Vacuum switch C sends signals to the control unit when the vacuum falls below 60 mm. rt. Art.
Disconnect the #7 vacuum hose from the vacuum manifold and connect a vacuum pump to the hose.
Turn on the ignition.
Measure voltage between 2 (Yellow/Red (+)) and 32 (black (-)) contacts.
If there is battery voltage, then see paragraph A), if not - item B).
A) Create a vacuum over 60 mm. rt. Art.
Measure voltage between 2 (Yellow/ Red (+)) and 32 (black (-)) contacts.
If voltage is present, replace vacuum switch C.
If there is no voltage, then vacuum switch C is OK.
B) Switch off the ignition.
Disconnect the 4-pin connector on the control box.
Turn on the ignition.
Measure the voltage between Black/Yellow (+) and Yellow/Red (-) contacts on the main wiring harness.
If voltage is present, replace vacuum switch C.
If there is no voltage, then measure the voltage between Black/Yellow (+) contact and weight.
If there is battery voltage, repair the open in the Yellow/Blue wire between the control box and terminal 8 of the control unit.
If there is no voltage, then repair the break in the Black/Yellow wire between the #1 fuse and the control box.