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Honeywell M9185D 1004 Modutrol

icesailoricesailor Member Posts: 7,265
Can anyone tell me how to troubleshoot a Honeywell M9185D Modutrol with a T991A Potentiometer controller?

It runs a Honeywell modulating water valve for a heat recovery unit in a nursing home. The valve stopped modulating. I can open it by jumping the 24 volt Red to Blue, it will open the valve. I got the manual off the Internet but it doesn't tell me how to troubleshoot/test it electrically. I understand how it works, just not how to test it.


  • RJRJ Member Posts: 459

    This is a series 90 actuator (135 ohm )   testing should be done with actuator disconnected from valve linkage.  r-b opens valve like you did,  jumpering r-w should close valve (rotate the opposite way)   or  install potentiometer per instructions rotating dial on t991a will add or take away resistance to motor circut,  If motor does'nt move and there is no voltage drop to your 24 volt supply I would recheck all connections, If this does'nt work I would replace it, not alot to troubleshoot on inner motor workings,  make sure your valve is not bound up which is the biggest cause of actuator failure   You might consider replacing the valve,actuator and linkage        contact    for additional info
  • RJRJ Member Posts: 459

    forgot to say that when testing actuator external wires on r.w.b  terminals should be  removed , only 24v wiring hooked up.  also t991a is a modulating temp. control.  i recommend that you install a manual potentiometer to test motor,  honeywell makes one, not sure of part no.
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