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  1. #1

    What are causes of a bad High Pressure Switch?

    I had a hvac tech come out due to no cooling.He said i need to replace my high pressure switch.

    1. what is the purpose for the switch?
    2. Do these typically go bad and why do they go bad?

    thanks in advance.

  2. #2
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    Quote Originally Posted by illuzionb18c1 View Post
    I had a hvac tech come out due to no cooling.He said i need to replace my high pressure switch.

    1. what is the purpose for the switch?
    2. Do these typically go bad and why do they go bad?

    thanks in advance.
    To shut off unit when system pressures get to high. Dirty condenser coil for one. To much cycling of switch could were it down. Had to replace one on a new roof-top unit. ( LEMON )

  3. #3
    Quote Originally Posted by VTP99 View Post
    To shut off unit when system pressures get to high. Dirty condenser coil for one. To much cycling of switch could were it down. Had to replace one on a new roof-top unit. ( LEMON )
    you mention too much cycling of the switch could cause it to wear down. I assume any cycling of this switch is a bad thing since that means there is high pressure(unlike say the contactor switch)?

  4. #4
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    Quote Originally Posted by illuzionb18c1 View Post
    you mention too much cycling of the switch could cause it to wear down. I assume any cycling of this switch is a bad thing since that means there is high pressure(unlike say the contactor switch)?
    Correct the switch is a safety device only. Most are auto reset but some come manual. Lucky for you its a auto or he would be back every time. Get him to fix the problem and not just change parts. Unless it was a lemon.

  5. #5
    Quote Originally Posted by VTP99 View Post
    Correct the switch is a safety device only. Most are auto reset but some come manual. Lucky for you its a auto or he would be back every time. Get him to fix the problem and not just change parts. Unless it was a lemon.
    ok, last question, and thank you for your help btw. So i dont get screwed over, i want to know the common causes for the high pressure switch going bad.
    you mentioned dirty condenser coils, i forgot to mention this is a geothermal unit. could low water in the water loop cause high pressures?

  6. #6
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    Switches can also just go bad............today's components are just not made as good as they once were.
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  7. #7
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    machines built by humans, sometimes they just break.

    most HP switches i see are manual reset so they do not cycle if there is a problem.

  8. #8
    Quote Originally Posted by t527ed View Post
    machines built by humans, sometimes they just break.

    most HP switches i see are manual reset so they do not cycle if there is a problem.
    im getting confused now. i understand parts break. but, from a previous post, this switch seems like it operates when there are high pressures in the system. therefore, it should 'normally' go bad if they are being 'used' correct?
    which means there is high pressure in the system correct?

    i dont understand how they are breaking if there is no high pressure in the system causing them to 'move'.

  9. #9
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    switches can go bad or become weak without ever seeing high pressure.

    can't see it from here and don't know what you're tech found but nothing suprises me anymore.

  10. #10
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    You're asking us for an autopsy report on a switch and situation about which we know nothing. Why does a headlight stop working? Why does a shoelace break? Sometimes things just wear out. Other times they just break. That's why new equipment has warranties. The warranty is there to provide the purchaser with some level of protection if a component fails prematurely. You were given some reasons why a high pressure switch might be called into service. Anything that causes the pressure in the system to exceed a limit set by the manufacturer would cause the high pressure switch to turn the unit off. Once the pressure dissipates, the HP switch normally automatically resets and the machine comes back on. If the HP switch fails in the 'open' position, the system never comes back on. Broken switch. Maybe the switch was broken from day #1 and the system never reached a high pressure condition, just the switch finally gave out. We can't tell that from here.
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  11. #11
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    switches in these systems are of two types, "control" switches and "safety" switches. control switches are designed and built to cycle millions of times in their lifespan, safety switches simply wait to change state in an emergency if you will. so its "possible" you have a head press. condition where your switch is doing what it should and failed for being cycled so much more than it was designed for.
    i was born under a wandrin star.

  12. #12
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    Why didnt you ask the tech that said your switch was bad? Bottom line as everybody said, it could be any of those reasons. A switch is still a switch no matter what the application (safety or control). If you stand there and flip your light switch on and off a 1000 times, either the switch is gonna go or your bulb will. Its a race. Try it.
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  13. #13
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    Quote Originally Posted by dna View Post
    Switches can also just go bad............today's components are just not made as good as they once were.
    If the high pressure switch never opened. It wouldn't go bad in the open position. Unless it was sensing pressure near its trip point for an extended amount of time.

    On a geo. There are about 10 to 15 reasons that the switch was opening.
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