It is normal for the A/C to cycle on and off unless the temperature is
quite high. In warm weather it typically have a higher duty cycle in
"Fresh" than "Recirk". (Opposite if using the A/C in cool weather e.g.
to defog).

The cycling is controlled by the thermostat mounted in the evaporator
housing. Specifically, the ECM controls the A/C compressor clutch relay
based on a call for cooling. The call for cooling gets to the ECM
through (in order from ECM to ground) 1.) the A/C pressure switch in one
of the refrigerant lines, 2.) The A/C thermostat in the evaporator
housing, 3.) the A/C main on/off switch on the dash and 4.) the
ventilation fan switch on the dash (separate pin grounded with fan
switch in any position except off). The A/C pressure switch is a
safety-lockout. This switch is normally on at all times.

>From my home central A/C I know that too much refrigerant will reduce
the cooling capacity of the A/C system. Perhaps you overcharged the
system, have reduced cooling capacity and thus the evaporator never gets
cold enough to turn off the compressor? Measuring only the low-pressure
side is somewhat dubious. For proper charge, filling to a specific
pressure is not sufficient, the correct pressures (high and low side)
depend heavily on outside temperature *and* humidity. Since R134a is
cheap I would try removing some refrigerant (observing all relevant
environmental regulations, precautions and safeguards) and see if that
helps.


Andrew McCune wrote:
>
> I just added refrigerant to my 1995 Prelude SE (125,000 miles), and noticed
> both while I was recharging and after that the compressor doesn't cycle off.
> Is it normal for Honda compressors to run full-time (while the "A/C" button
> is on)? I can't specifically remember if it cycled during the years I've
> owned it. If it SHOULD be cycling, what would prevent it from doing so?
> Using the manual "A/C" button on the console does cause the compressor to
> turn off, as normal. One item to note, is that I used one of those
> inexpensive "system recharge" packages from the auto parts store to add
> refrigerant, which seemed to work well, but it only measures low-side
> pressure. Thanks for your help.