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I always get questions about Automotive A/C Compressor Electrical connections. What wire is ground? What wire is power? Plug changing? and so on and so on.

The first thing to know is that every manufacturer is different. Sanden ac compressor almost always has 2 wires coming out of the clutch coil. The question is always which is ground and which is power. The answer is that is doesn’t matter. Its just a loop, so you can power either one. This is true of almost all 12 volt systems. 24 volt for industrial applications will need to be looked at individually.

Many manufacturers like Visteon, Denso and Delphi use hard mounted plugs. See the picture below. This Ford AC Compressor made by Visteon has a fixed plug on it. You can see it just next to the belt. You will need to replace with the identical one. No getting around this. They do make some adapters, but you are pushing it at that point. They better have been tested to work on that application.

Most compressors come without the correct plug, this is an easy swap. Just cut the wires and swap the plug over.

What is an R4 air conditioning compressor and why is it used? Good question, but probably too much to answer here.

A rotary style compressor rotates internally at high speed to compressor the liquid refrigerant. The use of the spinning crank shaft enabled it to work fairly well and dramatically shrunk the size of compressors. It became popular in the 1980’s as a smaller, more energy efficient way to build an ac compressor.

Seen in the picture of the Chevrolet Suburban Compressor, rotary compressors were common in the mid to late 1980’s and up to the mid 1990’s. After that, the same idea of rotation was used, but in different ways. The were able to make them smaller, or use series of them to improve performance.

Today, the rotary compressor is still in use in many applications.

So one of the key steps in any AC compressor install is to turn the compressor to move the oil and refrigerant and begin the charge. The problem is that while this is common, not all compressors turn easily and many will not turn until the belt is on.

This started because someone told me they got a locked up compressor. It wouldn’t turn and wondered how that could have happened on a new air conditioning parts. Well the problem is that not all ac compressors turn by hand. Many do, but some don’t. These compressors will need the belt put on and used to turn the clutch.

This one was on a 97 Sierra GMC ac compressor. For these Delphi HD6 compressorsyou need to put the belt on, they simply are too tight. This is just the design of this style compressor. Be sure to check your book on which ones can be turned by hand and which ones cannot. The Delphi H series definately cannot. Some FS6 and others are hard to turn.

Many times when you are looking to replace a part, you have to figure out what you need first. This is true for many auto parts and in this case is true for a Chevrolet AC Compressor. In this case we needed to find a part number on the compressor to ensure we get the correct part.

Starting in about the 1970’s most auto parts began getting individual labels. This helped on the assembly line and also helps in the aftermarket. In this case when we are looking for a new ac compressor and the number will help us find an interchangeable part. It enables you to double check the part number and ensure you get the right part the first time.

These labels have lots of info on them and you can look at the picture for an example of a panasonic compressor. The key is to look for the part or model number, which in this example is noted as the compressor model. That should identify what the part is. The serial number is unique to that part and is fairly useless. The rest of the info is not that imporant, except maybe for the refrigerant type. In order to get the correct ac compressor you should be able to double check with supplier. They should be able to cross this.

I have spent alot of time talking about Black Death and showing black death pictures and i even copied them on my knol.

The black death pictures in previous blogs were of very bad systems. The picture below is from a Honda CRV Compressor. We did a quick test on the system by wiping the inside of the port. In this particular vehicle the contamination that was removed from the Sanden Compressor does not seem that much, but it is plenty to destroy a compressor. This particular compressor locked up and the system failed. Everything had to be replaced.

The lesson from this is that ANY contamination can destroy a system. In this case the level of black death may have been small, but it is way too much. It is crucial to thouroughly clean out the system to ensure you don’t destroy the new compressor. A small amount of debris will cause a compressor to fail.

I’ve spent lots of time talking about Black Death in an AC Compressor system. Even now on my knol.

Now I actually have a picture of the damage done by Black Death. You can look at the picture and see the before and after. Many people don’t believe this is possible, but here is the proof. It is pretty much proof positive that the Climate Control system is the most difficult system to work on because of its tendancy to destory other parts. Its could be classified a predator system.

I cannot stress to everyone working on this system that they must start clean. If there is any traces of contaminates in the system then the condenser and evaporator should also be changed. Do not take chances.

Let me know if you have any other cool pictures, I’ll post them up.

So someone asked if I had some PAG oil for their AC Compressor. I asked what type and how much they needed. They said they had no idea and asked if it even mattered. Wow!

I’ve talked about this before. It is very important to get the correct oil for your vehicle. A Chrylser ac compressor takes entirerly different oil than a Suzuki XL7 Compressor. They simply are not interchangeable, you have to be exact.

You need lookup the AC oil chart and see what is required for your vehicle. Putting in too little oil can result in burning out the compressor bearings. Putting in too much oil can reduce the perfomance of the system. The wrong oil can also cause compressors to burn out.

So I’ve heard them term Locked Up AC Compressor plenty of times, but many people do not know what that actually is.

Essentially a compressor can lock up and stop turning if enough gunk gets trapped inside. The compressor has pistons (or scrolls, veins etc, etc depending on compressor) that spin, turning liquid feon into gas freon (the pumping action). The space for this freon is millimeters and particals can get trapped in these spaces causing them to not be able to turn. This is a locked up compressor.

Locked up compressors are often caused by ac black death, but even a little debris can lock up a compressor. The lesson is that any debris can be deadly to an a/c system when pressurised at 200+ pounds.

For Example the Suzuki XL7 is a notirious problem car. The Suzuki AC Compressor on this car is known for getting debris into the compressor and locking it up. On the XL7 and Grand Vitara the only answer is to replace the condenser because it cannot be flushed. Then you need to clean and flush the rest of the system.

In the middle of summer everyone is doing some ac compressor repair and installation right now. One of the important parts of the install is the evacuation of the old freon and contamination

The A/C system must be free of moisture and air to work properly. Removing the air and moisture
with an A/C system vacuum pump for 45-60 minutes is necessary to deliver proper and long lasting A/C performance.

Its hard to believe, but water based moisture is an ac system killer. In order for the auto air conditioning compressor to not leak or fail later on, you need to be 100% dry and that is why leaving the vacuum pump on longer is always better. Even a small amount of moisture is deadly.

Got a good question, what is AC Compressor Black Death?


Black death is caused when A/C Oil breaks down. A/C Oil is mixed in with the refrigerant to keep the air conditioning compressor lubricated. When it breaks down it causes the compressor, condenser and other parts to no longer be lubricated and thus overheat. The actual black ’sludge’ is actually a combination of solder flux from the condenser, alumninum from the compressor and other contaminants. This new ’sludge’ cools and hardens in various parts of the system. Notoriously the low side of the system including the condenser, orifice tube, expansion valve etc, etc.


It cannot be flushed out. Most of the system, including condenser, will have to be replaced. If you do need ac parts, visit our sponsor.