On Thursday, June 19, 2014 8:25:22 AM UTC-4, jamesgang wrote:
On Thursday, June 19, 2014 7:50:37 AM UTC-4, Davej wrote:

On Thursday, June 19, 2014 6:39:38 AM UTC-5, trader_4 wrote:



On Wednesday, June 18, 2014 10:16:26 PM UTC-4, Davej wrote:







So the compressor runs and then at some point the A/C



decides to turn on the blower fan. Mine works fine for



awhile, but then it starts turning the fan on and then



off again, within a few seconds, as if it can't decide



whether the coil is cold enough.











Are we talking about a central AC system that's part of



a furnace?







Yes







IDK what the latter does, but in all the first two types



that I've seen, the coil temp doesn't control the blower.



The blower is turned on and the compressor start at the



same time. When it shuts off, the blower typically stays



on for another minute or two after the compressor goes



off.











Hmmm, you're right. I thought it worked identical to the furnace but apparently not. I've had this strange blower fan operation ever since the furnace was installed and have used continuous fan to avoid it, but now even continuous fan has strange behavior.



You need to put a meter on it and see if it's getting power but not running or if the control board is not keeping it powered.

Agree, that would be a good place to start. Also, if it;s a modern unit,
they have LEDs that light to indicate OK or identify faults if the CPU
board knows there is one.

Running the fan constantly may not be such a good idea either. In furnaces
from 25 years ago, putting the fan on all the time put it on high, the
same speed as for cooling. Which is OK, except that those motors were
not efficient and it's going to run up $$$, running when it doesn't need to..

Newer furnaces, the blower when set to run all the time, doesn't run
at high speed. Mine runs closer to the heating speed. That isn't going
to produce maximum cooling. With mine, if the AC kicks on, then it goes
up to high. With the OP system with the problem, without knowing how
it operates no way to know what it does.