School me on the AC System - General Technical Questions - Tech Section

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Tsquare
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The air conditioner in my truck has always worked well enough to hang meat when it was 100 degrees outside. It will still freeze me out but is slow to get cool when I first turn on the system. It wasn't like this last year. I have a set of AC gauges and the pressure is in the upper 3/4 of the green area of the gauge.

I know just enough to get myself into trouble. As far as I know everything is original and I have never added freon in the time I have owned it. With an AC system that is 14 years old what can I do to service it? Or what is probably worn causing the slow spin up of the system?

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Posted: Wed Jul 4th, 2018 05:27 pm

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CBB9M
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I tend to take a backseat on AC service in forums, but I'll throw out a few pointers to get you headed in the right direction.....

a) Verify there are no obstructions to airflow across the condenser (bugs, etc) and evap coils (mud, etc).

b) Verify that blend door closes off airflow across heater core.

c) Look for traces of refrigerant oil at each connection in the AC system. This includes around the front of the compressor since it has a shaft seal.

d) Hook up a gauge set, ie, a gauge on the suction side and one on the discharge side, and with the AC on + fan on high, engine held at 1300-1500rpm and ideally an ambient temp of 80+ degrees, note the pressures with the system at steady state and over a brief time. You watch over time for variations because this could be useful in the diagnostics.

The numeric pressures at system steady-state are important and this "upper 3/4 of the green area of the gauge" is totally worthless as it does not specifically quantify (

Last edited on Wed Jul 4th, 2018 05:32 pm by CBB9M

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Posted: Wed Jul 4th, 2018 05:34 pm

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CBB9M
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^^^^ Forum software has TWICE not posted what I typed and proof read after the last (, and I'm not going to type it a third time only to see the same fecking result. :angry:

Last edited on Wed Jul 4th, 2018 05:35 pm by CBB9M

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Posted: Wed Jul 4th, 2018 08:24 pm

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Tsquare
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CBB9M wrote:
I tend to take a backseat on AC service in forums, but I'll throw out a few pointers to get you headed in the right direction.....

a) Verify there are no obstructions to airflow across the condenser (bugs, etc) and evap coils (mud, etc).

b) Verify that blend door closes off airflow across heater core.

c) Look for traces of refrigerant oil at each connection in the AC system. This includes around the front of the compressor since it has a shaft seal.

d) Hook up a gauge set, ie, a gauge on the suction side and one on the discharge side, and with the AC on + fan on high, engine held at 1300-1500rpm and ideally an ambient temp of 80+ degrees, note the pressures with the system at steady state and over a brief time. You watch over time for variations because this could be useful in the diagnostics.

The numeric pressures at system steady-state are important and this "upper 3/4 of the green area of the gauge" is totally worthless as it does not specifically quantify (
Flow is not an issue. Blend door works as designed. I see no trace of oil/grime at any of the AC connections. The gauge I have shows that I am about 45 psi on the high side with it being 88 degrees outside - it is a cheap gauge. Once I am up to speed and 10 minutes down the road it is blowing 41 degrees from the center console. It drops off 5-7 degrees on the outer vents.

I am thinking that the compressor might be going south but it will work fine at speed. At idle it does seem to struggle keeping up. I have a temp gauge in the center console to let me know what is going on right now.

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Posted: Wed Jul 4th, 2018 09:01 pm

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CBB9M
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45psi is illogical on the high side (because that equates to ~50 degrees F and a static system); on an 88 degree day it'll be over 200 PSI on a properly operating system. On a properly operating system, largely, the magnitude of the discharge pressure will be a function of the outside temp and air temp entering the evap, which is usually outside air temp. Higher ambient temp, higher discharge pressure, more heat is being removed from the cabin air.

*Once upon a time I serviced a struggling AC system that presented with seemingly high discharge pressures for the ambient temp. Pulled the radiator and ~1/3 of the area between the condenser and radiator was covered with trapped weeds, ground up leaves and various remains of dead bugs. 10 years of crud causing a flow restriction; if the condenser can't reject heat using all the airflow it's designed to have passing through it, then up goes pressure and on a hot day, performance can be adversely impacted.

Last edited on Wed Jul 4th, 2018 09:04 pm by CBB9M

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Posted: Wed Jul 4th, 2018 09:28 pm

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Like I said it is a cheap gauge and I am a novice to AC systems.

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Posted: Thu Jul 5th, 2018 12:04 pm

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CBB9M
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Suggestions:

* Acquire a reliable gauge set and take pressure readings under the circumstances noted earlier. Put the gauge that is off by 4X+ in garbage. It was on the high side and not the low, right?

* Verify that there is no obstruction to airflow across the condenser.

***There are other things to look at and rule out before thinking about a weak compressor. The good news now is that, it worked fine last year and this great because and as an example, it really sucks diagnosing a poorly performing unit with an unknown history and it turns out some idiot put in too much oil and that's the problem. Curve ball surprise, and reason to not assume things without verification during diagnostics.

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Posted: Thu Jul 5th, 2018 02:35 pm

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chris

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CBB9M wrote:
^^^^ Forum software has TWICE not posted what I typed and proof read after the last (, and I'm not going to type it a third time only to see the same fecking result. :angry:

Did you try the blue arrow in the toolbar to reload the last post contents?

There is a routine that saves the typed text when you hit preview or post buttons which can then be put back in the editor using that button.

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Posted: Thu Jul 5th, 2018 03:47 pm

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I was originally going to say "it isn't easy designing forum software" and would be VERY INTERESTED in the exact string that made this happen.

Perhaps Mr. Bill would be kind enough to construct a simple notepad file in .txt format and upload it with the single upload routine OR take a camera shot or screen shot of the string that is fooling the software. That way we could cure it.

Bill it's like a browser battle. Every time we think it is right either Firefox, chrome or edge changes something that makes another routine needed and that routine inevitably messes with other routines.

Would take a staff of coders to nail it the first time and we only have like .75 total between Chris and myself, neither one of us making a dime off of it.

And poor Chris doesn't even have a ranger so the info contained on this board is irrelevant to his life at all so he is just doing this for fun when it is fun.

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Posted: Thu Jul 5th, 2018 06:02 pm

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CBB9M
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JAMMAN wrote:
I was originally going to say "it isn't easy designing forum software" and would be VERY INTERESTED in the exact string that made this happen.

Perhaps Mr. Bill would be kind enough to construct a simple notepad file in .txt format and upload it with the single upload routine OR take a camera shot or screen shot of the string that is fooling the software. That way we could cure it.

Bill it's like a browser battle. Every time we think it is right either Firefox, chrome or edge changes something that makes another routine needed and that routine inevitably messes with other routines.

Would take a staff of coders to nail it the first time and we only have like .75 total between Chris and myself, neither one of us making a dime off of it.

And poor Chris doesn't even have a ranger so the info contained on this board is irrelevant to his life at all so he is just doing this for fun when it is fun.
The bummer is, the problem isn't noticed until "post" is invoked and the post is reviewed, and then it's after the fact and it can be more of a bummer if a lot of text is vaporized. What I can do and since something similar to this happened before and I mentioned it (and I wasn't treated abnormally by an arrogant foreign dick, and I'm not referring to you) and it got fixed is, seeing how the problems seem occur when a character is used I can do a screen capture prior to posting if you like, and send it to you in hope that YOU can look at it. You as the preferred contact because not only do you care about resolving problems but it's much easier to deal with a person with some people skills. Thanks.

*Edit: I really would be more than happy to work with you on any of these strange anomaly that pop up here and there, this, in the name of "building a better mouse trap". Surely I'm not the only person using FF and W7Ult, but maybe others have simply said nothing, and in some ways I can't blame them. This, in light of seeing what can happen to people who do speak up..........

Last edited on Thu Jul 5th, 2018 06:05 pm by CBB9M

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-Bill

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Posted: Thu Jul 5th, 2018 06:57 pm

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Tsquare
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CBB9M wrote:
Suggestions:

* Acquire a reliable gauge set and take pressure readings under the circumstances noted earlier. Put the gauge that is off by 4X+ in garbage. It was on the high side and not the low, right?

* Verify that there is no obstruction to airflow across the condenser.

***There are other things to look at and rule out before thinking about a weak compressor. The good news now is that, it worked fine last year and this great because and as an example, it really sucks diagnosing a poorly performing unit with an unknown history and it turns out some idiot put in too much oil and that's the problem. Curve ball surprise, and reason to not assume things without verification during diagnostics.
I have a buddy with a good set of gauges and he also has the freon recovery pump. He is a retired mechanic but he is Apalachicola fishing this week. When he gets back he is going to check it out for me.

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Tony
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