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'95 Escort a/c compressor - a/c switch and no refrigerant
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wa4chq
User
Feb 24, 2010, 12:01 PM
Post #1 of 3
(3370 views)
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'95 Escort a/c compressor - a/c switch and no refrigerant
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Hey all-- This is a continuation of my other posts about the a/c compressor and fan.....but the latest news and discoveries.
Well I went ahead and replaced the a/c clutch cycle switch. Turned the
car and a/c on....nothing. A buddy was there this morning and he said
to check to see if there was any refrigerant in the system. He showed
me how to do it and all that came out was air and not much of that
either. We surmise that that was from running the compressor while
being jumped. But that is the reason the a/c pressure switch wasn't
kicking the clutch in....no pressure! I took the car back to the shop
and they kept telling me the a/c won't work without the fan. I told
them that the switch won't close without pressure. If you jump the a/c
switch and the fan doesn't work why does the compressor come on? Why
doesn't my car over heat when I'm using the car? It would if it was
just sitting there but if the car is moving it keeps it cool (maybe not
the best thing to do, but it's been working like that for quite a
while) And if the a/c won't work without the fan, how did they supposedly charge the system? I'm almost thinking that they saw the
fan not coming on and they didn't charge the a/c system and then they
tell me nothing will work unless I get them to fix the fan....
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Feb 24, 2010, 1:07 PM
Post #2 of 3
(3367 views)
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Re: '95 Escort a/c compressor - a/c switch and no refrigerant
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OK: A low pressure switch in a cycling system will not allow compressor until pressure is in adequate range - usually about 40psi and would shut down in the high 20s PSI. Jumping a TWO wire LPCO switch would force it to think the pressure was always fine which is a test and a way to charge systems as sucking in new refrigerant is slow without equipment that can push it in.
True air in the system (can't tell what is there without special equipment) would be a problem as original oils used in cars made with 134a and any viscosity of PAG oils (all that I know of in 1995) the oil is hygroscopic (moisture absorbing) and turns acidic it left exposed to air and its moisture too long.
Refrigerants are VERY temp/pressure sensitive. At 40 degrees Fahrenheit the "static" pressure would be about 35 PSI if tested with a gauge and would be near exactly the same as the temp in Fahrenheit at close to 68F -- the crossing number. After 68F the pressure would be lower than the temperature.
"Static" pressure is just like checking air in a tire excepting that refrigerant pressures change so much with various temps.
A/C, 101 (like college courses) -- you can't tell how much is in the system by static pressure or even operating pressure but operating pressures, with temps all known are a way to diagnose and is telling of a low or high charge. Too little or too much isn't good. A/C want to be as close by weight as possible and the only way to know is to charge the known amount by weight into a well held vacuum. Machines or even accurate scales can measure the weight put in.
Sub note: When static pressures are below in PSI you need to know the temp. If below the known static pressure at a given temp it would mean the charge is substantially LOW!
~~~~~~~~~~~~~~
Note: The #1 reason for lack of cooling in automotive A/C is low refrigerant caused by a leak. That accounts for about 2/3rds of A/C problems - leaks! More: When forced to run or if the system runs low too long the oil doesn't move along to lubricate the compressor and will cause it to fail if too long. Too much refrigerant doesn't cool well or at all and subject to returning liquid refrigerant back to compressor to be compressed which it can't and would stall compressor or ruin it! Several failsafes are in place to prevent that, one is the LPCO switch and another is a high pressure cut out mandated for vehicles built with 134a which most model year 1993 and newer have used. Freon (brand name of R-12) is not made new by most all cooperating nations since 1993's Montreal accord. Vehicles from new list on a sticker underhood the original charge and what type of both oil and refrigerant. To date I know of no vehicles being sold to US or Canada with anything but 134a - other types are always being considered and retrofits for others available.
Again - the low switch is merely an ON/OFF switch and jumping it as with a paper clip fools the system that charge is adequate to run the system. All working items should engage as they have been fooled by that jump. Never leave a system that way but used for testing and charging only.
That is for short term only for reasons stated.
In gaseous state the common refrigerants have no natural color or harsh odor so they would seem somewhat like air,
T
(This post was edited by Tom Greenleaf on Feb 24, 2010, 1:12 PM)
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Feb 24, 2010, 1:33 PM
Post #3 of 3
(3363 views)
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Re: '95 Escort a/c compressor - a/c switch and no refrigerant
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95 Escort, all engines, listed by two sources from new were sold new with system capacity of 28 ounces of 134a and 8 ounces of PAG-#46 refrigerant oil from empty. Oil is not lost in great volume by evacuating system alone. Note: Amount of oil in the system cannot be certain without a complete flushing of whole system and starting from known zero. Component replacements or repairs along the way require good educated guessing as to how much to add depending on what was the issue.
IMPORTANT NOTE ON CHARTS: They can be wrong and will all defer to any underhood information available. Certain replacement parts will use/change system capacities usually less than any listed amounts.
When all info is unknown, charging a system requires serious attention to pressures while operating and temp measurements taken in front of condenser, output temps at center dash register(s) AND several other observations carefully noted. Always default to less than any charge weight listed when in doubt, check pressures before adding any more than about 80% as too much is both damaging and less efficient. NEVER MIX REFRIGERANTS!
T
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