York YSTMQMQK1 Steam driven

[chillerguru]

I have a question regarding the expansion module I/O board that sends the vacuum pump #2 a run signal to a 110 volt contactor. the I/O board has a dc relay that energizes the 110 volt contact to pump contactor. the relay is good and has been swapped, the 5 amp fuse is also good and has been swapped, the pump contactor coil is also good. the problem I'm having is the 110 volt coming out of terminal is intermittent and causes pump contactor to chatter , all wiring has been check for continuity and breaker overload contact. I'm at the point to condemn the I/O expansion module. The vacuum pump make up water strainer is clean, the solenoid is good and the flow switch is also working. I'm sure this expansion I/O board is commonly used even on non steam chillers. Any ideas will be helpful.

[HYP1278]

Suppressor. Overload. Loose connection in plug 38

[chillerguru]

the 120 volt coming out of the I/O board is intermittent. the overload contact is good, and no loose connections on splicing terminal board or plug type cable connector. the coil on the contactor has no suppressor, should one be installed.

[HYP1278]

Looking at wiring diagram not much between i/o and m6. Triac could be faulty or plug.