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Discussion Starter · #1 ·
Hello everyone,

I happened upon this website when trying to fix an issue with our families 1996 Ford Taurus.

A few weeks ago the A/C started intermittently blowing hot air. It seemed like when you first turned the car on the A/C would be cold for 10 minutes or so and eventually would get warm.

Starting this week, it has blown nothing but warm air. I picked up an EZ Chill A/C Recharge Kit from Walmart to see if it was something as simple as low freon level.

I turned the car on, turned the A/C to Max A/C highest fan speed and let the car run for 3 minutes, then when I hooked up the pressure gauge to the low pressure port the pressure gauge read all the way past 100. (this is with an ambient temperature of 95ºF so technically it is just past the red "ideal" pressure)

According to the instructions for the recharge kit I shouldn't add any refrigerant if the pressure is this high, unless the compressor isn't kicking in.

Which leads me to my first ignorant question:
1. How do I know if the compressor is running?

The belt is spinning but there are several things which it is spinning and I have no idea which one is the compressor.

Now for my second ignorant question:
2. Could I cause any damage by adding 1 can of refrigerant? The instructions say to add 1 can if the compressor isn't going but not knowing how to check that I thought maybe I could just add 1 can anyways.

I apologize for my lack of knowledge, I have very limited experience with automobiles but any help here is much appreciated.

Thank you
 

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Anybody can fix ac systems as long as they have a few ac specific tools, and can follow directions.

That being said, you need to buy an ac manifold gauge set so you can check the refrigerant pressure on both the high and low pressure circuits. Harbor Freight usually has their's on sale (right now the price is $50), and you can get a coupon for 20% Off from the Internet, the Sunday newspaper, of from a HF magazine ad.

You will also need a refrigerant fill hose, a cantap, and possibly the use of a vacuum pump (if you open the ac system to replace a part/s).

It would be nice if you knew something about auto ac systems. Haynes publishes a nice ac systems manual that's available from most any auto parts store for $20-$25.

If you don't see yourself buying the tools, then I suggest taking the car to the shop and paying what they ask.

The little pressure gauge that came on the can of refrigerant is very inaccurate, and can only be used to read the pressure on the low side of the ac system. To get an useful idea of what's happening on your car, you need to see what the pressure is on the high side.

The ac system refrigerant pressure can only be measured accurately when the ac system is running. When the ac compressor is not running, the refrigerant level evens out between the high and low sides, and the pressure on the low side could be 100psi and be okay. You can't tell if the ac system needs refrigerant, because the refrigerant level on the low side drops and on the high side rises when the ac system is running (which is when you're supposed to measure the pressure).

My guess is that for some reason the ac clutch is not being activated, so the compressor is not running (which explains the high pressure on the low side).

This could be due to a defective pressure sensor (cycling) switch (the low pressure/cycling sensor is easily tested, and then replaced without the loss of refrigerant).

OR, a wornout ac clutch pulley bearing, allowing the clutch pulley to wobble, and that has damaged/ruined the ac clutch coil, so now the ac clutch is not working, so the ac system does not work. If this is the problem, the repair would require the remove the ac compressor so the ac clutch pulley and parts can be replaced. This requires the discharge of the ac system.
 

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In my area, my experience with AC systems tells me that pros do it inexpensively enough that its just not worth your while doing any of it yourself unless you already have the tools you need and already know what you need to know.

The cans with the gauge are dangerous to use. Allow me to explain several situations that can go very wrong and make these DIY cans a risky decision.

AC systems are charged by watching the relationship of pressure versus temperature, but that it really not quite enough, you need to watch both high side and low side pressure together.

So in your case, you low side is already too high and it shouldn't be added until you know whats going on. But let me throw so alternative situations that are very common.

Lets say the pressure is low, you add refrigerant. The pressure does not really rise much, despite what you are adding? Strange, do you keep adding? What could be happening is that the compressor is still working, but is in early failure, and the orifice tube is partially plugged, causing the high pressure to get extremely high and the low side remains low. Keep adding refrigerant, and something is gonna blow.

Lets say the refrigerant is just low. You add it and it now blows cool. Then in a day or two it is blowing warm again. You check it and its low. Its obvious its a leak. To repair a leak means opening the system, which you can't do yourself, so unless you have the right equipment, you are gonna need to take it to a pro anyway. The problem here, though minor, is that you have wasted your money on a refill kit, and still have to take it to a pro.

There are other situations. Particularly if you have lost all charge, the danger for moisture contamination is high. If water gets inside the system, and it will if there is any humidity in the air at all, then it mixes with the oil and forms and acid. If you simply refill, the system will not work correctly, and it will destroy the rest of the system. Plus the leaks is still there most likely.

Where I am, basic AC service can be as cheap as $40 plus refrigerant. The basic service at most shops almost always included some leak detector, and a free follow up check within a couple weeks to see if any leaks are found. Thats a hard deal to beat. The shop that I use these days even includes the first lb of refrigerant for free.

The DIY cans have their place, but they should only be used when you have the proper tools to diagnose and confirm that it is safe to add more. The minimum tool set in my opinion to do AC work is a manifold gauge set, an AC thermometer, a can tap and a can of refrigerant or a DIY kit. If you want to be able to detect leaks, you will need a dye injector and dye, plus a blacklight and some yellow tint goggles. You can get most of that in a kit. To open and service the system, you need even more specialized tools. You need a vacuum pump or evac machine. In my opinion, if you need to open the system, you can save money by having a pro do it and then fixing whats needed, then take it back to a pro to have it evaced and recharged again. Don't even think about opening the system unless you already know what you are doing. This is because many AC components must be replaced together and the system flushed, so if the problem is more than a faulty seal or hose, you really can't do it yourself cost effectively.

So things to watch out for in a DIY kit. If it has premixed oil, or leak stop, or synthetic boosters you should not buy it and should take it back. A proper DIY kit will use an oil/dye injector to let you add the correct type and amount of refrigerant. Stop leak products are bad for the system and will cause it to fail and are temporary at best and are no substitute for a proper repair. Synthetic boosters are a contaminant, usually a small amount of a different type of refrigerant that makes the system run colder. This is not needed on a properly working system that has the right pressures. and especially in weather that is not that hot, can cause the system to overcool. If the evaporator drops below 32F or 0C, the evaporator will ice up and freeze. R134 is designed to be able to hover slightly above this temperature, so no booster should be needed. These boosters are often added to compensate for inaccurate gauges included with such kits, and will mask the effects of an incorrect charge.
 

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Pressure too high on the low side with a DIY kit indicates your compressor is not running.
 

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Discussion Starter · #5 · (Edited)
Thank you everyone for the extensive information and help with my problem. I will look into a manifold gauge set and see if I can pick one up for <$50, then report back here after checking the low and high pressures...

Question, do I need the A/C running on maximum for 3 minutes before checking these valves or can I just check them while the car is off?

Also Khan, the a/c recharge kit I bought is this one:
http://www.walmart.com/ip/EZ-Chill-AC-Recharge-and-Retrofit-Kit/16888792#Specifications

I believe I remember reading somewhere in their instructions that it had some additives to stop leaks near the o-ring washers.

I will also see if I can call around and get a quote on what it would cost to have a shop do the work. I'm not opposed to taking it in to a professional, I just don't want to pay hundreds of dollars for something I could do myself for $50.
 

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Nope, I'd take that kit back.

AC systems require the correct lubricant for optimum longevity. When you buy kits that already have a lubricant mixed in, you have to assume its really the right stuff. The wrong lubricant may still work, but over time it can cause premature failure. Its like taking a car that is designed to take 0w20 motor oil and running 10w40 in it instead. It won't hurt it in the short term, but over time, it can cause accelerated wear.

Stop leak additives do more than plug the leaks, they also plug the orifice tube, condenser, evaperater, and can damage the compressor.

For $50 you can save yourself the cost of your own gauges and some shops will cost about that or less. Don't forget, you don't just need the gauges, you need a repair manual. I would consider that a mandatory tool. You also MUST have an appropriate type of thermometer. You need to be able to measure ambient air temp and the temp coming out of the vents.

Worst case scenario with having a pro check it out. They charge you the diagnostic fee and you decide not to fix it. If it is broken to where it would cost hundreds of dollars, it is outside the scope of just adding refrigerant anyway.
 

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Let me add my 2¢ based on my experience. Do few visual observations, verify your hoses are in good shape and look for signs of refrigerant leakage. Based on the age of your vehicle I would put in refrigerant oil before before R134. And with the Ford compressor you just can't put any oil in, it has to be what is required by Ford. I can't remember the name of it off the top of my head.

Hoses must be in good shape with no signs of oil leakage.

2nd, there is a switch I believe near the receiver-drier, if the switch senses too much pressure or too little it disengages the A/C compressor. This switch cycles the A/C compressor on and off when things are "normal" - blowing cold air.

If the pressure is in the "sweet spot" the switch makes the circuit to run the A/C compressor. When the pressure drops due the compressor moving refrigerant the switch breaks (off mode) the circuit to the A/C compressor. When the pressure builds up in the receiver-drier the switch (on mode) completes the circuit engaging the compressor again. You will hear the compressor cycle on and off with a healthy A/C system. It makes a distinct "clicking" sound of engaging and disengaging.

If your low on refrigerant there isn't enough pressure to cycle the switch, and if the switch doesn't cycle neither will your compressor. And if your compressor is low on oil you're going lock it up. Keeping your A/C running healthy is a science and art all in itself.

Monsoon
 

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Discussion Starter · #8 ·
Thank you again for the advice... I called a mechanic I've taken my car to before to see if he can just to a diagnostic and tell me how much it would cost to fix... If it's <$100 then I will pay it no problem...

I have just had bad experiences in the past with mechanics where I have paid them to fix something and I have later found out from someone else that the mechanic either overcharged for the service or "fixed" something that didn't need to be fixed.
 

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Discussion Starter · #9 ·
Just thought I would update everyone on the car. I took it to a mechanic and he said the freon levels were just fine. He drove it around for a bit and he said the A/C started working during the drive then stopped after a while again.

He told me there is some door or switch that allows cold/hot air through and the little switch was broken so that cold air wasn't getting through. It only cost $60 to get the part replaced and the A/C is working great.

Thanks for the help/advice everyone.
 
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