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Is there a way to test an AC compressor?

lv6l on Fri August 01, 2008 6:05 PM User is offline

Year: 1994
Make: honda
Model: civic
Engine Size: 1.6
Refrigerant Type: r134a
Ambient Temp: 80
Country of Origin: United States

I have two compressor, one in my car currently and one in my garage. My AC system is not getting cold on hot days. It will also not get cold if I sit my car at an idle. It will only get cold from constant driving, I'm suspecting it's my compressor that has gone weak. I want to know is there a way to test a compressor. I would like to install the other compressor I have in my garage but do not know if it's still good because it has been sitting there for a while. Thanks.

CyFi on Fri August 01, 2008 6:51 PM User is offline

best way is to hook up a gauge set to the car and check pressures, it will give you an idea of how the system is performing.

Chick on Fri August 01, 2008 7:13 PM User is offlineView users profile

Not sure, but you may have a sight glass, if it's properly charged the sught glass should be clear with no bubbles..As I said, I'm not sure if your car has one but check first, also pressures are needed..

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

TRB on Fri August 01, 2008 7:43 PM User is offlineView users profile

Check the tips forum. I think there is a procedure for this or at least a way to check if the pump is working to some degree.

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Edited: Fri August 01, 2008 at 7:43 PM by TRB

webbch on Fri August 01, 2008 7:47 PM User is offlineView users profile

As mentioned, not the right way to diagnose the problem at all. Get yourself a manifold gauge set from ackits.com and check the low and high side pressures at 1500 RPM while monitoring both the ambient and vent temperatures before even THINKING about condemning the compressor. Could be a LOT of other reasons for your lack of cooling.

That said, there is a compressor testing procedure in the FAQ section, but not sure it applies to your type of compressor or not.

Chad

lv6l on Sat August 02, 2008 4:16 AM User is offline

I have an AC manifold gauge. I did plug it in and test the pressure, from using the formula 2.2-2.4 X ambient tempurature I got a reading that is very low on the high side. I forgot the exact numbers but it was something like 80F outside, so 80x2.2=176. My high side gauge was showing nowhere near there, it was barely hitting 120ish. And low side was at 35. But this is at idle, I will do another test tomorrow with engine at idle, 1500rpm rev, and for sure when I rev it higher than 2000rpm it will start building good high side pressure. From this that is why I thought my compressor is getting weak. But I will take another test tomorrow and let you guys know.

Also, I do have a glass on my drier and I do not see any bubbles or anything. Clear as a whistle.

Edited: Sat August 02, 2008 at 4:19 AM by lv6l

NickD on Sat August 02, 2008 10:29 AM User is offline

Referring to bench testing I assume, does take a bit of effort to install it, add lubricant, draw a vacuum, charge only to learn it doesn't work.

First thing to learn is can you hand turn the compressor and should feel very smooth with no rough spots over several full rotations.

A compressor is a unidirectional pump that must have good compression with very little leak back showing that the rings are good as well as the reed valves are sealing. A high pressure gauge can be jury rigged to the outlet and the compressor hand turned rapidly as possible to learn if you can get over 100 psi, will leak back, but should be a slow leak back. In like manner a low pressure gauge can be jury rigged to the inlet to learn if you can get a good vacuum again by hand turning.

The idler pulley should turn free with minimum side play, that bearing can be a culprit, I like to pop off a seal and see with my eyes what the grease looks like, if any. Age causes the grease to dry up and get rock hard. Check the gap between the pulley and clutch for 20-30 mils for most compressor, look at the surfaces and hit the coil with 12 Volts for a sharp click and pull in. Prefer monitoring the input current to see if it does indeed decrease as the coil heats up. A coil with shorted turns does exactly the opposite, coils short out when heated up and the current will go up, that's a problem.

If all good, flush the compressor out with the oil you intend to use, make sure it's drained then install it, also good to check the O-rings if a HPCO or relief valve is used plus a new gasket or O ring to installed it.

Yet another very important bench test is to plug off the outlet, jury rig in a 100 psi air pressure and submerge the compressor in water not much different than checking out leaks in a car tire looking for air bubbles. If it passes all these tests, should be fairly safe to put in the vehicle, but a lot depends upon your feel of hand rotating, all may look good, but with worn bearings or piston slap and full load may be noisy in actual operation.

Kits are available for the jury rigging, but can make your own by getting the fitting off a wrecked vehicle and welding the ends shut especially for the leak tests.

Is this worth the effort? Only you can be the judge of that, is time consuming and can be disappointing, can see why a professional wouldn't fool with this and install a new or a quality rebuilt with a warranty, unless you are happy to work for about a buck per hour.

lv6l on Sat August 02, 2008 7:42 PM User is offline

Ok, I went and took another reading today and this is what I got. Ambient temperature is 80F Engine bay temperature was about 82F

When engine is off, low side is 95 and high side is 90.
When engine is first turn on with idle at 1500 rpm. low side was 9 and high side was 120.
When engine is on with throttle being held low side was 5 and high side was 115
When engine is warm up a bit with the throttle held to see how high I can get it up, low side did not get any higher than 0, and high side go at highest of 120.

So obviously I have a leak now. Before a few days ago when I made this thread my AC was working fine, it just started getting warm, but now it will not even blow cold. It was working perfect for a about 2 months when I charged it. It always took a bit longer than normal cars to get down to peak cold temp. but I thought that should be normal considering when I took my reading back then it seem like I had a weak compressor. It would take about 10 min. of constant driving to get the vent temp down to about 40F. But now vent temp will not go any lower than 78F

I guess my next stop is to re-vacuum it and let it sit and see if it leaks. How long should I keep it for? last time I read on here you should keep it for about 10-15 min. Maybe this time I should keep it longer? What do you guys think? Thanks.

NickD on Sat August 02, 2008 9:22 PM User is offline

You are losing refrigerant and best to find that with charge left in the system, applying soap and looking for bubbles is one way with more major leaks, or getting an electronic leak detector. Vacuum is not a good way to find a leak as air is leaking in rather than refrigerant leaking out, and refrigerant can be detected where air is everywhere.

lv6l on Sun August 03, 2008 4:24 AM User is offline

Can I buy one of those can of dye and put it in? Then use a UV light to find it?

NickD on Sun August 03, 2008 8:05 AM User is offline

Left that option off, but does help to clean up your engine compartment first, this site does offer a UV black light. One common area for leaks in your vehicle is that coupler into the expansion valve, does it look corroded? But with a vehicle that old, a leak can be anywhere. Guessing you have a very small leak, not exactly like refrigerant is pouring out faster than you can put it in. So will take some searching.

lv6l on Sun August 03, 2008 7:35 PM User is offline

If I add in the freon with the UV dye, and when I go and search for it, will older dye from previous user show up as well?

lv6l on Tue August 05, 2008 5:01 AM User is offline

Bump

lv6l on Thu August 07, 2008 1:03 AM User is offline

bump

If I add in the freon with the UV dye, and when I go and search for it, will older dye from previous user show up as well?

HECAT on Thu August 07, 2008 8:26 AM User is offline

Maybe you could rephrase the question; very difficult to answer the "Will I see it, if I look?" question without sounding like a smart a**.

Will dye previously installed still be there? Yes, if you have not removed it; where would it go?


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FLUSHING TECHNICAL PAPER vs2.pdf 

NickD on Thu August 07, 2008 9:30 AM User is offline

Dyes are only effective in locations where the dye can be forced out of a leak with the refrigerant forcing it out. In a clean system, can also see traces of the oil being forced out as well. Finding a leak is tantamount to finding a needle in a haystack.

Then we are dealing with a vehicle already 14 years old with how many miles on it? And what's to say if one leak started, you repair it and another leak will start a week down the road. I like to evaluate the entire vehicle before making decisions before spending my cash. The cheap method but time consuming one is to examine each component of the system, if just joint leaks, clean and repair them all, if corrosion is found on the evaporator, condenser, compressor, receiver, TXV etc., how severe is that corrosion and in my opinion, will these last. How stiff are the hoses, any cracks?

If you are planning on keeping this vehicle for awhile, may be worth looking at an ACKit, can be far cheaper in the long run.

lv6l on Thu August 07, 2008 4:19 PM User is offline

Quote
Originally posted by: HECAT
Maybe you could rephrase the question; very difficult to answer the "Will I see it, if I look?" question without sounding like a smart a**.



Will dye previously installed still be there? Yes, if you have not removed it; where would it go?

Well, I am new to the automotive AC world and anyone like me would not know if dye would disappear over time or would be stain forever. The common sense choice would be yes it would be there forever but it's ignorant for me to assume that. That's why I ask you guys for a better knowledge of things.

Now, last question, if I decide to use those freon bottles that claims they patch up small leaks, would it work?



Edited: Thu August 07, 2008 at 4:19 PM by lv6l

HECAT on Thu August 07, 2008 4:37 PM User is offline

In regards to your previous question. There are no stupid questions.

I am glad you asked about sealers before you used. No No No

Nothing needs to be in the system but the refrigerant and oil it was designed for. These sealer products are designed to pray on the uneducated consumer by playing on all their desires and wants (a simple and cheap fix). What they can do is set up hard inside the system and cause the need for total system replacement to ever get A/C back.

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HECAT: www.hecatinc.com You support the Forum when you consider www.ackits.com for your a/c parts.

FLUSHING TECHNICAL PAPER vs2.pdf 

Chick on Thu August 07, 2008 4:48 PM User is offlineView users profile

Quote
Originally posted by: lv6l
Quote

Originally posted by: HECAT

Maybe you could rephrase the question; very difficult to answer the "Will I see it, if I look?" question without sounding like a smart a**.







Will dye previously installed still be there? Yes, if you have not removed it; where would it go?


Ah, you made the question more clear..You mean if it already leaked out..Ok, sometimes, depending on the dye, it will degrade and disappear, other times it will still be there until it's "washed" away. If you see dye, old or new, try to determine if that is a leak source.. usually you can tell a fresh leak from an old one though.. And as Hecat said, "NO to sealers", we call them death kits, and they make a lot of money for us during the summer, that is, repairing cars that used them.. hope this helps..



Well, I am new to the automotive AC world and anyone like me would not know if dye would disappear over time or would be stain forever. The common sense choice would be yes it would be there forever but it's ignorant for me to assume that. That's why I ask you guys for a better knowledge of things.



Now, last question, if I decide to use those freon bottles that claims they patch up small leaks, would it work?



-------------------------
Chick
Email: Chick

---------------------------------------------

Freedoms just another word for nothing left to lose

mk378 on Thu August 07, 2008 6:01 PM User is offline

Dye usually only comes out of leaks while the system is running. After putting the dye in you need to have a full charge and drive often with the A/C on. It stays around for a while but can get covered over by dirt. Wherever there is dye there will be oil, which shortly afterward attracts the dirt. Engine cleaner in a can will remove dye, dirt, and oil. Also if you use a 12 oz can of R-134a with dye, be sure to hold it upside down while charging or the dye will just be left behind in the bottom of the can.

Edited: Thu August 07, 2008 at 6:03 PM by mk378

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