The compressor is missing the connector that turns the clutch on. The 2 connectors that are near it have a different connection type. When I press the ac button one of them gets 12V. However, when I look them up on line the connectors look like a high or low pressure connector. Do I simply need an adapter cable or are these the wrong ones.
Year & Model of truck please?
That's a ringer, Roger.
Huh?
Is that a roger, Ringer?
Huh?
(I'm very poorly misquoting one of the Airplane moves from the 1970s, this was flight deck dialogue. It's not very funny, unless you remember the movie, and even less funny if you do remember.)
Christopher A. Young Learn more about Jesus
Sorry, it's a 1995 chevy tahoe . When I bought the truck it had another compressor put on it and the old one thrown in the back. The connector on the old one is a din type so I found the wire to it. I'll need to put a blade type connector on that one. The other connector goes to the High pressure switch that is broken off on the new compressor. just a little tube sticking out now. No refrigerant in system so I am assuming it leaked out the HP switch. I took the snap ring off the old compressor HP switch, but I'm not sure if I can pull it out without breaking it. I noticed they had bared the wires on the low pressure switch and twisted them together so I need to fix that. Does the HP switch screw or pull out. I guess they are cheap so if I break it it's no big deal.
This is Roger, Ringer. There seems to be a lot going on here with this job. This system was "Mickey Moused" b4 you bought the truck so you have your work cut out for you if you really want to have a working A/C system on your truck. I hold a MVAC certification, and if you came into my shop, I would tell you that this would cost a ton of money to do it properly and most likely decline the job if you wanted to do it on the cheap.
That being said, I will try to offer my advice to keep your costs down since I assume you are using your own labor. My first step would be to seal the AC hose to compressor connection. I use a thick aluminum plate with a piece of rubber placed between the plate and the hose connection to seal the ports. Then I would pull a vacuum on the system to see if it is really air tight. If it leaks down and you have your heart set on having a working AC system, Be prepared to do a lot of work and/or spend money changing out parts or sell the truck and buy one that has a working AC. It could be cheaper.
If and only if the system holds a vacuum for several hours I woud start buying parts to finish the job. After flushing the system, I would replace the original fixed orfice tube with a variable orfice tube (about 40 bucks) This will greatly improve your low speed/city cooling. Always remember to lubricate the new o-ring seals you bought with fresh compressor oil before assembly otherwise they will leak, I guarantee it. After doing all of this it is time to install your new stock electrical connections and new or professionally rebuilt/with warranty AC compressor. I would NEVER trust an AC compressor that has been open to the air for more than a few days. NEVER. Rebuilt compressors for your truck start at about
200 bucks and go up from there. Fill the compressor with the right amount of the right oil ( probably 150 pag) and pull vacuum on the system again and charge it up to specs. All of this is assuming you have or can borrow/rent the tools to do the job and you know how to use them. You may have to show a MVAC cert. card to rent the tools. If you do not have access to the proper tools, you can expect to pay up to $1,800.00 to have it done if the evaporator and/or condenser need to be replaced. I know this is not what you wanted to hear, but it is what it is. Good Luck, JR
What's your experience been on the variable orifice tubes? I'm guessing it's been ok since you recommend them. I did a repair on my
92 explorer and when I went to the AC parts place I asked about a variable orifice tube and they talked me out of it. They said more often then not they didn't work right and had to be replaced and recommended I stick with the fixed orifice so I did.I am assuming that you have an AC system that has been converted from R-12 to R-134a. Factory R-134a systems generally work at a higher pressure than R-12 systems, yet a converted system still uses the older compressor thus operates at the lower pressure. Converted systems seem to suffer the most at lower engine speeds so a smaller or variable tube is a must if the customer is going to be happy. The only time I had a problem with a VOT was on a converted system that eventually pushed crap from the system into the tube (Yes I did flush the system), and the tube got stuck in the open position. Fixed tubes come in different orfice sizes and are color coded if you just want to put a smaller tube in your converted system. Fixed tubes are only a few dollars. Hope this helps. Regards, JR
Yes, higher pressure is very relevant. R-134A has a higher pressure because it is not as efficient as R-12, period. An AC system designed to use R-134A has a compressor that creates the necessary higher pressure. The higher pressure is required to achieve the required pressure drop in the orfice tube to get the desired cooling effect. Refrigerants do not carry heat. They are compressed into a liquid, then passed through an orfice tube or other device that quickly drops the pressure thus dropping the temp and creating lack of heat (cold) which flows through the evaporator and is transferred to the air passing through to the cabin. At this point in the cycle the refrigerant is mostly a gas that is then sent through a condenser, recompressed into a liquid, and starts the cycle over again. The system requires a SMALLER orfice to create the larger pressure drop needed at the lower compressor pressures created by city driving or idling. You have it exactly backwards, Stormin, but you are not alone. It's called the "Combined Gas Law", and I wish I could recover the time I've spent explaining it with this very simplified version to customers who want to understand. Regards, JR
Yes, higher pressure is very relevant. R-134A has a higher pressure because it is not as efficient as R-12, period.
CY: R-134a has a higher pressure at certain temperatures, because that's the properties of the material. Not "because it is not as efficient". Hint: google something called a pressure temperature chart.
An AC system designed to use R-134A has a compressor that creates the necessary higher pressure. The higher pressure is required to achieve the required pressure drop in the orfice tube to get the desired cooling effect.
CY: The higher pressure is necessary because the chemical has a higher pressure at certain temperatures. In a saturated system, that is.
Refrigerants do not carry heat.
CY: I'm on Planet Earth. Where are you?
They are compressed into a liquid, then passed through an orfice tube or other device that quickly drops the pressure thus dropping the temp and
CY: Ideally, the increased volume of the tubing allows shift from liquid to vapor, after the expansion device.
creating lack of heat (cold) which flows through the evaporator and is transferred to the air passing through to the cabin. At this point in the cycle the refrigerant is mostly a gas
CY: Ideally, it's mostly a liquid at the start of the evaporator.
that is then sent through a condenser, recompressed into a liquid, and starts the cycle over again.
CY: Where are you getting this nonesense? You have things way out of order. Go back and read the books again. You say "Condensor, compressor, liquid" which is not the correct order. Do study harder, and try to get the order right.
The system requires a SMALLER orfice to create the larger pressure drop needed at the lower compressor pressures created by city driving or idling.
CY: The 134A system needs a larger orifice, because the refrigerant is less efficient.
You have it exactly backwards, Stormin, but you are not alone.
CY: Odd, I was just saying the same about you.
It's called the "Combined Gas Law", and I wish I could recover the time I've spent explaining it with this very simplified version to customers who want to understand.
CY: I wish you would go back to school, and try to get it right, this time. Preferably before you misinform any other customers.
Regards, JR
Have a glance at that web page, and tell me (you can't, I 'm sure) how the combined gas law applies to an AC system with a single mollecule gas, such as R-134a.
Christopher A. Young Learn more about Jesus
It's called the "Combined Gas Law", and I wish I could recover the time I've spent explaining it with this very simplified version to customers who want to understand. Regards, JR
Here is a web page, you might be able to get the correct order of parts.
You have a lot to learn.
Christopher A. Young Learn more about Jesus
At this point in the cycle the refrigerant is mostly a gas that is then sent through a condenser, recompressed into a liquid, and starts the cycle over again.
HUH!!! That is exactly what they do. They pass through the system and carry heat from the evaporator out to the condenser.
They are compressed into a liquid, then
They do not "create cold" They absorb the heat from the air. This is the common reaction of refrigerants during the phase change from liquid to gas.
You are correct that the majority of refrigerant leaving the evaporator core is a gas. That is because it changes state from a liquid into a gas inside the evap. core. (Amazingly it EVAPORATES from liquid to gas)
Then the now hot gas goes through the compressor. The compression of the gas makes it denser and heats it more. Now it travels into the condenser core which removes the heat and allows the gas to condense from a gaseous state into a high pressure liquid. Then the liquid passes into the receiver/receiver-drier where it removes any water vapor or contaminants which may have gotten drawn into the system through any seals. It also collects liquid refrigerant so that any remaining gas can condense out.
The liquid now passes through either an orifice tube or a TXV (dependent on the system design) The purpose of either one is to regulate the flow and pressure of liquid refrigerant into the evaporator core. The idea of both is that given a working pressure and temperature of the liquid it allows only enough into the system that it can ALL convert to a gas and extract the heat. The TXV is MUCH better for this but it is also more expensive. Either way the liquid exits the metering device and begins changing into a gas as it extracts heat.
In the event you are using an orifice tube you will also need an accumulator. This allows any liquid that makes it through the evap. core to collect and prevents it from entering the compressor.
Any material that will change state from a solid to a liquid or liquid to a gas at a temperature lower than the desired cooling temperature can be used as a refrigerant. Some are much more practical and cost effective than others. For instance you can compress carbon dioxide from a gas to a liquid to a solid and it makes a dandy refrigerant. It is also not easy to deal with when it comes to the environmental regulations. Propane is another one that works well. However it doesn't play well when mixed with air and heat. The results can be really spectacular...
Water can also be used, However the solid to liquid phase is the only one with a temperature low enough to be practical for air conditioning in a vehicle. The conversion temperature to steam is a little higher than folks would like to have inside the cabin. It works well in evaporative cooling but you also require a continuous supply of water to replace the amount that is lost. Not real practical for a vehicle. However it does carry heat rather well and as such is used to cool the engine. However it is kept under pressure to prevent it from converting to a gaseous state.
Thanks, Steve. That's a lot closer to my understanding. compared to JR.
Christopher A. Young Learn more about Jesus
HUH!!! That is exactly what they do. They pass through the system and carry heat from the evaporator out to the condenser.
They are compressed into a liquid, then
They do not "create cold" They absorb the heat from the air. This is the common reaction of refrigerants during the phase change from liquid to gas.
You are correct that the majority of refrigerant leaving the evaporator core is a gas. That is because it changes state from a liquid into a gas inside the evap. core. (Amazingly it EVAPORATES from liquid to gas)
Then the now hot gas goes through the compressor. The compression of the gas makes it denser and heats it more. Now it travels into the condenser core which removes the heat and allows the gas to condense from a gaseous state into a high pressure liquid. Then the liquid passes into the receiver/receiver-drier where it removes any water vapor or contaminants which may have gotten drawn into the system through any seals. It also collects liquid refrigerant so that any remaining gas can condense out.
The liquid now passes through either an orifice tube or a TXV (dependent on the system design) The purpose of either one is to regulate the flow and pressure of liquid refrigerant into the evaporator core. The idea of both is that given a working pressure and temperature of the liquid it allows only enough into the system that it can ALL convert to a gas and extract the heat. The TXV is MUCH better for this but it is also more expensive. Either way the liquid exits the metering device and begins changing into a gas as it extracts heat.
In the event you are using an orifice tube you will also need an accumulator. This allows any liquid that makes it through the evap. core to collect and prevents it from entering the compressor.
Any material that will change state from a solid to a liquid or liquid to a gas at a temperature lower than the desired cooling temperature can be used as a refrigerant. Some are much more practical and cost effective than others. For instance you can compress carbon dioxide from a gas to a liquid to a solid and it makes a dandy refrigerant. It is also not easy to deal with when it comes to the environmental regulations. Propane is another one that works well. However it doesn't play well when mixed with air and heat. The results can be really spectacular...
Water can also be used, However the solid to liquid phase is the only one with a temperature low enough to be practical for air conditioning in a vehicle. The conversion temperature to steam is a little higher than folks would like to have inside the cabin. It works well in evaporative cooling but you also require a continuous supply of water to replace the amount that is lost. Not real practical for a vehicle. However it does carry heat rather well and as such is used to cool the engine. However it is kept under pressure to prevent it from converting to a gaseous state.
Ok, I bow to your superior knowlege. Regards, JR
Nothing superior about it. Just the way the system operates for just about all phase change refrigeration systems.
I appreciate the comment Steve. I did inadvertently place the condenser in the low side and stating in this forum that refrigerant doesn't carry heat was simply stupid on my part. Remember I was trying to put into writing something similar to what I told my customers. (A common customer comment was "how can you make something cold by taking something away, don't you have to add cold?") I don't usually describe the function of the accumulator to my customers as their eyes start to glaze over and I want to keep their interest to help them understand a little more than they do. Often when I told them that their cold air is the result of boiling refrigerant in the evaporator they look at me as if I have three heads and two of them are bleeding.
I do however stand by my statement that at lower city driving speeds or at idle a smaller orfice will help keep the cabin air cooler precisely because it DOES allow more refrigerant to circulate thru the system. In fact many city fleet vehicles such as taxi cabs and police cruisers are equipped with smaller orfice valves than vehicles that spend their lives mostly on highways. I know that you understand why this is so. I will let Stormin figure it out by himself. He's a smart guy and if he thinks about it for a while it will come to him.
I am also sure that you know that the so called combined gas laws refer to the mathematical combination of both Boyles law and Charles law to show the relationship of the variables of both laws and how they can be used.
I respect your knowledge as well as your opinion Steve, and if you have noticed you are the first guy I go to if I can't skull out a problem by myself. Warmest Regards, JR
If you wish, Steve or I can write some text you can read or speak to your customers. I can make the "boiling in the evaporator" bit some what more clear.
Christopher A. Young Learn more about Jesus
Slower speeds or idling. Lower RPM, and therefore lower ability to circulate refrigerant. This was a problem with some of the earlier R-134a systems.
Smaller orifice, means less refrigerant, more superheat, and less ability to cool the vehicle.
Smaller orifice means less refrigerant.
I invite you to explain it to me.
Christopher A. Young Learn more about Jesus
I do however stand by my statement that at lower city driving speeds or at idle a smaller orfice will help keep the cabin air cooler precisely because it DOES allow more refrigerant to circulate thru the system.
In fact many city fleet vehicles such as taxi cabs and police cruisers are equipped with smaller orfice valves than vehicles that spend their lives mostly on highways. I know that you understand why this is so.
I will let Stormin figure it out by himself. He's a smart guy and if he thinks about it for a while it will come to him.
MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.