Results 1 to 9 of 9
  1. #1
    Join Date
    May 2014
    Posts
    10

    Low pressure switch fault?

    Thermostat keeps displaying error - "system in low pressure switch lockout."

    Apparently this is triggered when the low pressure switch is open for more than five seconds. What would cause that condition to occur?

    When the error pops up, the outdoor unit (York AC) refuses to come on. Only the blower/fan comes on. Pulling the thermostat from the wall (York Communicating Console) will cause the system to reset and it will begin operating normally again, for usually 12-24 hours. Then it trips again.

    First tech said coils were frozen. Turned on fan, turned off ac. Second tech said issue was probably blocked vent or dirty filter (?!?). Company hesitant to send tech if unit is frozen. Visible inspection this morning revealed no freezing issues.

    Is this something I can resolve on my own? Or is a tech necessary? System is only a few months old.

  2. #2
    Join Date
    Dec 2002
    Location
    Houston,Tx.
    Posts
    16,011
    Could just be a bad low pressure switch, if you can get a tech out, he can verify this pretty easy.


    Sent from my iPhone using Tapatalk
    __________________________________________________ _______________________
    “Experience is a hard teacher because she gives the test first, the lesson afterwards". - Vernon Law

    "Never let success go to your head, and never let failure go to your heart". - Unknown

  3. #3
    Join Date
    Oct 2012
    Location
    Wisconsin
    Posts
    3,865
    It could also be that the coil is freezing, but by the time you notice this, the system has shut off and thawed itself.

    If its happening consistently every 12-24 hours it shouldn't be too difficult for a tech to diagnose.

    You can check the obvious things yourself - is air filter dirty, all vents open, etc.

    If the system is only a few months old, the company that installed it should step up to the plate and figure out what's going on and fix it.

  4. #4
    Join Date
    Jun 2014
    Location
    Dover, DE
    Posts
    626
    Other then checking the air filter, this isn't really anything DIY. What air filter is being used?
    I'm a little concerned you've had 2 techs there and still haven't been able to fix the issue.

  5. #5
    Join Date
    Jul 2006
    Location
    Virginia
    Posts
    4,676
    need a better tech that will spend the time to repair it
    We really need change now

  6. #6
    Join Date
    May 2014
    Posts
    10
    Quote Originally Posted by Mike19 View Post
    It could also be that the coil is freezing, but by the time you notice this, the system has shut off and thawed itself.

    If its happening consistently every 12-24 hours it shouldn't be too difficult for a tech to diagnose.

    You can check the obvious things yourself - is air filter dirty, all vents open, etc.

    If the system is only a few months old, the company that installed it should step up to the plate and figure out what's going on and fix it.
    The system came with a 100% coverage contract for the first year.

    No returns or vents are blocked. I have not checked the filter to see its' condition. The thermostat has a filter change reminder built in, but it doesn't seem very reliable. It went off after just one month, which I thought was odd. I have it set for three months. I use the three month filters from Filtrete. The red allergen defense ones. But last time I picked up some of the purple healthy living ones. Was going to use one next time the filter reminder went off. Guess I am going to have to go in and check the filter myself.

    The system ran fine today, no error messages or anything. I will have to ask if they checked the pressure switch. I wasn't here when they were.

    Thanks to everyone for their suggestions.

  7. #7
    Join Date
    Oct 2002
    Posts
    1,328
    Probably, turning system switch off and on will reset computer, instead of pulling thermostat.

    May have an intermitant blower relay, but I would install a cheapo air filter to see if that eliminates your problem.

  8. #8
    Join Date
    Aug 2009
    Location
    Beatrice, NE
    Posts
    2,188
    You need someone to come in and test the sensors. I had a Trane with similar issues, found two sensors out of spec.

  9. #9
    Join Date
    May 2014
    Posts
    10
    They determined the low pressure switch was defective. Replaced it with a new one and system has worked flawlessly ever since.

    A little peeved that the tech who mentioned the filter (same one who came back and diagnosed and then repaired the system) didn't take the time to mention the filter was filthy. There were two brand new filters just sitting there in the utility closet, he could have at least changed it out.

    As for filters, I usually use the red Filtrete 3 month ones. We have multiple pets and I like to trap any dander and fur that I can.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event