Hello all,

I have a 2011 Fit, base model and I am having an issue with the AC where it blows perfectly cold air but after constant engine running on a highway for a half hour or so it stops blowing cold air. If I turn it off fo say another half hour, it begins to blow cold air again. I have taken it to 3 different shops and it seems if you let the car simply idle, it never goes out. They told me they let it run for hours and it never went off. The funny part is it seems that it is in the afternoon during the hottest part of the day that this happens. In the morning where it is not as hot but I am running the AC just as hard it never goes out. Always, always, always in the afternoon. I've had them change the relay and still nothing. No one can figure out what it is. If anybody has an idea that I can take to the shop I would be forever indebted. No AC in FL during the summer really SUCKS. LOL

Thanks in advanced.

 

I had this issue as well on my roadtrip from CA to WA last year.... The AC decided to stop blowing cold air when the outside temp was in the mid 90's....

 

Did it come back? The first time it happened to me it was YEARS ago and of course, I took it to a shop and since it was working they didn't know what to look for. It didn't happen again to until a couple of years later but nowadays it seems to happen every few days. Very frustrating as it begins to work again by the time I get to the shop.

 

I have a feeling it just needs a freon recharge. I haven't done mine yet as it seems to blow fine when it's not that warm out....

 

I have probably posted this 5 times over the years. You have the symptoms of a slightly low refrigerant charge. What happens is as the charge level goes down the evaporation point of the refrigerant also goes colder. At the point when it gets to 32 F or lower in the evaporator, the outside air moisture that accumulates on the evaporator freezes instead just condensing of draining off. If you turn the car off or keep running the car with the AC off, the ice will melt and when you turn the AC on again you will have cold air again.

That said the question is what to do. Go to Walmart in the housewares section. Get yourself a $10.00 digital meat cooking thermometer. Stick it in the center vent of your car and start driving with the AC on. If during your travels the temperature in the center vent ever goes below 40 to 42 F, you do not have enough R-134 in the system.

If you want to fix it yourself, go to Walmart in the auto section (except in Wisconsin) and buy 1 can of R-134 and a charging hose with gauge. Install 1/4 to 1/2 can of r-134 and drive the vehicle. Now watch the vent temp gauge and see what the minimum temp is that you ever read. If that minimum temp has risen to 40 to 44 F you are fine. DO NOT PUT MORE R-134 IN THE SYSTEM THAN IT NEEDS. if you do, the temperature will rise even higher and you will be unhappy as it will no cool as well as you want. If you haven't reached 40-40 obviously add more refrigerant as required.

Or you can take it to someone and put it on an AC machine. AC machines do not charge refrigerant by temperature or pressure, they charge by refrigerant weight. This usually works and almost any dummy can run the machine without needing to understand how things work.

When it does not work for several reasons, you need to get out a vent thermometer and gauge and tweak it as above for best performance.

BTW, almost anyone who does home / commercial AC systems does them by temperature and pressure. They would understand how to set the refrigerant charge correctly in you car without a machine.

Good Luck.

 

Thank you so much for the thorough instructions. I will give it a go. So what you are saying that if the AC goes below 40 to 42 that means it doesn't have enough coolant but adding coolant will raise the temperature? Sounds backward since what you are stating the goal is to raise the temperature. Shouldn't the colder it blows the less coolant it needs?

 

At first look one would think that as you add refrigerant the system would run colder. That is not true. What you are playing with is the evaporation temperature / pressure point of the system. As you add refrigerant you also increase the pressure at which the refrigerant evaporates and the temperature in the evaporator. What you are trying to do it to make sure that the evaporation point is above freezing temperature of water. Your problem right now is that the water that is condensed from the fresh air and collected on the evaporator is freezing. Once frozen over the air that is suppose to blow through the evaporator can not go through it and be cooled due to the accumulated ice.

Clear as mud right? I do not think I explained it clearly. If I haven't, let me know and I'll see if I can find a better explanation somewhere on the internet. Maybe on Wikipedia.

 

Actually, that was a pretty good explanation. I will definitely give it a shot. I appreciate your help.

 

So I finally got the temp gauge although I haven't picked up the 134a and I stuck the gauge in the AC vent and let it run full blast for about 20 minutes and the coldest it would get to was 53 degrees. So would you say that it most definitely needs a coolant boost? I am a little scared to boost it myself because I heard you can mess up your AC if you put too much in it but that doesn't mean I won't try it. But you were quoting 40 - 44 degrees and I can't even get close to that.

 

I recharge my 2009 fit about 3 weeks ago with 134a from Walmart. Took temp reading and it is blowing 39 - 42 degrees F. I watched several youtube videos to learn how to do it. AC is blowing cold air now. I'm ready for the summer.

 

Good to know. This makes n9cv theory all the more plausible. I appreciate the feedback.

 

Here is what I'm saying worded differently I hope.

The 40 to 44 F point measured at the center air vent is a never go below number under any condition to prevent freeze ups. The low limit is directly governed by the amount of refrigerant in the system. This does not mean that your can always reach it. The current operating number can be much higher depending on current operating conditions such as engine speed, airflow across the condenser, intake air temperature, and intake flow rate (fan speed).

This is why I tell people to stick the thermometer in the center vent, drive under varying conditions and air temperatures. If the center vent air temp ever goes below 39 or 40, you are low on refrigerant (R-134). Expect your low temp cutoff on a properly charged system to be 40 to 44.


The capacity to cool air is a different thing. Most auto AC unit will reduce the air temperature by 35 to 40 degrees under "peak operating conditions". So if the air to be cooled is entering the AC system is at at 100 degrees then the air leaving through the front vents should be at 60-65 under the best operating conditions. You can get the temperature a little lower by doing a couple of things.
1. use recirculate if the air inside the cabin is lower than the outside air.
2. run the fan speed lower to reduce the amount of air being cooled.

Measuring temp drop is little difficult as you need to know the incoming air temp. On most modern vehicles you have an outside air temperature gauge wired to a probe in front of the grill or in the incoming air intake usually in front of the front window that will work well. If you do not have one then watch for the business/ bank clocks as you drive down the road. Take an average of them as their accuracy can be off as much as 5 degrees and 2 or 3 is very common.

Another academic exercise is to drive down the highway at a near constant speeds and watch the vent temperature change as you switch between outside and recirculate. Give the system a minute or 2 to settle down after time you switch before you take the reading.

 

So I went and picked up the refrigerant today and it came with this little air pressure gauge that shows you how much you should fill it with. I attached it to the L gauge and lo and behold it read as being full. Not only full but dangerously full according to the gauge which I think just means if you attempt to put any more in you risk causing damage to your system so I left it alone. This has to be the most frustrating issue I have ever faced with a car before. I can never recall bringing a car in for repair where no one has a clue as to what it can be. All the shops I take it to says, "It needs to not be working or we can't diagnose" and the dilemma here is while the car sits idle waiting for the shop to look at it, it will begin working again. I think my best bet is to just leave the damn thing running until they pull it into the garage.

 

After you attach the gauge to the low side, the car needs to be running with the AC on FULL COLD and the fan on MAX. The pressure should be read only when the A/C clutch is engaged and the low side pressure at it's lowest Normally the AC clutch will cycle off and on some while you are reading it.

If the clutch is not engaged, and has not been engaged for a few minutes, you will read the static pressure of the system which will be very high and in the red area on the gauge. An expected static pressure example is about 78 PSI at 75 degrees. The static pressure will be higher if the temperature is higher. I suspect that you were reading static pressure.

If you do end up adding R-134, do it with the can up so that gas, not liquid, enters the system from the can. It will take a while and the can will get cold as the gas leaves the can.

What is the pressure measured with the clutch engaged?

 

'Scuse my ignorance but I take it the clutch is engaged when you click on the AC button and you hear a noticeable noise come on and go off when you turn the AC button off, correct? The gauge reads the same whether I turn that on or off and that is around 175 with 200 being the maximum on the gauge. I did have the AC running on full blast and the AC button on and I am doing this when it is currently blowing hot air. Maybe I should check it when it is blowing cold air? I have to take the car to the shop next week for an oil change and a tire rotation so hopefully, I can get it to go out beforehand so they can see it. But I have noticed something now that I thought was a mere coincidence before. It only goes out when the AC has to work really hard to cool the car down so when it is especially hot out or the car has been left in the sun or in the early afternoon here in Florida when it is baking. It never goes out in the morning on the way to work or at night. I love the car and it currently has 100k miles on it and I plan on keeping it for another 100k if it will make it but this AC issue has actually got me considering getting a new car. Well, not really but it certainly got the wheels turning in my head.

 

Yes, you will hear the clutch click as it engages and disengages. The clutch is located on the side of the engine and is driven by the serpentine belt. You should be able to see it and hear it cycling while you are under the hood with the gauge attached. Yes most definitely you need to check it when it is blowing cold air.

The numbers you are giving me are way anything I would expect for low side static or operating pressures. I am wondering if that gauge is marked in something other than PSI.

Here is a short video of an Auto Zone of a guy working on an AC system on A GM truck. The concepts are the same for your Fit. It is more info than you need but it might help answer some of your questions.

 

So check it. Here is what the gauge reads with the AC blowing cold with the clutch not running:




And here it with the AC full blast and clutch engaged:



Now when the AC stopped working and I put the gauge on there with the AC full blast and clutch engaged it was actually showing WAY in the red between the 150 and 200 mark. Do you think this is a clue that the mechanic can use? It seems when it goes out something is not letting the pressure out.

 

OK, the pictures you posted shows me says that the charge is in the acceptable range but... I assume these readings were taken at with the engine at idle. When you bring up the engine speed you probably have lower readings with the clutch engaged. If bringing up the engine speed drops the clutch engaged pressure much I would bring up the charge / pressure some. If bringing up the engine speed causes the pressure to drop to around 20 or so and then the clutch drops out, then you definite are low.

At this point I think I would note the readings that you currently have and the outside temperature. Then I would add some R-134. I would add enough to bring up the clutch engaged pressure 5 to 10 PSI. You can always add more or go back to the starting charge reading if necessary.

This is difficult to remotely diagnose because both outside temperature and engine speed affect your readings.

What are your current clutch engaged readings when you bring up the engine speed to 2000 or 2500 RPM?

We are looking for an evaporator freeze up problem so at this point I need to ask if you have ever monitored your vent temperature as you drive down the highway? .

I have no idea what is causing your readings near 200. This high reading makes me think that you might have the gauge connected to the wrong port. That should not happen because the high side port is a different diameter.

 

OK, the pictures you posted shows me says that the charge is in the acceptable range but... I assume these readings were taken at with the engine at idle. When you bring up the engine speed you probably have lower readings with the clutch engaged. If bringing up the engine speed drops the clutch engaged pressure much I would bring up the charge / pressure some. If bringing up the engine speed causes the pressure to drop to around 20 or so and then the clutch drops out, then you definite are low.

Yes, this was all done while idle. I didn't think to rev up the engine to see if it would drop.

At this point I think I would note the readings that you currently have and the outside temperature. Then I would add some R-134. I would add enough to bring up the clutch engaged pressure 5 to 10 PSI. You can always add more or go back to the starting charge reading if necessary.

OK, if after reving engine the pressure drops a little then go ahead and add 5 to 10 or are you saying to go ahead and add that even if there is no significant drop? The outside temperature is at least 90 degrees. I have seen the thermometer that I have been using go up to 90 degrees as in that is the temperature of the air blowing out of the AC when it stops working.

We are looking for an evaporator freeze up problem so at this point I need to ask if you have ever monitored your vent temperature as you drive down the highway?

Yes absolutely. In second or third gear going under 30 mph it blows pretty cold and the temp goes as low as 40 degrees and fluctuates between that and 50 degrees. 5th gear on the highway it floats between 45 and 55 degrees and this is with the AC blowing on the second level. I noticed that if I blast the AC all the way while driving it goes up to 65 degrees and refuses to dip below that and this doesn't matter whther I am driving city or highway. Full blast AC does NOT produce as cold as air as if I left it on the first or second level.

I have no idea what is causing your readings near 200. This high reading makes me think that you might have the gauge connected to the wrong port. That should not happen because the high side port is a different diameter.

LOL I promise you it is indeed in the correct port. For one, you cannot connect to the high port with the gauge that comes with the refrigerant. The coupling does not match. I would like to emphasize that I was getting this crazy high reading when the AC was blowing hot air! Which leads me to believe that there is something going on when it is acting up that is preventing the refrigerant from flowing thus the ridiculously high reading. It was extremely difficult to even get the gauge coupled because the pressure was so high it kept pushing it off!

So correct me if I am wrong but because of your insinuations I am leaning towards it does indeed need refrigerant because of how high the temp is when I have it blasting while driving the car. Should the AC still blow 40 degrees at full blast while driving down the road?

Thank you so much for your feedback. I am learning a lot.

 

Here is where I was going with the vent temperature question. We are pursuing the possibility that your evaporator is, under some conditions, running too cold. When this happens the moisture accumulated from the outside air running through it freezes and the evaporator turns into a chunk of ice. Once that happens only minimal air can go through the evaporator and cool . Turn the car off and let it warm up for 20-30 minutes and the ice will melt and you will have cool air flow again. So if the ice accumulates at 60 mph and fan speed 2 or 90 mph and fan speed 4, we do not care. What we want is for the evaporator to never reach freezing under any condition. 40 degrees measured at the center vent at any vehicle or fan speed is right on the boundary of what is acceptable. I run mine at 40 degrees and occasionally freeze it on long trips. When that happens I push the AC button to shutoff the compressor, I continue on my way and 4 or 5 minute later turn it on again. I leave the fan running all the time and the ice melts and goes away. On my wife's car which is identical to mine only a year newer, I run hers so she never sees below 42F. It never freezes up. The minimum evaporation point is directly controlled by the low side pressure when the R-134 is expanded. So so if you bring the pressure up slightly by adding refrigerant, you will raise the minimum evaporation point a few degrees. We just want is above 32 at the evaporator or around 40- 42 at the center vent under all driving conditions.

Here is a R134a chart on the Internet:
Please look at the pressure chart at the bottom of this page. I tried to post part of it it directly but it did not take.

http://www.csgnetwork.com/r134apresstempconv.html

Notice in the first 2 columns that if the pressure under any driving condition falls below 28 PSI then the evaporation temperature will be below 32.

I would add 5 PSI to the system and see what happens. You can always bleed it off again if you do not like the results.

In response to your question "should the AC always blow at 40 degree while going down the road?

The simple answer is NO

A lot of things determine actual temperature at the vents. A few of them are:
Intake air temperature
Air flow across the evaporator (less air like fan speed 2 but lower temp of the air].
Engine / compressor speed
Air flow across the Condenser mounted in front of the engine.

I guess measurement of cooling efficiency is air temperature drop at the vents. If the outside temp is say 100F and the vent temp at maximum operation efficiency might be 60 to 55. Drop the input air temp to 80 and you might see 40 to 45. Reducing the fan speed can also have a similar effect because you are cooling less air.

A 40 degree drop at full fan speed is considered a good operating system.