HEAT PUMP ISSUE, contactor does not pull in, no 24v to it


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Old 03-01-11, 06:28 PM
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HEAT PUMP ISSUE, contactor does not pull in, no 24v to it

Hi, i am new here. First time messing with home hvac system. My heater stopped working one morning so i figured i could try messing with it. I normally work on cars, and know the basics of electrical so i thought it should be too hard. i found my heat pump motor was not spinning, it was getting power but just wont spin. so i took off the capacitor and brought to a local shop and they tested it and said it was bad. i changed it, the motor now works. But i noticed i wasnt getting any heat, so i checked the unit in the backyard. I didnt hear the fan blowing like normal so checked for breakers and fuses, all was good so i took off the cover to the unit. took a couple minute to look around for loose wires, anything that looked burnt, or broken. didnt see anything obvious so i continued on. i found the contactor, tried pressing it, the fan comes on. tested the coil wires for voltage, nothign there. i thought it was bad so i took it off and bench tested it, coil is working and pulled contacts when given power. so i put it back in and back tracked the wires, i found one that that can be the cause. have no idea what it is called, maybe a pressure switch of some sort.

on the contactor coil there are two wires, grn/yel is grounded and blue goes to this switch. when thermostat is turned on i get power from one side of the switch but not the other (which is connected to contactor. what is this switch and does it sound like the problem?

picture of said switch, one side have 24v when i turn on the heat, other side have 0v and that connects to the contactor. so im guessing this is bad?



i really hope i was clear enough, its my moms house and i can NOT afford to call someone out to look at it.
 
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Old 03-02-11, 12:53 PM
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push the button on the top of the switch in. Can't tell for sure if that is high pressure or low pressure switch, typically if this is tripped you have a refrigerant issue...........
 
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Old 03-02-11, 01:36 PM
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It is a high pressure switch, push the red rubber button on top to reset the switch, it has likely tripped because the fan motor was not running. good luck.
 
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Old 03-02-11, 02:52 PM
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i cant believe that was it. before posting this thread i did search, and i did attempt to press the top. but it didnt do anything. so i thought maybe its not the right switch. but after posting this and getting your responses, i held the pressure switch tightly and pressed the top and heard a click!!! it works perfect now. thank you for your help!!! much appreciated.

if you guys dont mind, can you explain what could have happened? im thinking my capacitor went bad over night so the fan didnt spin inside the house. because of this, the outside pump/fan kept going since inside thermostat reads alot lower then what i set it at. maybe this over heated the backyard unit causing switch to trip? i feel good that i helped my mom fix this without calling a pro over to do it!! thanks again everyone
 
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Old 03-02-11, 03:03 PM
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because you were in heating mode and your indoor fan stopped, this tripped the high pressure limit due to the pressure being higher from warmer refrigerant.
 
 

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