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Old 07-20-2011, 01:06 AM   #1
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A/C help, high side pressure 450psi

I have a '94 3.8L that I use as a daily driver. Over the last 4 years I have had to add a 12oz can of 134A every spring. This year it wouldn't take, the pump would run for a couple seconds then turn off for couple then repeat. I took it in to have a professional take a look. He said that the high side pressure was too high at 450psi. This was on a 85 degree day. He recommended replacing the condenser, he thought it might be plugged or restricting flow. He quoted me $300 for the repair.

I don't know much about a/c work. I know how it works, that's about it. Anyone else have any thoughts? I found a condenser online for $45 including free shipping. And a local shop said they could vacume and charge for $65. I thought I would try asking a few questions on here before I start throwing parts at it..
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Old 07-20-2011, 01:41 AM   #2
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Prussures that high are indicative of a restriction or insufficient air flow across the condensor which could be from a bad fan or the condensor being plugged with crap.
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Old 07-20-2011, 01:45 AM   #3
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Quote:
Originally Posted by gnvair View Post
Prussures that high are indicative of a restriction or insufficient air flow across the condensor which could be from a bad fan or the condensor being plugged with crap.
What can get into the system to plug it? Could there be larger problems I should be worried about? Or should I throw a condenser at it?
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Old 07-20-2011, 02:02 AM   #4
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Quote:
Originally Posted by zbantam View Post
What can get into the system to plug it? Could there be larger problems I should be worried about? Or should I throw a condenser at it?
The thing is that if you have a restriction in the system it is usually a result of the compressor coming apart. In rare instances the dessicant bag in the accumulator. They usually start to plug the orifice tube. The only way to know is to cut open the line from the evap to the condensor. There is a crimp in the middle that retains the orifice tube. If there is metal on it then you know the compressor is done. I would start with easy things such as making sure the fan is working. If you have a stock clutch fan, make sure the clutch is engaged when hot. Sometimes they fail and the fan spins, but not like it should.
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Old 07-20-2011, 08:45 AM   #5
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Quote:
Originally Posted by gnvair View Post
The thing is that if you have a restriction in the system it is usually a result of the compressor coming apart. In rare instances the dessicant bag in the accumulator. They usually start to plug the orifice tube. The only way to know is to cut open the line from the evap to the condensor. There is a crimp in the middle that retains the orifice tube. If there is metal on it then you know the compressor is done. I would start with easy things such as making sure the fan is working. If you have a stock clutch fan, make sure the clutch is engaged when hot. Sometimes they fail and the fan spins, but not like it should.
450psi indicates that the pump is good right? I swapped in a mechanical fan from a '89 when the electrical fan quit on my. I will check the clutch when I get a chance.

Thanks for your help.
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Old 07-20-2011, 08:50 AM   #6
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Quote:
Originally Posted by zbantam View Post
450psi indicates that the pump is good right? I swapped in a mechanical fan from a '89 when the electrical fan quit on my. I will check the clutch when I get a chance.

Thanks for your help.
A compressor can still make pressure and still be failing.
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Old 07-20-2011, 09:31 AM   #7
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Orifice tube also may be the problem.
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Old 07-20-2011, 11:24 AM   #8
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Orifice tube also may be the problem.
Usually the orifice tube (as I previously noted) can become the restriction when the compressor comes apart.
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Old 07-20-2011, 07:13 PM   #9
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Moisture in the system will cause high side pressure to become higher than normal.
too much oil in the system will cause it too.
So will that leak detector crap.
And leak "fix" garbage is a guaranteed compressor failure waiting to happen.
Lack of airflow across the condenser core will cause high pressure.
And clogged or bent up condenser fins will add to lack of airflow.

So if the tech doing the checking didn't have a fan in front of the car while checking, chances are good that the high side pressure is high. Need to simulate driving conditions (1500-1800 RPM, fan in front of car).

If you've been charging every year, what refrigerant were you using? Hopefully straight R134A without that "other garbage" in it (including oil).

have seen lots of cars...my truck included...that need to be charged about once a year. Most of them the compressor seal starts to leak slowly. About once a year usually it needs to be charged. Dad used to charge his once a year and was using that leak fix crap. Doesn't do a thing but plug the system up. I will say this. It's far cheaper in the long run to fix the source of the leak than it is to recharge it every so often. At the very least, you're going to want to have the system evacuated, then remove a line and inspect it for any residue. Shouldn't be anything but clear oil film. Then fix the source of the leak wherever it is. Then replace the accumulator/dryer. Then pull the system into at least 29" of vacuum and let it sit overnight. Check the next day to see if it's the same exact vacuum reading...or really close (temp changes can affect the actual vacuum). If all is good, start the engine and let it get up to operating temp, then vacuum it again for at least 30 minutes while the engine is hot. This gets ALL the moisture out of the system. Now it's time to charge. Fan in front of the car on high, engine at idle speed initially. Once the first can is in, you can increase the idle to 1500-1800 RPM and continue to fill the system. You'll want 20-30 psi on the low side and 275-300 on the high side. If the fan isn't real strong the high side will go higher...mine is 350 psi unless I get the BIG fan out (don't ask...3 phase industrial ventilation fan that blows away everything not bolted down within 30').

That's the way I've always done it. I do all my own A/C work for the most part unless I'm too lazy to pull the dash to fix an evap leak or something like that. Not rocket science but you need to know what you are doing and use lots of thought into what you're about to do. The tools are expensive too. I bought a Matco 2 stage vacuum pump (I also use it at work occasionally) and a Matco digital manifold gauge set. That's it. That was close to $650 for those two items, not counting the fittings, adapters, vacuum pump oil, and the other little tidbits that ya might need. One thing to note is that when hooking up the gauges, before charging it's a good idea to purge the lines to get the air/moisture out if there is any. Also the oil needs to be added to the system BEFORE buttoning it up..don't use that 134a with oil crap. Some do and get away with it but if you're going to do it properly, do it right once and worry not later.

There's lots of shortcuts that can be taken but they all add up to sub par operation of the entire A/C system. And...if you're really lucky, compressor failure.
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Old 07-20-2011, 10:03 PM   #10
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Todd,

I have been adding a can of 134a with leak fixer and or oil. Whatever is on sale. Which is usually the leak seal crap. I didnt think about it but i bet i have about 4 or 5 cans in that system.

I wish i could do my own work but i dont know much about a/c. I can rebuild a trans, setup a rearend or build an engine but i have stayed away from a/c work.
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Old 07-21-2011, 01:19 PM   #11
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Quote:
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Todd,

I have been adding a can of 134a with leak fixer and or oil. Whatever is on sale. Which is usually the leak seal crap. I didnt think about it but i bet i have about 4 or 5 cans in that system.

I wish i could do my own work but i dont know much about a/c. I can rebuild a trans, setup a rearend or build an engine but i have stayed away from a/c work.


It can be done at home. You can pick up a used manifold gauge set for around $50 if you look around (heck I've seen new ones for that). The vacuum pump can be bought for $100 as well..or less if you get a pneumatic one, but be prepared...the pneumatic pumps need a GOOD compressor (lots of CFM). Or build one out of an old junkyard refrigerator compressor. Info for that is all over the 'net.

Vacuuming the system is probably the 2nd most important part. What you're doing is removing the moisture. Water boils at 212 deg at seal level, which is somewhere around 14.5 psi actual pressure. We don't notice it because we're used to it. If you pull the system into a vacuum of around 29" of mercury, water will BOIL at around 50 degrees F if memory serves me correctly (chart not in front of me). When it boils, it is removed from the system and therefore the system will work as it's designed to. Moisture in the system will cause compressor to work harder, also causes corrosion and reduced cooling ultimately.

Need to get all the original stuff out. Usually flushing is best. The flush stuff can be bought at the parts stores. You'll also want a new accumulator for sure. Usually comes as part of the hose assembly. If the condensor is dinged up, it's cheap to replace as well. Usually around $100 give or take new. Most expensive part is the compressor. Good to replace it. But as long as there's no metal in the system it might be salvageable.

You'll want to have the system recovered. Most places don't charge much for it. They're just removing the 134a that's in it. It can be done at home as well but how you go about doing it is your business. From there, just as matter of replacing defective or broken parts. Then flush. Then vacuum to check for leaks. Then add oil to the system once it's leak proof. Then start the engine, put some heat in it and then vacuum it down one last time before adding refrigerant.

A/C work at a repair shop is expensive. Why? Lots of overhead. Tools especially. Recovery units are $2500-$10,000 depending on what kind they are and what they do. Every A/C repair has a little bit of $$$ built into it to help pay for the tools. Then labor. If a tech has to replace an evaporator it's not cheap (long job). If you have the time and a couple of the main tools, it can be done in your garage for 1/10 of what a shop charges. Fixed my '93 LX 4 years ago (was originally R12, o-ring failed & leaked it out)...R&R'd the accumulator, o-rings, flushed it all out, replaced compressor with a JY unit and recharged for around $100 total. Labor was free because I did it. I did buy the gauge set and vacuum pump though and that was a chunk of change but I use it at work too (tractors) so it's more or less paid for. I still need to buy/make some sort of recovery unit...but most of the stuff I've worked with has already leaked the refrigerant out totally and those that haven't are repairable without opening the system...so far. Had 2 or 3 that needed recovered but we had a mobile a/c repair guy do that for free. We just let him have the refrigerant. If it's R12, they'll pay us for it.
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Old 07-22-2011, 01:33 AM   #12
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You have non-condensibles in the system, probably from not purging the charge line every time you topped off, besides you have not weighed in the correct charge.

You cannot just top off without knowing how much has leaked, ITS critically charged.
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Old 07-22-2011, 08:33 AM   #13
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The shop i took the car too, pulled the system down and charged it correctly and reported a 450psi high side pressure. Then stated that i needed a condenser. They quoted me $300 for the job. The guy is a family friend and i trust him, i just didnt have $300 to spend at the time. i figured i could save a couple bucks and pickup a condenser and put it in myself then have him charge the system. I have found condensers for as low as $45 at radiatorwarehouse.com they also have an ebay store.
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Old 07-22-2011, 09:17 AM   #14
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garden hose or shop air can quickly unplug the condenser.
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Old 07-22-2011, 12:16 PM   #15
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Good info on here Todd
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Old 07-22-2011, 12:55 PM   #16
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^ ya for realz! Thanks Todd
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Old 07-22-2011, 06:43 PM   #17
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Is there a way to test the condenser? I hadn't thought about clearing the lines. If I get time this weekend I will fire up the air compressor.
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Old 07-22-2011, 11:39 PM   #18
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the condenser not the lines.
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