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Low Pressure Side Of A/c System Going Into Vacuum


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#1
bigrevkev

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I have a problem with the A/C on my 2001 626. My mechanic did some diagnosis today & determined that at startup, the high and low pressure sides of the system are OK, but once the engine rises to normal operating temperature, the low pressure side goes to vacuum.

They suggested 2 possible causes:
1) Header plate in the compressor is worn or faulty
2) Faulty Tx valve

Can anyone suggest any ways to test these to try and determine which is the most likely cause?

If there is no easy way to test, does anyone know of a history of either of these failing (i.e. which do people think is the more likely cause)? I've owned the vehicle since new, and the only time the A/C has been worked on was 2 months ago when it was re-gassed.

Otherwise Murphys Law will mean whichever one we decide to try fixing first will be the wrong one http://www.mazda626....tyle_emoticons/default/smile.gif

thanks!

#2
Tranquility

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I'm not an expert, but my money is on the Thermal Exansion (Tx) valve being partially clogged. For the compressor to pull a vacuum, it has to be in good shape and there has to be an obstruction in the system. Wrong time of year, but does the Evaporator cool? What is the high side pressure. With a clogged Tx valve, high side pressures will be high unless the freon charge is low. I don't know where the Tx valve is located right off hand, but I would go after it first. Sincerely, Mr. Murphy http://www.mazda626....tyle_emoticons/default/biggrin.gif

#3
snailman153624

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The '98+ 626 uses an orifice tube, not an expansion valve IIRC.

Honestly, it sounds to me more like there simply isn't enough refirgerant in the system.

#4
bigrevkev

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For the compressor to pull a vacuum, it has to be in good shape and there has to be an obstruction in the system.


My mechanic & I independently came to the same conclusion as well. The Tx valve was replaced yesterday, and it seems to have fixed the problem. Of course, the Australian summer has now decided to be unseasonally cool, so I'll be interested to see how it behaves come the next heatwave - but it is already a marked improvement.

I hope this info will be of help to others. Thanks for the replies!

#5
ZoomOn

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The '98+ 626 uses an orifice tube, not an expansion valve IIRC.

Honestly, it sounds to me more like there simply isn't enough refirgerant in the system.


Does anyone know where the orifice tube is located in a 98 626 LX w/2.0L? Is it in the evaporator (under the dash) or in the high pressure line by the shock tower (or somewhere else??)?

I suspect I have a similar problem and I'm hoping I don't have to tear into the dash... fingers crossed.

#6
97Mazda

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It's in the small cooler pipe (between the accumalator tank and the compressor)

#7
hant9925

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Just curious if anyone has tried Interdynamics refrigerant. I read in a thread here that the quick release adapters doesn't fit Mazdas

#8
ZoomOn

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It's in the small cooler pipe (between the accumalator tank and the compressor)


Great!... I don't have to tear the dash apart which should make this repair much easier.

Thanks for the info.

#9
snailman153624

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You shouldn't need adapters, as your car is already R134a stock.




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