Lennox XC14 A/C doesn't start and high pressure switch reset not working

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Old 07-08-15, 11:12 PM
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Lennox XC14 A/C doesn't start and high pressure switch reset not working

I have a 3 year old Lennox XC14 home air conditioner. I rarely use it because my area only need to run a few days per year. This year it doesn't work any more. I traced the 24V control signal all the way to high pressure switch input, but no 24V on its output. So, it should be the high pressure switch related problem. The puzzle I have is that the switch is still off when I press the red reset button on the switch. There is no clicking or locking sound when I press it. The switch is Sensata 39PSL012-439. So, I guess the switch must be broken. If I want to replace it, how can I do it? I have a concern that the liquid may come out when I remove the switch. Anyone has experience on this issue please help,
 
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Old 07-09-15, 10:00 PM
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Welcome to the forums.

I always check sensors with an ohmmeter to positively confirm their status.
I couldn't find that switch listed in Sensata's product listing.

I would need the full model number of the condensor unit for further assistance.
 
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Old 07-10-15, 07:25 PM
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Figured out the actual PN is: LENNOX 42W41 100103-03 Switch-High Pressure switch.

Thx
 
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Old 07-14-15, 08:53 PM
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I measured the resistance cross the two terminals with DM. It's open with infinite value no matter I pressed reset button or not. 100% sure the DM was working correctly.
 
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Old 07-14-15, 09:32 PM
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Based on the one picture I could find..... I'm fairly certain you will need to have the refrigerant removed before replacing that switch. That will require the services of an HVAC tech.
 
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Old 07-14-15, 09:58 PM
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http://www.amazon.com/Valve-CD9611-C...ords=C+D+valve



Name:  Adaptor Tee.jpg
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I would connect an adapter T to the high pressure port and connect a new high pressure switch to it. Just leave the existing high pressure switch installed and move the 2 wires to the new pressure switch.

Match the cutout and cut in pressure.
 
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Old 07-15-15, 10:18 PM
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Thx Huston204 and PJmax. I have concern if I remove the switch or add an adaptor, the liquid may leak out. Did this guy do the right thing? Can I follow his procedure to replace the switch?
https://www.youtube.com/watch?v=7z7PLhqQAlo
 
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Old 07-15-15, 10:29 PM
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If you follow Houston's method.... you will loose only a very tiny bit of refrigerant.

I can't comment on the video as I do not know if Lennox uses a schrader valve below the high pressure sensor.
 
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