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Not sure about evacuating the AC on my 1994 toyota pickup
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masondog
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Jun 1, 2010, 3:26 PM
Post #1 of 15
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Not sure about evacuating the AC on my 1994 toyota pickup
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OK , so far so good. I rented a little mastercool 1.5 cfm pump to evac my system. It pulls down to -22 in a few minutes and then gets it to -25 after about five minutes and thats as far as it will pull it after 30 minutes. I turned it off and checked the gauges after another 30 minutes and it holds the vacuum but is -25 enough and if it pulls it down to that number in just five minutes does that mean the pump is to small?
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Hammer Time
Ultimate Carjunky
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Jun 1, 2010, 3:44 PM
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Re: Not sure about evacuating the AC on my 1994 toyota pickup
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No it is not. That will raise the boiling point too much and you won't accomplish anything with the vacuum. See if it will pull 29 on the gauges themselves without being attached to the car. Low vacuum like that usually means a leak but it may be just a weak pump. It's always possible that your gauges are wrong too and it really is pulling more.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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masondog
Novice
Jun 1, 2010, 6:57 PM
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Re: Not sure about evacuating the AC on my 1994 toyota pickup
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Good thinking. I put the vacuum on just the gauges and it pulled down the same mm Hg. So I thought that maybe the pump was very efficient and that I just need to be patient and let it purge. So then I go to put R134a in and immediately I hear a hiss out the fittings on the dryer. Then I thought I should have got the OEM sized O-rings instead of estimating the size which I will do next. But I'm telling you it held a vacuum.
Question: Can I put air pressure on the system and use soap bubbles to look for leaks? At least I will save refrigerant and time. PS. This forum is the best on the web.
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Hammer Time
Ultimate Carjunky
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Jun 1, 2010, 7:00 PM
Post #4 of 15
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Re: Not sure about evacuating the AC on my 1994 toyota pickup
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An old trick we used to use when you couldn't vent at all was to leave fumes in the system and pressurize it with air and use a leak detector. You can try the soapy water but it would have to be a pretty big leak to show up that way.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Tom Greenleaf
Ultimate Carjunky
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Jun 1, 2010, 9:37 PM
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Re: Not sure about evacuating the AC on my 1994 toyota pickup
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Quick note: Vacuum at sea level is 29.92 Hg. Can be adjusted about 1 Hg per 1,000 feet of elevation. 25 Hg. would be all you would see if at 5,000 ft. Size of the pump isn't an issue just faster to get to the same vacuum with stronger ones. Change oil in pump may help,
T
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masondog
Novice
Jun 2, 2010, 11:27 PM
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Re: Not sure about evacuating the AC on my 1994 toyota pickup
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OK. now I began to charge the system. Started the engine as well. I put in about two thirds of a 12 oz.can. The system is at about 75 psi with the engine running but it shows 75 psi on both the high side and the low side. My original problem was intermittent cooling with the system running about 120 to 150 on both sides which was supposed to be indicative of either a clogged expansion valve or a bad compressor. So with the expansion valve replaced I guess I am looking at a new compressor.
Question: Is the two thirds of a can in the system at 75 psi enough to assume the lack of a high side / low side pressure differential is not going get any better? or should I charge it all the way up and see?
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Hammer Time
Ultimate Carjunky
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Jun 3, 2010, 2:45 AM
Post #7 of 15
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Re: Not sure about evacuating the AC on my 1994 toyota pickup
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The big question is, is the compressor even running. If it is, then yes it's fried and not pumping anything.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Tom Greenleaf
Ultimate Carjunky
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Jun 3, 2010, 6:09 AM
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Re: Not sure about evacuating the AC on my 1994 toyota pickup
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">>About 2/3rds of a can<<"
A/C isn't 'about' - ABOUTs. Weigh the cans. If you don't have a scale to fractions of ounces you are wasting your time and risking big bucks.
As HT said -"Was compressor even running?" otherwise it's just a static reading which is pretty exact in relationship to temp IF pure refrigerant.
Chart here:
http://autoforums.carjunky.com/...Chart_-_134a_P59651/
That link and others locked up top of this section are just a scratch in what you need to know to properly charge a system.
Know all your temps - not the one hanging on a tree - the real temps under the hood and in front of condenser, compressor engaged, raised RPMs, fan(s) known working properly and more.
What is your altitude? What is the humidity? Have you purged lines on gauge set of air? Doesn't take much air to mess up the whole show. Remember - a perfect vacuum is really ZERO. We live in 17.6 PSI of pressure at sea level so we think of that as the zero mark but it isn't. There's water in air big time and if in the A/C system it will/can create unseen frost right where it shouldn't and all numbers are screwed.
Regulars are here to help but you need the basics known or target the inquiry as best you can with what has been noted,
T
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masondog
Novice
Jun 3, 2010, 9:46 AM
Post #9 of 15
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Re: Not sure about evacuating the AC on my 1994 toyota pickup
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Ok, you are right about the temps so I think I will get a good AC tech thermometer. Humidity though I will have to get another instrument for that.
However, I neglected to say that all along the comp. would kick in and I could see the clutch engage and hear the engine draw down from the comp. load. I tested the pressure at idle and at 2000 rpm and the pressure gauge reading did not change and stayed at approx. 75 psi , high and low side, which was what it was doing before I replaced the expan. valve at 150 psi..
Now I already pulled the comp. and the pulley feels smooth , with slight end play. When I turn the comp. by hand I can hear the pump gurggle like it is pulling vacuum.
Question; Can I have the compressor tested anywhere now that I have it out of the truck ?
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Tom Greenleaf
Ultimate Carjunky
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Jun 3, 2010, 10:25 AM
Post #10 of 15
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Re: Not sure about evacuating the AC on my 1994 toyota pickup
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OK: If with some of anything in the system and compressor engaged the 75 low side reading staying the same at both off, idle and 2,000 RPM strongly suggests it can't do squat. At first when charging by cans you can even see the pressure of low going into vacuum on it's own suction normally.
Without equipment (big bucks) that simply puts in by force the correct weight of charge it's the system drawing it in. Your small can will quickly get cold - again the represents loss of pressure which is stupid - pressure will travel from the higher to the lower of the two.
Humidity you can usually feel. It can effect performance of the system day by day but shouldn't get in the way of charging it. A cold day like below 60F can be troublesome to charge a system and check performance. We don't dial the weather but it's nice to work when 80 to 90F.
No matter. This pump from what I'm seeing into this just can't pump. It's just splashing inside with some oil now.
Do yourself a favor and seal off open ends of system now that compressor is off. Air gets in the rest of it and the PAG oils and the desiccant in driers will overload with moisture. PAG oils can become acidic with moisture and wreck other parts faster later so it can't be left exposed.
For thermometers I have all sorts. Like plain wired in/out ones for home or car ones that cost about $10 bucks. You just switch to see performance out vents and back to air temp entering with same unit.
X valves have a bad history even new ones. But no change in low pressure while engaged is quite damning for a lousy compressor.
Measure the oil you can get out of it now. Don't re-use oil but note how much and the condition. If full of junk or blackened this job has gone major. Doesn't take a teaspoon of debris to kill a system,
T
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masondog
Novice
Jun 3, 2010, 5:02 PM
Post #11 of 15
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Re: Not sure about evacuating the AC on my 1994 toyota pickup
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Since getting the refrigerant right by weight is not only critical but probably necessary for optimum cooling and I live in Phoenix. I think I will find a reliable AC garage to charge it up. I got a new Nipon OEM compressor for after market price so I am pretty happy.
Question: I am putting in the PAG oil. I dumped out the shipping oil. The counter guy said the system calls for 7 oz. So I'm supposed to put 4 in the comp , 1oz in the dryer and 2oz in the lines. Does putting that much oil , 1oz., in the dryer sound right to you?
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Hammer Time
Ultimate Carjunky
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Jun 3, 2010, 5:32 PM
Post #12 of 15
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Re: Not sure about evacuating the AC on my 1994 toyota pickup
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What about the old oil still in the system? Are you counting that?
I wouldn't put any more than 4 or 5 in there, 6 or 7 if you flush or replace the compressor as you should be doing..
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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masondog
Novice
Jun 3, 2010, 5:59 PM
Post #13 of 15
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Re: Not sure about evacuating the AC on my 1994 toyota pickup
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I flushed the condensor. evap, and the lines with PAG 46 and compressed air and I think most of it is out. The condensor might have a little because it is serpentine but I angled it around while shooting air through it.
You know what I am not to sure about taking it out to someone. I just called a referal from the parts guy and he doesn't have a scale. My inner voice says " I can buy a digital postage scale and get the weight easily with in the manufac. 1.21 min / 1.43 max.. The first can I can empty out and then subtract that from the next can and get it right on. Tell me if I'm wrong on this?
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Hammer Time
Ultimate Carjunky
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Jun 3, 2010, 6:05 PM
Post #14 of 15
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Re: Not sure about evacuating the AC on my 1994 toyota pickup
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Charging is not a big deal as long as you can pull a good vacuum on it first and get the right amount of refrigerant in it. Make sure you spin the compressor by hand about 10 revs after it's installed to purge the oil out of it so it doesn't hydro lock on the oil when it fires up. If you charge it with 12 0z cans, you can count out the right charge.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Tom Greenleaf
Ultimate Carjunky
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Jun 4, 2010, 8:49 AM
Post #15 of 15
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Re: Not sure about evacuating the AC on my 1994 toyota pickup
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">>Since getting the refrigerant right by weight is not only critical but probably necessary for optimum cooling and I live in Phoenix.<<"
Understood! Phoenix w/o A/C would be like no heat in Winter for me.
Need help? Lives and owns a store for A/C equipment in Phoenix.
Warren W. Ph: 602-595-6430(store #)
Sells to the trade mostly but would know who's who in Phoenix for sure.
T
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