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Old 07-21-2021, 06:38 AM   #1
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A/C low pressure cutout switch

I am trying to find out more info about this pressure switch. It appears that it overheated and melted the wire loom at some point. I want to try and buy a spare for my trip next week and I am having trouble with a couple of things.

1. Can this switch be replaced without draining down the system? Is this screwed into a shrader type valve?

2. Is there a way to test this with a multimeter?

3. How critical are the on off points? This switch is 10 psi open, 40 psi close. I can find some close but not exact.

Thanks!
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Old 07-21-2021, 07:17 AM   #2
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Looks to me like all that melted is the plastic loom material they use to dress the wiring up.

The switches can normally be replaced without losing any charge. But I would recommend finding the service manual for the chassis your working on.

The only way to test the switch is to remove it and apply the specified pressures to see if it opens and closes at the appropriate pressures. You can jumper between the two wires to see if the compressor clutch engages - but all that tells you is either the switch is bad or your low on refrigerant (I would suspect the latter before the former, but if you let the compressor run for 2-3 minutes, if the unit isnít cooling then youíll know itís likely because itís low on refrigerant).

For the switch PSI ratings, find a switch with the same or higher cut-out (low) PSI, and the same or lower cut-in (high) PSI. But it surprises me that there isnít a cross reference replacement for your chassis.
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Old 08-02-2021, 09:09 PM   #3
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I ended up finding a pressure switch that was 4 psi to 34 psi. Its not a perfect match but it got it working! I will swap it later but i was in a time crunch before we headed out of town. A/C has been working great so far!
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Old 08-03-2021, 07:21 AM   #4
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Good you got it going! I would be a little concerned about the 4 psi cut-out because that signals too low of refrigerant, and running too low will limit refrigerant velocity and thus oil return back to the compressor.

Another approach would be to get two switches, one for each pressure point, and wire in series connected to that port with a tee. I realize it looks Rube Goldberg, but better to look that way than to trash an A/C system.
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Old 08-04-2021, 05:01 AM   #5
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The real question is why the wire overheated in the first place.
The switch didn't do it.
Too much current running through the wire.
A short downstream?
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Old 08-04-2021, 06:46 AM   #6
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Thanks for the feedback, yeah I was a little worried about it being too low. I will swap it with a proper psi one later. I can order one on the internet's
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