I have a conventional heating and cooling unit for my condo. This is not a heat pump. The outside unit is a Rheem. The problem I am having is that when I turn on my heat, the settings are set to fan-auto, system-heat, I have no heat coming out of the vents just plain air. Now if I set the fan to the on mode, the heater works perfect. This problem just started happening as before I was able to set the fan to auto in the heat mode and everything worked just fine. Could someone please give me some insight on this so I can fix this problem. Thank you.

Gas unit? Likely a faulty combination fan/limit control. Electric? Likely the fan switch on the sequencer. Interim continuous fan won't hurt anything. Post brand and model # of indoor unit.

I believe the brand is Goodman, and the model number is AW30-08C, or 0BC, I could not determine if the 8 was a b or not. This is an electric unit.

If memory serves me, this unit uses a time-delay blower relay that is similar to a sequencer and prone to failure. I have replaced many of these with a conventional fan relay for improved reliability.

If possible do you think you could tell me where I might find the relay at, I have taken the cover off and I can see the blower. Is this something that I can replace myself or do I need to have a technician do this? Thanks so much for your help.

This will depend upon your ability to follow directions. The most common relay used for this purpose is a Honeywell R8222D1014. You will have to locate the fan control - do you know how to read a wiring diagram?

Yes I do.

Look at the component legend for a description of a fan control device and locate it on the diagram. Identifying the wire colors and destinations will help you identify the actual part we are seeking in the unit. P.S. turn off power supply...

Could there be another name other than a fan control device, Im not seeing anything listed like that in the legend.

Yes, look for something similar. Or, if you follow the wires from the blower motor, at least one will take you to it.

I believe I might of found it, but I'm not certain.

Identify the component on the diagram and post the description from the legend. Or, if you can post the component list from the legend, I can identify it by description.

Circuit breaker, evaporator motor, blower time delay relay, relay, run capacitor, thermal limit, transformer, heat element. This is what is showing on the legend.

Blower time-delay relay... just as I suspected... how many wires connected to it, and how many terminals used?

7 wires connected to it, all terminals being used.

This is where things get a little sticky as I am not there to see the wiring. Some of these wires are "just passing through" and not controlled by the relay. Follow along with me: the 2 opposing wires on the bottom of the relay stack are low-voltage. Following one will end up at the "G" input; the other will end up at the low voltage common circuit - perhaps not directly, but eventually if "hopscotched" with other low voltage components. This is a test: identify and understand these two circuits. I need to know that this is understandable to you before I can recommend you attempt this yourself. If you are uncomfortable with this, I would recommend hiring a pro.

That is a little confusing to me, however the blower time delay relay is all on piece, would I fix the issue by replacing that relay?

If you replace it with an identical part, everything should match up as you see it now but it will fail again someday. Installing a conventional relay is a little more involved but more reliable.

Well thank you very much for your help. Happy holidays to you.

Likewise and good luck.