Re: AC Problem - lines froze
"Michael Pardee" <firstname.lastname@example.org> wrote in message
> "James Sweet" <email@example.com> wrote in message
> > "Michael Pardee" <firstname.lastname@example.org> wrote in message
> > news:HKSdnePQf7dsfqPeRVn-tA@sedona.net...
> >> "TEC" <email@example.com> wrote in message
> >> news:firstname.lastname@example.org...
> >> > Situation where if AC on low fan, both the high pressure and low
> >> > pressure lines froze - frost on both lines. Pretty soon, blowing warm
> >> > air only. Fan on high, not a problem.
> >> >
> >> > Also compressor seemed to fail to cycle, running all the time, and
> >> > mileage dropped badly.
> >> >
> >> > How do Volvo's control the clutch and cycling of the compressor?
> >> >
> >> > Thanks
> >> >
> >> We really need to know model/year on this, and if the year is earlier
> >> than
> >> about 93 whether the system has been converted to R134a. Something that
> >> strikes me is "frost on the high pressure line." Is this the line from
> >> the
> >> condensor, past the valve, where it enters the evaporator? (If not, I'm
> >> lost.)
> >> Mike
> > High pressure line = liquid line = the line from the compressor to the
> > orifice tube or expansion valve.
> That's what doesn't figure. That part should be hot under all conditions
> (except compressor off). The section from the valve to the evaporator can
> cooled to frost by flash gas if the system is running full bore. To that
> extent, I think the OP was doing the best by focusing on why the
> was always engaged.
Er, I forgot to mention the condenser in there, the line goes from the
compressor to the condenser, and then to the expansion device. The line
between the condenser and expansion device shouldn't be hot, but it should
be a bit warmer than ambient depending on condenser efficiency. If that line
is iced up it can be one of two things, a kink or blockage causing a
pressure drop and some of the refrigerant to boil off in the line rather
than in the evaporator, or the evaporator can be so iced up that the liquid
line ices up nearby just from conduction.