On Aug 31, 3:50 am, Uncle Monster wrote:
Telstra wrote:
"Mike" wrote in message
oups.com...
Hi everyone.

I have a central air conditioning unit in my ranch-style home (full
basement also). Yesterday the AC just kicked off randomly. I checked
the thermostat and it seemed to be functioning ok (it's digital). I
went downstairs to the power switch dedicated to the central air unit
and turned it off, then back on again. The AC kicked back on, stayed
on and started blowing cool air, then kicked back off again 2 minutes
later.

I suspected there was an airflow problem of some type (filter, etc)
but that doesn't appear to be case, at least not as far as I can
tell.

Are there any other common causes for this type of behavior?

Thank you for any responses,
Mike

There are a number of controls in series with the cooling
relay. Anti recycle timer, HP/LP control and compressor
thermal and current Overload.. However the HP control is
normally a manual reset and the LP auto reset so the Unit
as Uncle monster said is probably cycling on the LP control
which indicates a loss of refrigerant charge

It's not unusual for me and my guys to add those
controls to a contractor grade condensing unit.
I also add a head pressure control to those AC
systems installed in restaurants since the units
are run year round. If there is no electronic
thermostat with a built in anti-short cycle timer,
an inexpensive timer module installed in the
condensing unit can save an expensive compressor
from those people who like to play with thermostats.
It's often very difficult to convince some folks
to spend money on preventive maintenance.

[8~{} Uncle Monster- Hide quoted text -

- Show quoted text -

If it was low on charge, why would it kick back on and blow cold air?
If you want to be sure that it's not a control problem, remove the
face of the thermostst and install a jumper between the R,G, and Y
terminals. If the A.C. runs continually and cools effectively, replace
the t-stat.

PS: Don't worry, it's only 24volts. Be careful if there is a "C or B"
terminal that you don't touch them with the jumper as you could blow a
transformer fuse.