Checking the functionality of the vacuum switch B (Honda Accord 3)

Vacuum switch B sends signals to the control unit when the vacuum falls below 30 mmHg.

Disconnect vacuum hose #7 from the vacuum manifold and connect a vacuum pump to the hose.

Turn on the ignition.

Measure the voltage between pins 8 (Yellow/Blue (+)) and 32 (Black (-)).

If there is battery voltage, then see point A), if not, then point B).

A) Create a vacuum greater than 30 mm Hg.

Measure the voltage between pins 8 (Yellow/Blue (+)) and 32 (Black (-)).

If there is voltage, then vacuum switch B should be replaced.

If there is no voltage, then vacuum switch B is normal.

B) Turn off the ignition.

Disconnect the 4-pin connector on the control box.

Turn on the ignition.

Measure the voltage between the Black/Yellow (+) and Yellow/Blue (-) terminals on the main wiring harness.

If there is voltage, then vacuum switch B should be replaced.

If there is no voltage, then measure the voltage between Black/Yellow (+) and ground.

If there is battery voltage, then you should repair the break in the Yellow/Red wire between the control box and terminal 2 of the control unit.

If there is no voltage, then you should repair the break in the Black/Yellow wire between fuse #1 and the control box.