Hi!
I have two dual-packs on my roof, with identical thermostats. I like to run them in the "fan" mode early in the morning with the windows open to get some cool air throughout the house.

This morning the blower fan for thermostat "A" would not run in the "cool" mode, nor the "off" mode. For thermostat "B", the fan will run in "off" or "cool".

I can hear the "click" come from the "A" thermostat as I cycle the fan switch on/off. In the "cool" mode I lowered the temp setpoint down to turn on the A/C. The compressor came on, however the blower never came on. I verified 240VAC on the roof at the unit and 120 VAC at the circuit board. The red indicator light on the circuit board was illuminated. When the fan switch was cycled at the thermostat, one (or both) relays on the board appeared to "click".

The blower motor has 5 wires coming out of it. The five connection points are labeled: "1", "2", "H", "M", "L" The motor is labeled "1 phase".

At which two points would I apply 120 VAC to see if the motor will turn?

The system worked fine yesterday. Where should I start? What else can I check on the circuit board or at the motor?

Thanks!
Derek

Check fuses and circuit breakers first

Hi!
I have two dual-packs on my roof, with identical thermostats. I like to run them in the "fan" mode early in the morning with the windows open to get some cool air throughout the house.

This morning the blower fan for thermostat "A" would not run in the "cool" mode, nor the "off" mode. For thermostat "B", the fan will run in "off" or "cool".

I can hear the "click" come from the "A" thermostat as I cycle the fan switch on/off. In the "cool" mode I lowered the temp setpoint down to turn on the A/C. The compressor came on, however the blower never came on. I verified 240VAC on the roof at the unit and 120 VAC at the circuit board. The red indicator light on the circuit board was illuminated. When the fan switch was cycled at the thermostat, one (or both) relays on the board appeared to "click".

The blower motor has 5 wires coming out of it. The five connection points are labeled: "1", "2", "H", "M", "L" The motor is labeled "1 phase".

At which two points would I apply 120 VAC to see if the motor will turn?

The system worked fine yesterday. Where should I start? What else can I check on the circuit board or at the motor?

Thanks!
Derek
I have power up to the unit. Circuit board light (red) is on. Relay(s) on the board click when the thermostat button for "fan" is selected. Which of the 5 wires into the motor would the correct ones to test with 115 VAC?

Check your wiring diagram on the access door or blower door.

Wire color probably white and black. White common/neutral and black is the hot leg.

If this is on a roof top please make sure the unit is electrically grounded for your safety while testing live voltage. Usually this is done with a green or bare copper wire. This wire is usually pulled along with the neutral and black wires that are used to power up the unit and the ground should already be on the unit. It is just good to check before doing electrical testing especially when testing motors.

Hi!
I have two dual-packs on my roof, with identical thermostats. I like to run them in the "fan" mode early in the morning with the windows open to get some cool air throughout the house.

This morning the blower fan for thermostat "A" would not run in the "cool" mode, nor the "off" mode. For thermostat "B", the fan will run in "off" or "cool".

I can hear the "click" come from the "A" thermostat as I cycle the fan switch on/off. In the "cool" mode I lowered the temp setpoint down to turn on the A/C. The compressor came on, however the blower never came on. I verified 240VAC on the roof at the unit and 120 VAC at the circuit board. The red indicator light on the circuit board was illuminated. When the fan switch was cycled at the thermostat, one (or both) relays on the board appeared to "click".

The blower motor has 5 wires coming out of it. The five connection points are labeled: "1", "2", "H", "M", "L" The motor is labeled "1 phase".

At which two points would I apply 120 VAC to see if the motor will turn?

The system worked fine yesterday. Where should I start? What else can I check on the circuit board or at the motor?

Thanks!
Derek
End of story: Run capacitor was bad. Replaced for about $10.

Thanks for the help!

Derek

Good deal.