QuestionQUESTION: i have had this vehicle for 2 years and just 2 weeks ago the ac started blowing hot air. The first step i took was the cheapest, checking the freon. i noticed that with the a.c. on max the compressor was not kicking on also i usually hear the fan kick on at regular intervals with ac on max and that was not happening either. I purchased a $20 can of freon from an auto parts store that came with a gauge. When putting this on the low side it indicated that freon was low so i added until bringing level on gauge to proper setting which in turn activated compressor. However the compressor was acting funny it would kick on and off rapidly at 1 to 2 second intervals with ac at max setting. while this is happening still ac blowing only hot air.After further inspection i noticed a blown 20a fuse for the radiator fan (Lo)so i replaced the fuse which in turn allowed the radiator fan to kick on and off at the same time that the compressor did. All of this still did nothing to fix my problem and the way the compressor kicks on and off that rapidly can't be good so if you can point me in the right direction on what next steps i can take i would greatly appreciate it. Until then I'll have the windows down.
ANSWER: Trevor,
What your compressor is doing is what we call "cycling" In 99% of the vehicles with a cycling compressor the problem reverts to a low refigerant charge. A low refrigerant charge is of course caused by a leak somewhere in the system. The right thing to do is of course have your leak found, repaired, and then charged back up. But also, I am taking into account that apparently it has been working great since 01, so your leak is probably very small, therefore it would be extremely difficult to locate. My recommendation would be to go ahead and charge it back up. If it holds this charge for a good while... say the end of next summer or longer, I wouldn't worry about it too terribly much. If it leaks out again by the end of this summer, then definitely have it found and repaired.
To explain what is happening so you can visualize it better...
Your compressor clutch engages and compresses and pushes refrigerant through the system. as the refrigerant hits your metering device a low pressure is created. These components are what creates your low side and high side of the system. Inside your low pressure line there is a pressure switch that is there to protect your compressor from extremely low pressures, as this will damage it.
Your compressor runs... your low pressure begins to drop. because of the low charge it drops too low, once it hits 17-22 psig in the low side line, the low pressure switch contacts open up shutting off the compressor. With the compressor off, pressure begins to equalize between your high and low sides, thereby closing your switch contacts and turning your compressor back on. And this continues to happen over and over again.
As for your radiator/condensor fan fuse being blown, this can be casued by several different things. I will wait to go into these until you see if it continues to blow more fuses. Otherwise I would be on here all day typing and would get absolutely nothing accomplished at work.
So, as I said, go ahead and charge it back up according to the directions on the kit you purchase. Once you do this, you should be riding nice and chilly again. I hope I was a little help in your understanding of what was happening, and finding a solution. If I can be of any more assistance in the future, do not hesitate to ask. Thank you for your question and good luck in everything.
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QUESTION: i have charged up to the standards on the can i purchased which indicates to dispense coolant until arrow is in the blue on gauge. if i add more it would be in the yellow then in the red which is yellow(alert)and red(warning) do you suggest that i purchase a better gauge which shows exact psi and if so what psi would i be looking for to know i have added enough coolant?
AnswerTrevor,
I can't stand those gauges you are talking about. They tell you absolutely nothing. Yes, I recommend you get at the bare minimum one that indicates the actual pressure on the low side. I'm not sure how much these cost from a place like autozone, but it can't be too very much. Or the other option is to get you a set of technician's manifold gauges, these range from 70-200 bucks for a decent set.
Once you have the psig gauge... make sure that the engine is running at about 1500 rpms (this is where automotive compressors are designed to normally operate) and the A/C is on. You want to charge it until you reach the correct pressure on the low side without much fluctuation at all when the engine is revved. Here is how you determine the appropriate pressure...
Take the ambient temperature (outside the vehicle) and subtract 30 from it (you subtract 30 due to it being a forced evaporator). This number you have now you need to cross reference against a pressure/temperature chart such as the one here...
http://www.csgnetwork.com/r134apresstempconv.html
This is the easiest one I have seen for non-technicians to use. Type in the number that you came up with in the degrees fahrenheit block and hit calculate. then look at the block labeled pressure and measured in psig NOT the barg. This is the pressure that you want to charge the low side to.
Example: if it is 80 degrees outside... subtract 30 gives you 50 degrees. Type that in the temp. block and calculate. That tells you that your low side reading should read a consistent 45 psig on your low side gauge. I have compared this worksheet to the chart I use on a daily basis, and it is rather accurate.
Now the exception is... if your vehicle settles out at say 35-40 psig on the gauge and doesn't change with the higher rpm, then stop. You are fully charged, it is just that your system is working more efficiently than most.
A general rule of thumb... when it is fully charged you should read a 35-45 degree temperature difference between what is blowing out of your center dash vent with the fan on high and the outside ambient temperature. So, if it is 100 degrees outside and your dash vent temperature reading is 65... it may not be as low as you would like, but the air conditioner is working perfectly as it was designed to.
I hope this helps. If I confused you at any point (I have a tendency to confuse myself when I get to typing too quickly) please let me know and I will gladly clarify. If I can do anything else, just let me know. Good luck in everything
