Using OBD2 port adapter to check air conditioning

When not running (static), the pressure equalizes throughout the entire system. This is true even if different parts of the system are at different temperatures. There is always a mixture of liquid and gaseous refrigerant (unless it is completely empty). The liquid refrigerant will collect wherever the coolest temperatures are. If the inside / outside temperatures are equal, then the chart gives you the expected saturation pressure. If the inside and outside temperatures are different, then you would use the lowest temperature to lookup the static pressure (because that is where the liquid Freon will be located). There will be times when the inside is cooler than the outside, and vice-versa depending on the scenario leading up to the measurement.

Bottom line - If the temperatures are both the same, the expected result is obvious. If they are different, then I will use the lower of the two when looking up the static pressure.

 

That is very interesting. Using the lower Temperature as the variable, as you indicated, we can add this one more data point for me.

Inside/Outside Temp: 82.4F/78.8F
A/C Pressure: 90.5 psi

 

@vicw: Your original measurement (that seemed low) is suspicious. Your other static measurements fit the curve well:
Then again, I am no expert (even though I am good at faking it)... I could be off-base with an assumption somewhere along the way. More data from more people may help to guide our understanding.

 

@MrFixit: Yes, I agree. More data from others, and myself, will help to show the true patterns and consistency of the data. For this latest point, it seems that having used the higher temp would have put the result in a more direct line than what we have now, but I am sure you are correct with the lower temp as the correct one to use. I can't believe the low temps were are having in the Southeast currently - it's 50F. right now. That's messing up our data collection at the moment. I expect we will be seeing higher temps soon, though.

I'll make it a point to continue to take readings frequently to see how repeatable the data are, at any given temperature. for the static and operating pressures.

Lest there be an concern about the "questionable" data points on May 4th., here are screenshots of both readings.

 

I'm not sure whether this will add but here goes...

Static A/C Pressure (pulling out from garage in the morning)
Temp OUT: 59 F
Temp IN: 71 F
A/C Pressure: 67 psi

Operating A/C Pressure (afternoon on a sunny day, AC running)
Temperature OUT: 73 F
Temperature IN: 84 F
A/C Pressure: 110 psi



Anyone have the AC smell? Once it starts stinking, it won't go away for a very long time. I did the KlimaKill sanitizing through the drain tube and the smell was still there for a few more days. Now it's all gone and I try not to run the fan without the AC if I used AC that day. On other cars I always try to turn off AC and let the fan run for at least 5 minutes thinking it'll dry out the moisture, but maybe that's not good for this car.
I was thinking of drilling a hole on the plastic housing so I can squirt Lysol as needed if that makes it easier to sanitize the evaporator. Not sure where things are so.

 

I wasn't so much doubting that you recorded the data properly, but rather, some assumption about this whole thing being wrong. We don't really know where these temp sensors are located, and are assuming that they represent the temperature of the Freon in some way. We also don't know where the pressure sensor is (important when understanding the operating case).

@Hoon: Your data shown below... Seems to be 'reasonable'.

 

No problem... I've been doubting my recording of that questionable reading from May 4th myself, and have rechecked it may times. I included the screenshot just as a reference to how it was derived. It seems to be an aberration from the norm, based on my subsequent data points, which is good news to me, since it lessens my concern about a possible slow leak in the system. Going back through the May 4 sequence of events, I did notice that I had the Climate Control ON, briefly, about 40 minutes prior to the Static Pressure data capture, and perhaps the system was actually in transition, resulting in an aberrant reading.

I also captured one more Static Pressure reading this cold morning.

Temp OUT: 64.4 F.
Temp IN: 62.6 F.
A/C Pressure: 68.02 psi

I'm also wondering how the chart will handle clusters of data in close proximity. It will be good to see them bunched up, giving more credibility to the data collected, but it may become impossible to decipher individual inputs.

 

So more questions: Using the famous Autel scan tool, I have the following data on an approximately 15 deg C day (59 deg F for those not yet on the metric system ) The pressure increases when I switch the AC on and falls when I switch it off, although I can't hear the compressor. (Maybe that's as it should be)

AC On: 480kPa (=69.6 psig)
AC Off: 391 kPa (=56.7 psig)

However using my hand as a temperature sensor, I can't detect any temperature change in the car.
The pressure seems to correspond to the chart from Mr Fixit (thank you)
Shouldn't I be getting some cooling with that much pressure in the system?

Thanks

 

Well, I'm not sure...
It was only 59 degrees out, so you don't really even want any cooling. Did you have the indoor setting less than 59 degrees? It won't cool if it is already cooler than the setpoint. What was the inside temperature reading?

Maybe some of these readings will make more sense as it gets warmer outside and A/C is really needed...

Here is the plot with your new data... It is getting cluttered and hard to read the labels. Trying to work on an alternative format.

 

Set at 75 degrees after 25 minute drive:

Temp out: 91
A/C Pressure: 137
Temp in: 84

 

Thanks to @Danks for providing some guidance, we now have a shared spreadsheet to capture Clarity AC Measurements.
I have populated it with all the measurements to date. It may evolve for a while.

You can enter your own measurements, or I will to continue to populate it if you post your results here.

The spreadsheet has two tabs:
The first is "AC Data" - This is where you enter your measurement.
The second is "AC Chart" - This is where you can view the result.

Hopefully it is clear as to how to enter data. The Outside Temperature is 'required'. You enter your pressure in the appropriate column (either static, or operating). New data will appear on the Chart tab automatically.

All the measurement points are labeled with the user's 'name', but this is getting cluttered on the chart. We can turn the labels off, but then it is harder to find your individual data. One option is to abbreviate the labels, but I am open to suggestions as to how to improve this.

Here is a link to this shared spreadsheet:
https://docs.google.com/spreadsheets/d/1tXv2EokPhpR-TtucHWp6pGo8m97MPip9s97kPDQMqw4/edit?usp=sharing

For reference, here is what the current chart looks like:

 

Great job @MrFixit and @Danks. Love the shared spreadsheet, and individual entry approach to data entry and chart display, with the added advantage that it is always to be found in the same place.

I think a cluttered name display is pretty much to be expected, assuming there is a significant participation, and having them clustered tightly is a good thing, since it can show consistency in our results.

I'm wondering if there is a line showing the expected operating pressure results, in the same fashion as the current one for static pressure. If not, I guess our charting will build one, that will at least apply to the Clarity, as more data is reported.

 

@MrFixit has the spreadsheet set up so that we can enter our names, but also a label for our data that is shorter than our name. I suggest that we try to use labels that are lower case and at most 4 characters long. That will reduce the label footprint on the chart and help some.

 

Is it possible to get the label to appear in the small pop-up box that appears when you put the cursor over the data point? That would make it easy to check to confirm your individual posts.

 

Yes, it is possible. If very many people participate, I expect that even the data points will crowd together. Ideally, all of our data will be crowded on, or very near, the saturation line at every temperature we check.

 

Just checked my static AC with Car Scanner. I noticed that it took a little while to settle in on a number. It was bouncing between 72. something and 73.39. It finally settled on 73.39.

FWIW - I took the dashboards MrFixit made and made my own.

 

Sounds good.
When you saw the bad condenser, did it look more like a factory defect or a rock strike?

 

I have been wanting to check my AC pressure as well before my warranty ran out but had not done so yet. However, when driving last night, the air temperature coming out of the vents was only slightly colder than the outside air (and it was in the mid 80s). I normally put climate on auto so I turned it down to high 60's but no difference. Even switching directly to AC on didn't make a difference. I was sure I had the same failure as others. When I got home, I tried to measure my results. However, I do not have the Vgate scanner, just a cheap OBD2 ELM scanner and an Autel AP200 (Vgate is now ordered). I wasn't able to find the AC pressure in the Autel Scanner, but loading the Clarity profile in Car Scanner did pull up the AC Pressure.
Here was the measurement I took after the car had been parked in shade for a couple hours with windows down:
AC Pressure 90.5 (ranged from 89.5 to 91 but eventually settled at 90.5)
Outside Air Temperature (from instrument panel as it didn't load with my cheap scanner) 81
If the readings can be trusted (since I didn't have the Vgate), then either I have an entirely different issue with the AC or I really don't have an issue with the AC (however, my wife also confirmed the AC didn't feel cool either)