My heat pump unit outside unit works.The attic furnace and air duct fans just stopped working.I'm not getiing manual fans either

With a non heat pump it is a simple 24 volt AC control circuit. In the attic there is a relay that is actuated via the fan control wire directly from the thermostat. On the thermostat there is an auto/man switch that controls the fan. Manual the fan runs all the time. Auto fan turns on and off with the outside compressor.

If the system is not calling for cool and the fan continues to run the fan relay is sticking. common problem. Sometimes after running for several days the relay will stop sticking if not, replace relay.

If the system is calling for cool and the compressor stops I would still expect the fan to run until thermostat tells the A/C to off. Some compressor units include a safety switch or high-pressure cut-out switch A blocked internal valve bad control board or external fan in outside unit defective no air flow in outside unit.
High pressure cut out not good,

Suggest turning temp max cool and observe. If acceptable cool and the compressor runs without interruption all is good, except for the blower in the attic. Safely check relay in attic blower circuit.

Hope this helps.

Your dehumidifier is likely working correctly. When operating and removing moisture, a dehumidifier will supply warm/hot air to your house. Your dehumidifier moves less air than your A/C, so your supply ductwork in your house is oversized for the dehumidifier. This will lead to uneven feeding of your supply duct branches with just the dehumidifier operating.

Since your dehumidifier is installed in the attic, make sure that the ducting connected to it is well insulated. Also make sure that your dehumidifier cabinet is insulated. These actions will help prevent heat gain from the hot air in your attic.

Is your dehumidifier bringing in fresh air from outside? If the outside air is hot and humid, the dehumidifier will supply warmer air to your home.

Some people run their A/C fans continuously to help with the air distribution, but this is a bad idea since it increases energy usage considerably.

DryDog

Just guessing, but I'll bet your 2nd floor duct work is in the attic, and uninsulated, wrapping all attic mounted duct work with R-13 insulation and sealing it with tape will help but there is still going to be a slug of cold air pumped into the upstairs rooms each time the furnace cycles.

Please provide more info. When it goes off does it come back on by itself or do you have to flip a breaker? Is the furnace gas or electric? If it is not moving enough air across your heat exchanger in a gas furnace or across electric heating elements this will trip a safety switch that will stop heating but not fan. Low air speed is most likely from inexperienced or improper duct design/ installation. Duct sizing is very important to move enough air. Don't believe me try breathing thru a straw. If your unit is a gas furnace it has a flashing code that will tell you what is wrong codes listed inside unit door. Could be lots of things. Reply with more info.

The attic fan is not a part of your a/c system, and you should not run it while you are running the a/c. If you are currently using the attic fan, it is possible that someone wired it so that the a/c won't turn on while the attic fan is on. Otherwise if the thermostat is set below room temp, and says it is calling for cool, then the problem is most likely coming from an issue at the outside unit itself. Make sure to check your fuses, at the fuse panel and outside breaker. Hope this helps

FYI.. the only part of the system that might use batteries is the thermostat.

if the ac outside is working, but not the furnace, means there is a control problem with the furnace, check wires in the furnace, make sure there is a blower wire plugged into the contact marked cool on the control panel of the furnace

If you have a Gas furnace in the Attic then the answer is yes. The outside condenser will not run if in fact you have a gas furnace.

When the unit does what you say does the fan motor outside stop also , if it does that means it is in defrost mode and should kick back over to normal after the system heats up the coil enough

try cleaning the burners and or adjust the distance the igniter is from the actual burner .

inside unit has fan control relay , either on control board or can be separate ,except for the 24 volt transformer and the t-stat the units operate separately concentrate totally on the inside unit this is where the problem lies