1

Check that the HVAC unit is plugged into it's power source and if applicable that the external power switch for the HVAC unit is turned on

Some HVAC units may have an external power switch that is on the unit or somewhere within the room

2

Check that the HVAC unit is receiving power from it's power source

Even though the unit is connected to it's power source it may not actually be receiving power from that source

3

Check that the HVAC Controller is plugged/screwed into the HVAC unit appropriately

Some HVAC units require that the HVAC Controller be plugged in and some require them to it be screwed in. Use the below link find the appropriate PTAC or VTAC Configuration Guide for the make and model of HVAC unit that you are working on and confirm that the unit is plugged or screwed in appropriately

PTAC & VTAC Configuration Guides

4

Check that the HVAC Controller is receiving power from the HVAC Unit

This can be checked by looking at the green LED at the bottom of the HVAC Controller. This is located inside the small hole next to the pin header connections. Below are the possibilities of how the light could appear

• No light present - Confirm that steps 1 through 3 of this guide have been completed. If each step is verified then it is possible that the HVAC Controller is damaged and needs replaced. This can be tested by hooking up a new HVAC Controller to the HVAC unit. If the new HVAC Controller powers up then the old one is bad, and if it doesn't power up then the issue lies somewhere between steps 1 and 3

• Light on and flashing at the same rapid interval - This happens after 15-20 seconds after the HVAC Controller powers up. This means that the HVAC Controller is not receiving appropriate power from the HVAC unit's 24V interface. This is an HVAC unit issue that will require the HVAC unit's 24V interface be repaired

• Light on and staying solid - Good working condition

• Light on and flashing at random intervals - Good working condition