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Old 07-28-2021, 09:25 PM   #1
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Join Date: Dec 2016
Location: Boston MA
Default 240 AC system woes

The AC in my 92 240 wagon is causing me sadness. It works for about 1 cycle then won’t come back on. If been trying to verify that the pressure switch at the drier is bad or sticking.

-if I tap the switch the compressor cycles on
-whenever I test the switch for continuity it is always closed
-if the connector is jumped the compressor runs smoothly
-pressure in the system seems ok, around 80 psi with the compressor off and high 30’s when it’s running

Is there any other switch or weak point in the system I should check before opening the system and changing the switch?
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Old 07-29-2021, 09:17 AM   #2
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Location: Boulder CO

There's normally a schrader valve in the switch port of the accumulator/dryer so that you can change the switch without losing much refrigerant. I have no idea how well they work after many years of being held open by the switch.
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Old 07-29-2021, 09:22 AM   #3
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Which side are you getting that pressure reading from? Either way, that is not what you want to see.
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Old 07-29-2021, 08:01 PM   #4
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Measuring at the low side port on the drier.

What are normal pressures? This is an R12 system that has been converted to R134
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Old 07-29-2021, 08:50 PM   #5
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Location: Ellijay

80 static, 30 running is not far off expected.

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Old 07-30-2021, 04:32 PM   #6
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I had one like that. First I suspected the connector was dirty. After cleaning and tightening the connector I patted myself on the back because it seemed to work again. For a day.

Next, I put a test light across the terminals of the switch. The light would be off when the compressor was engaged. It would flicker on when it quit cooling, and off again when tapped on the pressure switch. I didn't even hear a puff when I pulled the old switch to replace it with a new one. Omitted the pat on the back for the rest of the season. Nothing like self-congratulation to jinx a fix.
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