NXH542GKA100 The air handler is not working

green goes to g on air-handler,white goes to w on air-handler yellow goes to outside condensor, red from air-handler goes to rh-rc on thermostat, whire off c on air-handler goes to outside condensor.

What's wrong with your current AHU? Any Ruud dealer can assist you. Most 4 ton units work with r-22 or 410a. As a side note, most parts in an air handler can be replaced unless the case is rusted thru.

You have a bad sequencer on the air handler.

Generally, you would go from the thermostat to the air handler, and then, from the air handler to the outdoor unit. I don't know if you have a heat pump or not, so I will give you a simple diagram and you can contact me if you need more.

Thermostat : Y G R W and sometimes C
Air handler: Y G R W and C
Outdoor unit: two wires connecting to the contactor ( not heat pump)

Thermostat; Y--------------Y(air handler cooling)------------------one side of contactor, outdoor unit
G-------------G (air handler, fan)
R--------------R (air handler ,hot)
W-------------W (air handler, heat)
C--------------C (air handler, common)------------other side of contactor, outdoor unit

This is a typical wiring diagram. Just contact me if you have something different. Hope this helps. Stay cool. mark

Hello, you need the wires connected at Y and C for the contactor to energize the condenser.

any 4 tonnes air handler will fit if you respect de gas for the unit if r22 than than r 22 air handler if r410 than r410 air handler you can put r410 air handler if r 22 not avalable but be sure that expension valve is compatible.

I could not find a "fault code" list for the LA125HV but for thier Multi Split Units LG lists code CH7 (C7) as "Indoor Unit is Set in Different Cool/Heat Operation Mode." So maybe your air-handler tihinks it's in Heat mode will the compressor is in Cool mode, or vice-versa....

Have you hard wired your fan motor to verify that the motor and or the capacitor are good? If you do a continuity test of the motor leads(with electricity off of course) you can see if the motor has open or grounded windings.

We tried to bypass at the Tstat. Thanks for your time and interest.

yes and that's dangerous as fumes and exhaust may enter the house