GLC & 626 Models

From a cold engine, disconnect vacuum amplifier-to-thermo valve vacuum tube. Disconnect No. 1 purge control valve-to-thermo valve vacuum tube from thermo valve (under intake manifold).
Start engine and run at 2000 RPM (1500 RPM for GLC Wagon and 626 models). No vacuum should be felt at either port. See Fig 1.

Fig 1: Water Thermo Valve Test Connections (GLC & 626 Models)
Courtesy of MAZDA MOTORS CORP.

Connections are reversed on 626 models.
Warm engine until coolant temperature is 131°F (55°C) on GLC models, 138°F (59°C) on GLC Wagon models or 114-129°F (46-54°C) on 626 models.
With engine at proper temperature, vacuum should be felt. If valve does not respond as outlined, replace water thermo valve.
NOTE: Testing of Mazda 626 thermo switch is explained in "MAZDA PISTON ENGINE AIR INJECTION" article in this section.