a) Connect the negative probe of the ohmmeter to the positive terminal of the rectifier block, and connect the positive probe in series to each of the other three terminals.
Make sure there is conductivity (closed circuit) in all three dimensions.
b) Reverse the polarity of the tester probes and repeat the procedure in point c). Make sure that the circuit is open in all three dimensions (resistance tends to infinity).
If the conditions are not met, replace the rectifier unit.
2. Checking the negative valve.
a) Connect the positive probe of the ohmmeter to the negative terminal of the rectifier unit, and connect the negative probe in series to each of the other three terminals. Check for conductivity (closed circuit) in all three dimensions.
b) Reverse the polarity of the tester probes and repeat the procedure in point "a". Make sure that the circuit is open in all three dimensions (resistance tends to infinity).
If the conditions are not met, replace the rectifier unit.