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

Vacuum switch C sends signals to the control unit when the vacuum falls below 60 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 2 (Yellow/Red (+)) and 32 (Black (-)).

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

A) Create a vacuum greater than 60 mm Hg.

Measure the voltage between pins 2 (Yellow/Red (+)) and 32 (Black (-)).

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

If there is no voltage, then vacuum switch C 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/Red (-) terminals on the main wiring harness.

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

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

If there is battery voltage, then you should repair the break in the Yellow/Blue wire between the control box and terminal 8 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.

[The text was taken from the website: HONDABOOK.ru]