Re: More a/c questions

["content22207" <brobertson@xxxx>]

Don't know R12 static pressure (R134 is 90 - 100 PSI), but tech manual
N:05:01 STARTS at 60 PSI. Would imagine anything less trips low
pressure switch as soon as cycle starts. Take it back at least to 60
PSI then begin diagnosis.

High and low side pressures are on page N:06:01 (or page N:09:01).
Remember: A/C can appear backwards -- high side reading too LOW means
system is clogged (most people think opposite simply because it's
pumping there. Actually no way compressor alone could emulate physics
of refrigeration. In fact, have been told heart of whole operation is
suction, not output). You need a good cycle to get into 200 plus PSI
range. When everything's clear you should see low side drop and high
side climb (hence the names). 

BTW: This is one reason I do most of my work on low side. Reading too
high -- system is clogged (hot air from vents) or overcharged (cold
air from vents). Too low -- freon is low (assuming PSI drop has
occurred). Makes more sense. Plus on a 134 conversion most people just
put quick connect on low side only.

RE: compressor cycling -- under optimal conditions it is NOT supposed
to cycle. Note on page N:01:01 that cycling is response to frozen
evaporator (blocked by ice -- remember clogged high side LOWERS
pressure). If system is clear, freon level correct, and DeLo sitting
in the sun, compressor should run continuously. Cycling compressor
means something's wrong.

BTW David T: thought some more about iced up evaporator on my Two Tone
Lincoln last year. Ford's freon metering device ("throttle suctioning
valve") has no compressor shut off feature. Does have an orifice
bypass line, but that's usually triggered by a stuck expansion valve
(WAY too much freon). My conversions are probably splitting the
difference -- too much freon into evaporator due to higher R134
pressures psyching out TSV, but not enough to open bypass circuit.
Only getting away with it by passive heat radiating from heater core
and continuously melting ice (is only separated by a plastic door).
Remember: froze up when heater core was bypassed due to leak. Hasn't
frozen since.

Same principle must apply to my DeLo. If it isn't passive heat from
heater core (good reason to use "Norm" setting vs "Max"), may be
because interior absorbs so much sun!

Bill Robertson
#5939

>--- In dmcnews@xxxxxxxxxxxxxxx, "geek123y" <ken@xxxx> wrote:
> List :Members
> My car had loss of R12 the compressor stopped and wouldn't come on I 
> added 1 pound of R12 and some die and ran it for a week it was a slow 
> leak at the condesor fitting