Air conditioner high pressure switch


  #1  
Old 08-16-18, 02:32 PM
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Air conditioner high pressure switch

Background :
  • Lennox XC-14, 3Ton Air Conditioner
  • Thermostat calls for cooling
  • Furnance blower starts
  • 24 V at air conditioner when cooling is called, but no voltage at contactor
  • 220 V at contactor
  • Capacitor, Contactor & Filter have been replaced.
  • Two different tech's visited and confirmed that the system is otherwise fine (pressure etc) and runs when depressing the contactor. No solid reasons otherwise why the A/C is not working. One tech confirmed the issue is with one of the sensors, but not a Lennox agent, so declined to continue. Second tech was junior and didn't know how to proceed.
  • Myself identified the problem with the pressure switch which always has an open circuit (see attached picture). A/c works when i bypass the pressure switch.
  • Unit is still under parts warranty
  • Waiting for senior A/c tech to visit in two weeks to confirm issue and provide a solution.
  • Found the below discussion on exactly this issue.
Name:  Broken Switch.jpg
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My Questions :
Q1. What would be a reasonable labor charge to replace the pressure switch ? I have to pay $140 for the diagnosis by the Senior tech.
Q2. Can myself as a homeowner replace the switch? I am comfortable doing the job, but not sure if there are other factors to consider.
Q3. Can I bypass the pressure switch and run the A/c for a week while waiting for the senior tech ?
 

Last edited by RyanCgetc; 08-16-18 at 02:48 PM.
  #2  
Old 08-16-18, 08:41 PM
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Can't really tell from your comments if you actually pushed the reset button (firmly) on top of the switch center.
 
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Old 08-16-18, 08:57 PM
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Welcome to the forums.

If the green hi pressure switch has a Schrader valve under it...... the job is easy. A Schrader valve is similar to the valve on a car tire. It's normally sealed and when the insert is pressed.... the valve is open. I've not changed one of those so I can't tell you what it has. If it's removed and it doesn't have a Schrader valve or if it gets stuck.... the charge will be lost. Not a good thing.

Could you bypass the switch and run the A/C..... sure but it will be without hi pressure protection.
If the air filter is clean and you have good airflow in the house and the coils are clean inside and out... it would be a minimal risk but I am not advocating it.

That part should be relatively inexpensive. I'd check locally for a service company to change it and forgo the parts warranty. You need someone that works on and knows Lennox.
 
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Old 08-16-18, 09:58 PM
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Originally Posted by 57TinkerMan View Post
Can't really tell from your comments if you actually pushed the reset button (firmly) on top of the switch center.
The reset was pushed by myself and both the techs who visited. No luck
 
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Old 08-16-18, 10:17 PM
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Originally Posted by PJmax View Post
Welcome to the forums.

If the green hi pressure switch has a Schrader valve under it...... the job is easy. A Schrader valve is similar to the valve on a car tire. It's normally sealed and when the insert is pressed.... the valve is open. I've not changed one of those so I can't tell you what it has. If it's removed and it doesn't have a Schrader valve or if it gets stuck.... the charge will be lost. Not a good thing.

Could you bypass the switch and run the A/C..... sure but it will be without hi pressure protection.
If the air filter is clean and you have good airflow in the house and the coils are clean inside and out... it would be a minimal risk but I am not advocating it.

That part should be relatively inexpensive. I'd check locally for a service company to change it and forgo the parts warranty. You need someone that works on and knows Lennox.
Yes, I have already bypassed safety switches and can run the A/c.

The filter is brand new and I always use a 3M filter. The coils were never cleaned in 8years, but other that the unit being dirty, the coils are very clean. I will also hose them with water

Finding someone to visit is getting tricky and everyone is busy and nobody wants to trust a homeowners diagnosis. Hoping the senior tech asks for a decent labor else I have to source the part and replace it DIY.

Thanks for the detailed response.
 
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Old 08-17-18, 04:22 AM
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Don’t use a 3M filter, they can restrict airflow too much and cause issues. The air filter isn’t meant to be a whole house air cleaner. It’s to keep debris out of the air handler.
Those manual reset high pressure switches can be difficult to reset. Needs a hard press straight down.
I wouldn’t run it bypassed, as you don’t know what caused it to trip in the first place.
It’s a simple fix unless someone has removed the core under the switch for some reason. Which I’ve experienced.
 
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Old 08-17-18, 07:47 AM
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Originally Posted by roughneck77 View Post
Don’t use a 3M filter, they can restrict airflow too much and cause issues. The air filter isn’t meant to be a whole house air cleaner. It’s to keep debris out of the air handler.
Those manual reset high pressure switches can be difficult to reset. Needs a hard press straight down.
I wouldn’t run it bypassed, as you don’t know what caused it to trip in the first place.
It’s a simple fix unless someone has removed the core under the switch for some reason. Which I’ve experienced.
Acknowledged on 3M filters. Which brand/model would you recommend ?

The Lennox XC14 has a service port right next to the compressor and gives easy access to pressure switch & thermal sensor. I am 100% sure it's a defective pressure switch, but will give it another try and report back.

I got the XC14 was installed in 2010 and nobody has messed with the unit. So, unless it came defective from the manufacturer, the core under the switch has never been touched and shouldn't be an issue.
 

Last edited by RyanCgetc; 08-17-18 at 09:52 AM.
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Old 08-17-18, 11:53 AM
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Those manual reset high pressure switches can be difficult to reset. Needs a hard press straight down.
Checked switched and looks solid and there is no play. Maybe it's stuck in one position
 
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Old 08-27-18, 10:41 AM
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Finally the senior tech visited and HVAC company confirmed the parts/labor. The tech bypassed the pressure switch and also found the Fan Motor vibrating and leaking oil. Now, I am waiting for parts to be sourced and tech to revisit to replace the parts.

Pressure Switch
Parts = $0 covered under warranty
Labor = $60

A/C FAN motor
Parts = $0 covered under warranty
Labor = $240

Fan motor labor of $240 seems to be very high as several videos show the job taking less than 15min. I was able to bargain them from the initial quote of $300 labor. They wouldn't give me the part, so only other alternative is to source the part for $187 and DIY labor. Doesn't justify the savings of $50.
 
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Old 08-27-18, 10:53 AM
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Be sure the fan motor includes the correct sized cap if it's not a 100% OEM replacement motor.

$240 is a little high but it can take more than 15 minutes. The blades are going to be stuck on the motor and need to be freed. If they install the parts there is still some warranty available.
 
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Old 08-27-18, 11:11 AM
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Originally Posted by PJmax View Post
Be sure the fan motor includes the correct sized cap if it's not a 100% OEM replacement motor.

$240 is a little high but it can take more than 15 minutes. The blades are going to be stuck on the motor and need to be freed. If they install the parts there is still some warranty available.
Don't understand what is "correct sized cap". Can you please clarify ? is that something like below link?
https://www.repairclinic.com/PartDet.../32621/2711105

The motor should be sent from Lennox, so not too concerned about sizing, but agree with you on the warranty angle.
 
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Old 08-27-18, 11:14 AM
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Cap = capacitor for the motor
 
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Old 08-27-18, 11:24 AM
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Originally Posted by PJmax View Post
Cap = capacitor for the motor
Understood and thanks for clarifying.

I already replaced the dual capacitor for FAN & Compressor earlier this month.
 
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Old 08-27-18, 11:35 AM
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Yes..... I know that.... but the cap value MUST match the new motor requirement.
 
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Old 08-27-18, 11:58 AM
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What Pete is saying is that unless the new motor is an exact replacement (same make/model), it's possible that the new motor may require a different value capacitor than what the old motor used, and would have to be replaced with the correct value.
 
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Old 08-27-18, 12:07 PM
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Thanks for clarifying about capacitor. I will check the fan motor before they install.

Hoping they don't bring a different motor and try charging me $160 for the capacitor. That was their quote in April to replace the capacitor.
 
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Old 09-12-18, 08:47 AM
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Yah! The pressure switch was finally replaced this morning with the newer version which doesn’t have a reset button.

Sadly, one of the screws on the new FAN motor was broken, so they have to order a new motor. The CAP value for the new FAN motor matches the existing CAP.

Glad that the A/c is operational and safe again. Thanks everyone for their inputs and help.
 
 

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