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Discussion Starter #1
I have a 2007 mazda 6. The ac worked fine until the compressor locked up. I replaced the compressor and jumped the clutch ac works fine with the jumper in but will not work without it. Any help would be appreciated.
 

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I assume you charged it after replacing the compressor. Too much or not enough refrigerant can cause that. Purge a little bit at a time to see if it starts.
 

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Discussion Starter #4
Yes, I charged the system and still the compressor only works when I jump it. Blows nice and cold only when jumped
 

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Uh, please describe the procedure "replaced the compressor".... :)
I'm also interested on how he did it exactly. The ideal way of charging is by "weight" but all those technicians I've seen are basing from the high pressure gauge reading.

Yes, I charged the system and still the compressor only works when I jump it. Blows nice and cold only when jumped
Were you able to check the pressure switch?
 

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So there are two pressure switches on "American/Jap" design systems.

The low pressure switch is a safety cutout. It closes at ~30psi, it is on the low side, and if it is not closed the compressor WILL NOT engage. It is there to prohibit compressor operation if the charge level is ridiculously low OR the outside temperature is very low.

The high pressure switch is ALSO a safety cut-out. It is normally closed. It usually opens around 350-400psi, and if IT is open the compressor is ALSO disabled. It is on the HIGH side. If it is open, the compressor will not engage. It is there to cycle the compressor NORMALLY and, to prevent things from exploding (e.g. in the event of a blockage, etc.)

On some European systems there is ONE pressure transducer that measures BOTH high and low, on the high side (e.g. VW/Audi.) It is not a switch -- it is a transducer. You can figure out if you're dealing with such a system as you will see only ONE sensor and the plug will typically have three, rather than two, contacts. These work in combination with a variable displacement valve in the compressor -- some mechanical and some electrically-modulated. But US and Japanese systems tend NOT to be set up this way; they cycle on and off rather than being variable-displacement.

There is exactly ONE proper way to charge a modern TXV-equipped auto A/C system -- by weight. You need to replace the dryer JUST BEFORE pulling vacuum, you pull vacuum, you make sure it's good (e.g. no leaks) and then charge by weight. There is no other PROPER way to do it.

If you replace the compressor the new one will almost-always come with a full oil charge in it suitable for the entire system. You therefore MUST flush the system to remove all other oil AND pull vacuum to make sure there is NO residual anything in it. If you don't you'll be over-oiled, maybe dramatically so. You must also replace the dryer. You SHOULD replace all the O-rings, and they are fluorocarbon -- not regular buna rubber; if you use buna they WILL leak over time. In most cases if you're replacing the compressor you also should replace the TXV because it is likely contaminated. In addition ANY time you use the service ports (e.g. to charge, etc) on a system more than a few years old have a new set in your toolbox as they OFTEN fail to seal if older when you remove your gauges, and if that happens you're hosed if you don't have replacements. A set of replacements is $10 or so; keep a set in your toolbox.

If the pressure switch(es) are not working you need to replace them. Again, on a US or Japanese system there are usually TWO; the high side must be closed (less than maximum pressure) and the low side closed (more than minimum) or the compressor will not run. Jumping the compressor is VERY dangerous; those switches are there for a reason and bypassing them is extremely unwise.

Finally, NEVER work on or around a charged A/C system without gloves AND full wrap-around goggles. IF a hose or other seal bursts liquid refrigerant that WILL be ejected and will instantly freeze anything it comes in contact with. If that's your eye you will be instantly and irrevocably blinded and if your arm or hand you will be severely injured. No, I'm not kidding. Don't screw around with A/C systems without proper protective equipment. Ever.
 

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No, I'm not kidding. Don't screw around with A/C systems without proper protective equipment. Ever.
I've heard of a story where the guy instinctively plug the leaking refrigerant with his fingers. The guy suffered with half of his arm frozen. They were in the middle of the sea so it took them days before they arrived on the nearest port.

I have forgotten the whole story so I can't recall if his arm was amputated or not.
 

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Once again, purge some refrigerant out.
I once overcharged my system and fought if for a year before finding that it had too much in it causing the high pressure switch to shut off the compressor.
 
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