If you want to DIY, get yourself a real set of HVAC gauges.


You do not want the air temp to get below 32F or 0C because ice will form on the evaporator which will prevent the cabin air from flowing through the evaporator. If the air doesn't flow through the evaporator, it can not give up its latent heat, so no cooling effect will be felt at the vent. If you look at the image of the gauge that I posted you will see a temperature in Celsius or Fahrenheit. Follow the needle to the psi reading and that is what your psi reading can produce in the way of temperature at the coil. So a low side psi reading of 35-40 should be where you want to be.

 

I am getting a low side 35-40 reading when the car is idling. However, when I push the gas to 3k rpm it dips below 25. This must be the issue. So I just put in refrigerant until I can get over 30 while it is running at 3k RPM right?

 

I put like half a can of refrigerant in there to where it was reading about 45 to 50 psi while idle and when I gave it gas it dipped down to 30 however now the clutch disengages and the cold air immediately stops blowing out. Of course as soon as that happens you see the psi at 100 in the red. Maybe I need to release some? How do I do that?

 

I figured it out, never mind. Whew, I got scared there for a second. Excuse my nervousness but I don't know shit about cars. When I saw that the clutch was getting kicked off I got scared I messed my AC up worse than what it is. So I let some 134 out and it stays on now and I am getting 45 psi while idle and like 25 at 3k RPM. I honestly did not let that much out. Another thing to note is the recycle air setting and fresh air setting. All the previous reading I have been was with the recycle set. I also notice twice now that when the AC stops blowing cold air switch over to the fresh air setting the AC begins to blow cold air again. It happened once today and I thought it was a coincidence but then it did again while I was fiddling with it tonight.

 

You have the idea. If it still freezes now I would raise the pressure about 3 PSI from 25 to 28. All you are trying to do is to tweak the pressure (charge) a few PSI to keep it from freezing. It does not take much. If you add too much you will trigger a sensor on the high pressure side the will cause the clutch to cycle. Some cycling is normal. The rate and duration of cycling changes base on a lot of dynamically changing things. They are primarily temperatures and rate of heat exchange (air flow) across the condenser and the evaporator.

I am trying not to give you too much technical BS here. I am doing my best to keep this as simple as possible. I figure you are just wanting to fix your car on a one time basis and not to become an HVAC technician.

 

LOL Its fine, I don't mind the extra info. You can never know too much. However, I am quite at a loss as to why 4 different mechanics, one a confessed 20-year AC expert and one at the Honda dealership (a big one I might add) could not diagnose this problem. From the way you talk about it, it seems like a fairly common issue. I explained this to a co-worker and he said that happened to his home AC unit (frozen condenser). Everyone one of them said, "Unless it ain't working when you bring it in, we can't diagnose." Which of course was impossible because even if I waited until it went out and brought it straight to them, by the time they looked at it (while I sat waiting for my turn) it was working again.

So I guess I need to make sure that I can get the psi to be above 25 while 3k rpm then? I saw the chart you gave the link to and saw how it freezes if its below 25.

 

Here is the problem with the automotive A/C maintenance / repair business today. They tried to make it simple for the technician and now today most only know how to run the automated machine and read the results. You install the AC machine and let it do it's thing while you go drink coffee or work on something else. This works well for 90 to 95 % of the time and is a good money maker requiring less people skills. If the machine says it is OK you are done. The problem is what to do when the machine says OK and the customer still has a problem. We have the same problem with computerized cars. The PCM and BCM codes are very efficient at quickly diagnosing most problems for the tech and the tech becomes a parts swapper. What happens when swapping does not fix it or when you have no codes to read?

A residential AC tech knows a more on how the systems work and does more diagnosis, but when you put him in an automotive environment he sometime gets lost because we have many more variables to work with such as temperatures, air flow, engine speeds, etc. So when working on things the the AC machine does not find or fix, you need a tech that can use a basic set of AC gauges, and a thermometer to find the problem or fine tune the problem.

To give you an example. When I got my 2005 Chevy Colorado it would start shutting down the compressor for longer and longer periods of time (cycling) as the outside temperature went above 90. Three evacuate and recharges on two different AC machines (one by the dealer under warranty) all gave me the same result. Finally one day when it was above 90 and failing, I attached a set of gauges to it and ran the hoses to the rear of the hood. I set the gauges on the window so I could see them inside while driving. I drove up and down the 1+ mile taxi way at my airport watching the gauges. l saw the problem in less than 2 miles. The high side was exceeding the high limit (a little over 400 PSI) at speeds over 35 to 40 mph. I bleed off just a very little R-134 to keep it below thehigh side upper limit and have been driving that vehicle for 12 years with no AC problems.

One thing I have noticed on Hondas. I have seen many of them new out of the factory charged slightly below ideal. Why they are that way, I do not know.

 

Hmm, so it looks like yours was overcharged to begin with huh? Its crazy that they bled and overcharged it every time. I would like to add the detail that my car first did this about 4 years ago one very hot summer day on a semi-long road trip which backs up your statement that Honda sells them undercharged.

Today after work was a good testing day because Fridays I always get stuck in traffic and it is very hot at 4:30PM so I would lose the AC just about every Friday before I got home and today I did not. In fact, it blew REALLY cold the whole way. The only thing that has me slightly skeptical that the issue is resolved is for some weird, freak reason it was not your typically really hot day today. Its usually in the mid 90s around that time and today the highest it got was like 86. But I really have my fingers crossed and either way whether it is fixed or not I am really grateful and downright impressed that you were able to outwit multiple "professionals" that I visited. Thank you once again and I will report back once I see that the issue seems to be really resolved.

 

I can not say that Honda always under charges them. It is just I have seen quite a few new ones that were that way.

On my Collie, It probably was over charged from the factory. The first recharge was done by the dealer. The second and third were done my me using a different machine. These machines extract the existing refrigerant and then recharge by weight. So out of 4 charges I believe all were over what was required. It was not by much. I have seen where two identical vehicles will take slightly different amounts. Usually it does not make enough difference to hurt anything. Occasionally you get burned.

OK on your test today. If it does fail again, you now know how to change it.

Good Luck