QuestionI don't know much about AC, but I bought a kit from AutoZone that came
with a little pressure gauge. I put it on the low side of my truck's AC system.
It read close to 70 and was in the red zone. I assume that is a bad thing?
The truck blows cold air, but being that our van's AC just died, I wanted to
check to see how my truck was doing. Someone told me once that a vehicle
could be blowing cold air, but be low on lubricant that is inside the system.
If unchecked, it will eventually burnup the compressor, which is what I think
happened on our 2000 Honda Odyssey.
So anyway, how do I get the pressure into the right range on my Chevy truck?
Thanks!!
AnswerRob,
As for the compressor oil. The information that you were given was right... to a point. If your system is low on oil, the same thing that would happen to your car by running it without oil, would happen to your car. It will eventually sieze. However, on maybe 1% of vehicle compressors are you able to check your oil level. Why? There is no need to. The A/C system is a sealed system... with it running as it should nothing should ever get in and nothing should ever come out. Think of it like your refrigerator... have you ever checked the oil in your refrigerator compressor? They are the same system, there is just a few added components in your vehicle. If by chance Chevy came out with a compressor you can see your refrigerant oil in, which I do not see happening, there would be a small sight glass, on the back plate of the compressor that you would be able to see oil in. The proper oil level would be between 1/3 and 2/3 of the way up the sight glass. But again, I have never seen one on a passenger vehicle. The only one I have ever seen it on is a Military HETT (very heavy equipment hauler, kind of a semi truck on steroids)
As for your high pressure. When you checked that gauge,I am willing to bet that you checked the truck while it was idling, am I correct? Automotive compressors are designed to be operated around 1500 RPM, because this is the rate it will typically be turning while the vehicle is being driven. The faster the engine turns, the lower your pressure goes. To a point. Another variable that would come into play is the temperature outside when you took the pressure. The hotter it is the higher it will be. Pressure and temperature are relative. Kind of like when your shaving cream or a paint can runs out of pressure. If you run hot water over it, that will raise the internal presure of the can, and you will get a little more out of it. But back to yor truck. If you have never had anything done to the system then it is still charged from the factory. And I am fairly certain that they charged it to exactly as it should be.
If on the other hand, it was a not so hot day when you checked the pressure, you checked it at 1500 rpm, and you have had the refrigerant recovered and recharged before, and the gauge you used was better than most I have seen at Autozone (most are not very reliable), then I would agree and say that your pressure reading was high. The most common cause for your low pressure reading too high is just an overcharge. But Again, I do not think this is the situation because if it was overcharged, it would not be cooling as well as it should. But the only way to get it back to where it is supposed to be is to recover the refrigerant, evacuate the system with a vaccuum pump, and have it charged back to the specs on the label under the hood of the car.
But in all honestly, I believe your system is running exactly as it should and would not worry about it. The A/C system can be tempermental once it starts getting worked on. My recommendation is to not mess with it until it starts going out.
Thank you for your question, and I hope I helped a bit. If I can do anything more, send me a follow-up please. Have a great day.
