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Pressure too high on both low and high sides
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koolaid_kid
Novice
Jul 29, 2010, 3:54 PM
Post #1 of 13
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Pressure too high on both low and high sides
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1998 Toyota Rav4 4 cylinder, 250k miles.
Belongs to a friend, he told me the A/C quit blowing cold air last fall so he added a can of R134a, but it did not help so he stopped.
I took my gauges over there and connected them. Engine warm, ambient temp ~90 degrees. Cooling fans turned on when I turned on the A/C, compressor came on, but cycled every 10 seconds or so. Gauges showed 100/400 with compressor on. This would indicate an overcharge, however he told me he found the sight glass (I did not find it at the time) and it showed bubbles, indicating undercharge.
I can find the place it is leaking, no problem. Some Google searches indicated a clogged condensor (internally, I checked externally and it is fine). I was unable to find anything that definitely said replace condensor, could it be the orifice tube instead? He is willing to replace both, but I refuse to go into parts replacement mode. I prefer to pinpoint the problem(s) so I replace what needs to be replaced and have a working system again. He also wants to replace the o-rings while we are in there, what do you think? Of course, the receiver/dryer will be replaced, the system put on a vacuum pump, and the correct amount of refrigerant added to the system. But I prefer to do the work once, and correctly, if you know what I mean.
Thanks in advance.
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Hammer Time
Ultimate Carjunky
/ Moderator
Jul 29, 2010, 4:04 PM
Post #2 of 13
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Re: Pressure too high on both low and high sides
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No, the bubbles don't automatically mean undercharge. I wish they would eliminate those things. Thy certainly don't help. At this point it needs a complete evacuate and recharge with the exact amount of charge and then see what you have.
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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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koolaid_kid
Novice
Jul 29, 2010, 4:12 PM
Post #3 of 13
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Re: Pressure too high on both low and high sides
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Well crud. I hate to hear that. I'll get'r'dun and report the results. He is going out of town this weekend, so it will probably be a week or so before I can report back.
Thanks for the quick response.
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Hammer Time
Ultimate Carjunky
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Jul 29, 2010, 4:19 PM
Post #4 of 13
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Re: Pressure too high on both low and high sides
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You can believe a thing the pressures tell you unless you know exactly how much refrigerant is in the system.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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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koolaid_kid
Novice
Jul 29, 2010, 5:17 PM
Post #5 of 13
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Re: Pressure too high on both low and high sides
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I understand. I don't have to like it, but I understand.
I do the same thing at work, I like to have a known starting point. But like most Americans, I was hoping for a quick fix. 
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Tom Greenleaf
Ultimate Carjunky
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Jul 30, 2010, 6:14 AM
Post #6 of 13
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Re: Pressure too high on both low and high sides
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Quick fix and getting 100L - 400H suggestes wild overcharge. May have trashed that system and would shut down via high pressure cut out alone but not always in time to save it.
That mistake might just cost monster bucks.
Good luck. Start with exact known charge as Hammer Time said and diagnose from there if not cooling properly.
Sight glass is not dependable for 134a. If there's one at all and there are some usually on X valve systems not CCOT systems ever that I've seen and would be on a reciever drier or closeby,
T
(This post was edited by Tom Greenleaf on Jul 30, 2010, 6:18 AM)
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koolaid_kid
Novice
Jul 30, 2010, 6:42 AM
Post #7 of 13
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Re: Pressure too high on both low and high sides
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Thanks. He told me the sight glass is on the drier. He has priced out the components (drier, o-rings, condensor, hoses, evaporator, orifice tube, etc.) and sounds willing to replace anything and everything required. He has not priced the compressor, but IDK that it has failed since it is still compressing.
The biggest cost IMHO is labor, and it is virtually free. He does bike work for me, and I do car work for him. A good tradeoff as far as I am concerned.
The only bad thing is that he tends to replace parts until things work. I tend to diagnose until I understand root cause, which takes longer but is cheaper in the long run.
I still don't understand one thing: Why did it fail in the first place? If adding one can of refrigerant caused such a massive overcharge, what happened to begin with to make it stop cooling? I hope to dig into it next week, this will be interesting.
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Tom Greenleaf
Ultimate Carjunky
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Jul 30, 2010, 6:57 AM
Post #8 of 13
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Re: Pressure too high on both low and high sides
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There's no "O" tube TMK in this system!
Quote ">>The biggest cost IMHO is labor<<"
No - the biggest cost is mistakes. It doesn compress but the high suction suggests way too much refrigerant for now. Systems don't hold 5-6 POUNDS like way back when so a single pure can of 134a can take one from too low to way to high and neither are good.
Suction should hover around high 20sF and high side around 2.2 +/- the temp in Fahrenheit of air entering condenser. That would mean at 90F entering you might see about 200 high not 400 - yikes! All this with raised idle and fans working properly and system set on max cooling.
Performance will show it's real colors when really driving the thing - not just sitting there,
T
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koolaid_kid
Novice
Jul 30, 2010, 3:23 PM
Post #9 of 13
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Re: Pressure too high on both low and high sides
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It has an expansion valve, which performs the same function as an "otube".
I can at least agree with the YIKES. We will see.
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koolaid_kid
Novice
Jul 30, 2010, 4:07 PM
Post #11 of 13
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Re: Pressure too high on both low and high sides
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I could not agree more. Last year, I found out he was throwing parts at an engine performance issue on his Corolla. Lots and lots of parts. I put AutoTap on his OBDII port to collect and analyze data, and my LM1 in his exhaust. Diagnosed it as bad injectors and a bad front O2 sensor. He replaced the sensor, sent the injectors to be rebuilt, and has been pleased as punch ever since. Spent perhaps $100 total, less than 20% of what he had already wasted in not fixing the problems.
I would rather spend 3 times as much effort in diagnosis and save money and effort in parts replacement.
What most people do not realize is that there is almost always more than one issue. It is like peeling away the layers of an onion. Until you peel away the upper layers, you cannot see the issues that lay beneath.
The really odd part is that he is a whiz on Suzuki GS motorcycles. He has fixed so many issues with mine and others that it is amazing. But when it comes to cages, he is clueless. You never know, I guess.
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Tom Greenleaf
Ultimate Carjunky
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Jul 30, 2010, 7:10 PM
Post #12 of 13
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Re:98 Rav4 - Pressures too high on both low and high sides
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Just FYI: 98 Rav4 only holds 25 ounces of 134a. Pure product little cans hold 12 oz. Some snake oil kits hold 18 or more of 134a and junk. If 12 oz went in that's close to double the charge and it isn't known if low charge was the problem at all. More is not better and too full won't cool at all. A/C is physics not a parts toss,
T
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koolaid_kid
Novice
Jul 30, 2010, 7:26 PM
Post #13 of 13
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Re: Re:98 Rav4 - Pressures too high on both low and high sides
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Thanks Tom. I'll keep that in mind.
My friend is a web designer, not an engineer, so there is no way knowing what he did.
George
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