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Four Seasons 74804 HVAC Heater Control Valve
| Brand | Four Seasons 74804 |
|---|---|
| Description | Vacuum Closes Non-Bypass Heater Valve |
| Hose Connector Quantity | 3 Connectors |
| Material | Plastic |
| O.E. Replacement? | Yes |
| Opening B IN | 0.750 |
| Opening B MM | 19.050 |
| Opening C IN | 0.750 |
| Opening C MM | 19.050 |
| Opening D IN | 0.625 |
| Opening D MM | 15.875 |
| Opening IN | 0.750 |
| Opening MM | 19.050 |
| Operation Type | Vacuum |
| Style | Non-Bypass |
| Type | Heater Valves |
| Product line | Heater Valve |
| Fits | Cadillac · 4 vehicles |
OE replacement. Direct-fit heater valve for straightforward service.
Vacuum-operated. Responds to vacuum control for reliable heater flow.
Non-bypass design. Helps route coolant through the heater circuit efficiently.
Cross-references Eastern Catalytic 30318, Four Seasons 74804 and Monroe Shocks & Struts 5928 for the same application. See all 15.
Four Seasons 74804 Heater Valve Overview
The Four Seasons 74804 heater valve is an OE replacement HVAC heater control valve for vacuum-operated heating systems. It uses a non-bypass design with three hose connectors and plastic construction to regulate coolant flow through the heater circuit on select Cadillac applications.
Compatible with 1986-1987 Cadillac Eldorado and 1986-1987 Cadillac Seville, this heater valve is built for direct replacement service in vacuum-controlled temperature systems. Four Seasons Heater Valve 74804 is a practical choice when the original valve no longer opens and closes correctly.
Key Features
- Vacuum-operated HVAC heater control valve
- Non-bypass style for direct heater circuit flow control
- OE replacement design for factory-style fitment
- Three hose connectors for the specified coolant routing
- Plastic body construction
- Opening sizes: 0.750 in. (19.050 mm) and 0.625 in. (15.875 mm)
Product Details
Four Seasons 74804 is part of the Heater Valve product line and is engineered as an OE replacement HVAC heater control valve. The vacuum-close, non-bypass configuration is used to control coolant flow to the heater core based on HVAC demand, helping maintain proper cabin temperature control in supported Cadillac Eldorado and Cadillac Seville models. This part cross-references Monroe Shocks & Struts 5928 for the same application.
Common Issues This Part Can Address
- Heater output stuck on or stuck off
- Loss of cabin heat control from a failed vacuum valve
- Coolant flow not shutting off through the heater circuit
- Temperature control inconsistency in the HVAC system
- Vacuum-actuated heater valve leakage or malfunction
Installation Notes and Tips
Verify hose diameter and connector layout before installation, especially the 0.750 in. and 0.625 in. openings. Confirm the vacuum line routing matches the vehicle’s HVAC control strategy, and inspect adjacent coolant hoses for wear, swelling, or cracking before reassembly. Proper coolant refill and system bleeding are recommended after replacement.
Quality Assurance
Four Seasons 74804 is an OE replacement heater valve built to match the original application requirements for vacuum-operated HVAC systems. It is listed for 1986-1987 Cadillac Eldorado and 1986-1987 Cadillac Seville.
| Year | Make | Model | Position | Notes |
|---|---|---|---|---|
| 1987 | Cadillac | Eldorado | N/A | Heater Valve |
| 1987 | Cadillac | Seville | N/A | Heater Valve |
| 1986 | Cadillac | Eldorado | N/A | Heater Valve |
| 1986 | Cadillac | Seville | N/A | Heater Valve |
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