No Heat / Intermittent Heat - Heater Control Valve VSV Replacement

Electricalbeginner✓ OP Confirmed

Problem

The heater water valve's electric VSV (Vacuum Switching Valve) fails, preventing vacuum from reaching the water valve actuator. This keeps the valve closed so hot coolant cannot flow through the heater core, resulting in no cabin heat.

No heat from heaterIntermittent heat (sometimes works, sometimes not)VSV solenoid reads open (failed windings)No vacuum reaching heater water valve actuator

Root Cause

The electric VSV (vacuum switching valve, OEM part 88690-14820) solenoid windings fail open over time. This VSV controls vacuum to the heater water valve actuator — when it fails, vacuum cannot reach the actuator to pull open the water valve, so coolant flow to the heater core is blocked and the cabin gets no heat.

Confidence

High confidence — Original poster confirmed this resolved the issue

View Original Thread →Posted December 2023 on SupraForums.com