Central A/C fan keeps turning on and off after it's been on for a while

[greent]

I've noticed for the past month if I've had the A/C on for a while (let's say overnight or half a day or so), the A/C will start up then shut off 5 sec letter then turn on 10 sec later then shut off.... like 4-5 cycles before I get annoyed with it and turn it off. I didn't think much of it at first cause this usually happens in the morning when I'm half asleep, so I just shut off the Cool and Fan and go back to sleep. However, I've noticed now during the day after I've had it running for 5 hours or so it starts to do this.

The last time this happened I shut off the Cool and left the Fan on and it was still doing the on/off thing, which makes me think it's the fan?? Also, we just had our Frion and pressure checked recently (2 months ago) and they said it was good. Also changed the filter about a month ago.

Any thoughts? Thanks in advance!

[HayZee518]

A/c

why would you think its the fan? the fan starts because of some other device. the whole system gets its start from the thermostat.
if the stat is registering ok, then its the peripherals in between the contactors and compressor.
is there a high pressure limit or a low pressure limit?
you changed the filter. how is that gonna affect anything unless you have an air flow switch that is just flopping around in the breeze.
a heat/cool anticipator can be at fault.
loss of freon would cause no cooling whatsoever

[greent]

why would you think its the fan? the fan starts because of some other device. the whole system gets its start from the thermostat.
if the stat is registering ok, then its the peripherals in between the contactors and compressor.
is there a high pressure limit or a low pressure limit?
you changed the filter. how is that gonna affect anything unless you have an air flow switch that is just flopping around in the breeze.
a heat/cool anticipator can be at fault.
loss of freon would cause no cooling whatsoever

I think it's the fan because when just the fan is on I hear the same thing -- it turns on then off then on then off. So I guess the problem really is with just the fan and not the A/C. Mind it'll run fine for a while (sometimes an hour, sometimes a few) and then it does the on off on off thing.

I only preemptively mentioned the filter because I feel like I always get asked that when there's an A/C problem. Sorry if it offended. I guess I'll just call someone.

[HayZee518]

fan etc

no don't be offended. I was just trying to eliminated just another problem. some units have an air switch that uses a vane connected to a microswitch that is part of a control circuit.
and you said the fan goes on - off, on - off. there's something that turns on the fan.
the condenser fan comes on when there is latent heat that needs to be removed from the condenser.
the condenser cools down the freon so it can be used to remove room heat from your room.
lemme ask you this - do you know the refrigeration cycle in a unit?
on your compressor you have a larger copper line and a small line. the larger is what they call the suction line, the smaller is the high side or high pressure.
a liquid cannot be compressed, a gas, yes.
so you have high pressure gas coming out the compressor at a high temperature. this gas must be cooled down if it is to remove room latent heat so it is sent to the condenser coil where it is cooled. after the condenser the freon travels to the evaporator where the coolness happens. the high pressure gas flows across an orifice where there is a pressure drop. the cooled gas turns back into a liquid which absorbs heat and goes back to the compressor to be recycled.
there must be a thermostat which powers the condenser fan motor. On a room a/c unit there is a double shaft motor. one side powers the evaporator fan, the other side powers a condenser fan.

[HayZee518]

a/c

if you can snap a picture of the schematic diagram of the whole control circuit. we'll figure out what is short cycling your system.