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What's a normal amount of restriction for condenser?

Leggie on Wed July 18, 2012 5:58 PM User is offline

When I introduce pressurized N2 at high port by the compressor and allow to escape at the removed receiver right before it goes to TXV, I can hear it hissing for about a second or two after I shut off the nitrogen. Is this a normal flow amount of restriction through the serpentine condenser or does it indicate a blockage?

I've read that a variable compressor would barely show any difference in suction pressure with a totally closed up expansion valve, because it would try to keep suction around 20 psi by destroking.

Blocked condenser would do the same thing as a blocked TXV...

I'm only getting high side to go up to 75... and I'm not sure if its because the compressor is bad (or valve..but this one isn't user serviceable) or that I'm only getting 75, because the condenser restriction is causing reduction in flow, thus causing the compressor to destroke...

JJM on Thu July 19, 2012 12:01 AM User is offline

Not sure what you're trying to accomplish here.

Pressure bleed down, provided it's reasonably slow, is normal, but this assumes the bleed test is being done with the compressor isolated - a leaking compressor (internally or externally) will bleed down quickly.

There should be no bleed down delay with a condenser, again separately tested.

Please tell me these tests are not being done while the system is operating...


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Leggie on Thu July 19, 2012 2:54 AM User is offline

It's something I've observed while flushing out the condenser and purging out the flush solvent. Seeing at construction of tubing is like a flat noodle with multiple holes in the middle as opposed to a single tube, I wasn't sure if this is normal.

When I forward flushed it, I was able to push solvent through. I was also able to back flush the solvent out. So, I'm not sure if what I have here is normal resistance or partial blockage.

HECAT on Thu July 19, 2012 11:40 AM User is offline

The only way to truly test (restricted, partially restricted, or clear) would be by a flow/pressure drop test across the unit; this of course requires that the heat exchanger manufacturer provides such flow/drop data. This data is often readily available and part of a cleaning proof test with some high dollar military and aviation components; but near nonexistent for the automotive type component.

So this is where the hand of "experience" comes in. Is it flowing less, more, or similar to other components of similar design that you have performed this same test on? It is somewhat common and normal for some of them to seem restrictive and to "bleed off" after the test pressure is no longer applied. Unfortunately, I don't think we can answer your "is this normal?" question.

When it comes to the fairly inexpensive automotive condenser, think... Can I flush it? Do I have the tools and chemicals to flush it properly? Will I be confident in the results? It can be done, but if you cannot get there... when in doubt, throw it out.


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


bohica2xo on Thu July 19, 2012 2:12 PM User is offline

Any condensor or component can be flow tested tested. All you need is two orifices with known CV, and 3 gauges.

Just size the first orifice to give a CV greater than the test article. From that orifice, through the test article. After the test article, the second orifice. Feed gas at the operational pressure through the assembly, and check the pressure drop across the test article. Compute the CV of the test article from the data.

An MVAC compressor can make 20+ SCFM easily. For nitrogen @ 300 psig & 100f, a CV someplace between .4 & .8 would be a good condensor.

Or you could just replace it.

Here is a suggestion for the OP:

Get all of the questions about this car in to one thread. Identify the actual vehicle, and describe the failure you are trying to fix. You have several threads going on here that describe a component without any vehicle details. Like this condensor - all we know is that you think it may be bad. Not why, or what it was installed in.


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~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

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