applications and matches the original-style vacuum open bypass design used on the covered vehicles.

Key Features

• Vacuum open bypass heater valve for HVAC temperature control
• OE replacement design for direct-fit service
• Plastic construction
• Two hose connectors
• 5/8 in. openings: 0.625 in. / 15.875 mm
• Rear-position application coverage
• Four Seasons 74855 heater valve

Detailed Product Description

This HVAC heater control valve regulates coolant flow through the heater circuit using vacuum operation and a bypass-style layout. It is specified as a vacuum open bypass heater valve, which means it follows the original control strategy used in the listed applications. The 74855 part number is an OE replacement for service on 1996-2005 Chevrolet Astro and GMC Safari rear heater systems, including 2001-2005 Chevrolet Astro, rear, w/o Recreation Upfitter Package; 2001-2005 GMC Safari, rear, w/o Recreation Upfitter Package; 1996-2000 Chevrolet Astro, rear, valve, w/o bracket; and 1996-2000 GMC Safari, rear, valve, w/o bracket.

This part cross-references Monroe Shocks & Struts 801803 for the same application. Four Seasons 74855 is also referenced under NGK 5958 in interchange data.

What This Heater Valve Helps Address

• Rear heater output stuck on or stuck off
• Improper coolant routing through the heater circuit
• Loss of vacuum-controlled heater valve operation
• Temperature control issues in the rear HVAC system
• Replacement of a worn or leaking OE-style heater valve

Installation Notes and Fitment

Compatible with 1996-2005 Chevrolet Astro, rear, and 1996-2005 GMC Safari, rear, with the exact notes listed above. Fits 2001-2005 Chevrolet Astro, rear; fits 2001-2005 GMC Safari, rear; fits 1996-2000 Chevrolet Astro, rear; and fits 1996-2000 GMC Safari, rear. Verify hose size, vacuum routing, and the original valve style before installation to confirm the 5/8 in. connector openings and bypass configuration match the vehicle’s HVAC plumbing.

Quality Assurance

Four Seasons 74855 is an OE replacement heater valve from the Four Seasons Heater Valve product line, built to match the original vacuum-operated bypass design used in the listed Chevrolet Astro and GMC Safari applications.