Another AC Question
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Elder User
Joined: Oct 2002
Posts: 573
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From: Medina, Tn.
Another AC Question
Got a simple question for an auto AC person. On my 89 factory air with 302/ aod. Converted from 12 to R134a and I want to know about how many ounces would it hold once evacuated including oil ? Also, when do you check your pressure ? With it running and if so, for how long ?
Thanks,
Thanks,
Junior User
Joined: May 2003
Posts: 74
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From: Charlotte, NC
It should hold about 85% of the R12 rating. You have to fill it and take your readings while the truck is running and the A/C on max cooling. The capacity is on a stiker on the condenser. The R134 is mixed in the cans with the oil to the right proportions. Get a pressure gauge made for reading the pressures. They are pretty cheap or come in the kits for the conversion. Make sure your taking your reading on the low pressure side not the high side. The amount of time depends on how long it takes to get a steady pressure. Your pressure will go up or down a few points depending on the outside temp.
Senior User
Joined: Apr 2004
Posts: 443
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From: Central Va.
The capacity sticker is usally on the accumulator or evaporator case never on condensor(in front of rad).Reading hi and low pressures are a must when checking system- low or no air flow passing through condensor will show very hi readings.Check system with engine running at 1500 rpm , hi blower speed, ac on and on max. Fixed orifice system will cycle at about 26 lbs.Touch pipe where it comes out evap. case into accumulator- very short section of pipe- stinging cold to touch tells you it is cold inside (outlet of evap). Hot day depending on airflow at cond- about 30 low about 210 hi. inside temp at vent 38 to 48 degrees.Must check high side pressure (or at least know where pop-off valve is-and wear saftey glasses)
Senior User
Joined: Jun 2004
Posts: 166
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From: Yorba Linda CA
I dont normally post questions on other peoples posts but I posted a problem on my AC (88 bronco 5.0 aod tranny, stock fan) and it wont stay cold. I have replaced the compressor, the accumulator, and the orifice tube, evacuated and charged the system and still doesnt blow cold constantly. The low side shows about 30lbs - nice and steady.
I am about out of ideas, any thoughts?
I am about out of ideas, any thoughts?
Senior User
Joined: Apr 2004
Posts: 443
Likes: 1
From: Central Va.
Too much oil floods compressor-poss. Anything cold to touch? water control valve not cutting off hot water???? 92-96 temp blend door not closing all the way-Fixed quite a few- ink pens, pencils, and cigars found inside!!! (not on yours) What does hi read??? Remember TOO MUCH FREON (12 or r134a) DOES NOT MAKE IT ANY COLDER!!!!Pressures have many variables-ambient temp. eng temp. air flow in front of cond.(try spraying water on cond and see if it starts cycling- low refridge.)Bad fan clutch poss at idle-stop lights.Ideal is 38 to 48 degrees at vent.
Elder User
Joined: Apr 2002
Posts: 813
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From: NJ
pressure control switch located on the can on passenger side of vehicle. it will cut out the compressor when the pressure is to high or if it thinks the pressure is to high. they are known to stick when they go bad. i think you can replace it without loseing your freon charge.
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Senior User
Joined: Jun 2004
Posts: 166
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From: Yorba Linda CA
Thanks guys. .I will try the pressure switch, and I am not sure how much pressure the high side has.I will check the blend door and valve too. It is driving me nuts though. Cold.... warm... .Ice cold... luke warm... etc... all I want is snow blowing out of the ducts.
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Senior User
Joined: Apr 2004
Posts: 443
Likes: 1
From: Central Va.
Switch on accumulator is a LOW pressure switch -cuts compressor off at approx 28 -cuts on at approx 48 lbs of pressure( these numbers also are very close to actual temp at fitting) R134 (94 and up) have a high pressure cutoff switch( also called a containment switch), either can be removed without losing ac charge--- don't over tighten!!! I work on these all the time- been with my Ford dept since 77.
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