How do I test an expansion valve

mrp78 on Tue December 10, 2013 7:42 AM

How can I test an expansion valve? Can I test it on the car? Does the car have to be running with the a/c on to test?

94RX-7 on Tue December 10, 2013 8:02 AM

Quote
Originally posted by: mrp78
How can I test an expansion valve? Can I test it on the car? Does the car have to be running with the a/c on to test?

Very carefully. Sometimes. Yes.

If it is the type with a bulb, and you can access the bulb with the system in the car, then you can put the bulb in ice water and see if the low side pressure decreases. I've also read that you can dump liquid refrigerant on the disc where the control diaphragm lives and accomplish the same result.

If you can't access any part of the TXV with the system fully installed, you're just going to have to make an educated guess based on the pressures and temperatures you're seeing. Low side in a vacuum is frequently indicative of a bad TXV....but it can also be caused by a severe restriction in the system. I had a bad TXV earlier this year. System was producing a little bit of cooling, but the low side pressure was down around 15 PSI and the low side line was warm to the touch. The TXV wasn't metering in enough refrigerant.

Edited: Tue December 10, 2013 at 8:08 AM by 94RX-7

Jag987 on Wed December 11, 2013 12:00 AM

I know it was said that it had just been read, but how one someone pour liquid refrigerant on something if the wanted to. It just seems as soon as it is no longer under pressure, or not under very much, the refrigerant would turn to gas making it impossible to pour.

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I bought a can of 134a at w**-mart that had a stop leak, oil, and dye in it. It also had a hose and a gauge, so now I'm an AC pro!

94RX-7 on Thu December 12, 2013 7:20 AM

Quote
Originally posted by: Jag987
but how one someone pour liquid refrigerant on something if the wanted to

Invert a 30# cylinder such that the valve is pointing downward and open the valve and you'll get plenty of liquid out.

Jag987 on Thu December 12, 2013 5:14 PM

True, but that would be considered venting and is illegal. But it would work.

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I bought a can of 134a at w**-mart that had a stop leak, oil, and dye in it. It also had a hose and a gauge, so now I'm an AC pro!

mrp78 on Thu December 12, 2013 6:58 PM

Quote
Originally posted by: 94RX-7
Quote

Originally posted by: mrp78

How can I test an expansion valve? Can I test it on the car? Does the car have to be running with the a/c on to test?

Very carefully. Sometimes. Yes.

If it is the type with a bulb, and you can access the bulb with the system in the car, then you can put the bulb in ice water and see if the low side pressure decreases. I've also read that you can dump liquid refrigerant on the disc where the control diaphragm lives and accomplish the same result.

If you can't access any part of the TXV with the system fully installed, you're just going to have to make an educated guess based on the pressures and temperatures you're seeing. Low side in a vacuum is frequently indicative of a bad TXV....but it can also be caused by a severe restriction in the system. I had a bad TXV earlier this year. System was producing a little bit of cooling, but the low side pressure was down around 15 PSI and the low side line was warm to the touch. The TXV wasn't metering in enough refrigerant.

No way to test with the system off?

JoshuaSulwer on Sun August 09, 2015 3:37 PM

How about having access to the lines. I heard the low side should be cold and the high side should be hot, but I don't know much of anything (yet). What I do know is my low side line is luke warm going to the expansion valve and the high side line coming out of the expansion valve is ice cold going to the drier which is ice cold too, then the high side line from the drier is super hot. My AC is not blowing cold and only have the low side gauge and says zero psi, add a few ounces of 134 and the low side line gets cold, pressure fluctuates from 45psi to 80psi as clutch comes on and off, then when I start accelerating the 134a shoots out the relief valve..? I also I know I have looked at about 50 related and semi related blogs and videos and noone answers the questions about expansion valve or seems to have the problem I have, but I bet there is millions of people that use the low side only charging hose and gauge and a good handful must of had this happen... HI?

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Thank you