Heat Pump Stuck in Defrost Mode- PLEASE HELP

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  #1  
Old 12-14-10, 08:29 AM
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Heat Pump Stuck in Defrost Mode- PLEASE HELP

I need your help to diagnose my heat-pump problem ( unit is RUUD Achiever 14 , 2003 install) . Last night temps dropped to 20 F in FL and I found our heat-pump stuck in defrost mode in the morning ( emergency heat was on and it maintained inside about 68 F or so ) . I decided to reset the system after waiting for about 2 hrs. for the defrost mode to go back to normal heating mode . I shut off the circuit brakers for 10 minutes and restart the system again. It appears to be running normal now .
I would like to hear from members as to how I should be diagnosing this problem . I do not know much about A/C and heat-pumps other than some limited therotical knowledge . I am thinking about 4 possible problem area :
1-Mulfunctioning “Defrost Board “
2-Bad “Outdoor coil temperature sensor” ( If there is such thing )
3- Bad reversing-valve selonoid
4- Stuck reversing valve
Would you guide me thru a diagnostic path . I have an ohm-meter if you tell me a detailed procedure, I should be able to follow . Your help is appreciated . Thank you
 
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  #2  
Old 12-14-10, 04:57 PM
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Guys , I need some help here .
1- I would like to check the reversing valve solenoid . What kind of value I should be getting with an ohm-meter ?
2- My owner's manual mentions a "test mode for defrost cyle" by shorting two pins . I would like to do this test to see if reversing valve is working . Where are these test pins, are they on defrost board ? what is the procedure ?
 
  #3  
Old 12-14-10, 06:23 PM
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test pins are on the defrost board they are for checking the defrost mode the reversing valve can get stuck if it does that again see if it has voltage to the reversing valve. what is the model # of the heat pump?
 
  #4  
Old 12-14-10, 06:43 PM
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gsn1971,
Thanks for your response .
System Ruud Achiever 14
Outside Unit Model # UPLA-041JAZ
1-Can you tell me what kind of media I need to jump those terminals with (alligator clips , etc? . Since the outside cover will be open , is there any interlocking switch that I should depress before jumpering ?
2- How do I check control voltage at solenoid ( would you give some details )
3- Also , if I have to electrically test the RV's solenoid wiring , what kind of ohm value I should be getting .

Thanks for your help
 
  #5  
Old 12-15-10, 03:37 PM
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I would like to have some more support . I checked the RV solenoid (with system on ) and 24 VAC was present at the coil . I replaced the solenoid for the hack of it , since I could not find a reliable test method for it. Now I am checking the system to see if it cures the problem. If not, I would like to trobleshoot the defrost board and any other component that has to do with governing the reversing valve (solenoid already changed ) .

Can anybody explain to me how I can test defrost board and how I should trace control voltage from defrost relay (possibly integrated into defrost board PC ) to solenoid .
Thanks
 
  #6  
Old 12-15-10, 04:08 PM
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if you do a google image of a reversing valve coil it will popup but i dont thank you have a problem with the coil it sounds like its working the reversing valve wont switch over with out it working. to make sure. turn the thermostat to cool let it run 5 min. (warmer air comes out of the heatpump) then back it heat (cold air comes out of the heatpump) most likily the reversing valve & coil is working if this happens. then thank about replacing the defrost board and the defrost senser we usually change both
 
  #7  
Old 12-15-10, 07:54 PM
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On most system the valve is installed so that with no power to the valve it will be in heat mode, If I am not mistaken Rheem and Ruud the valve is placed so that cooling is the default even if it has a relay to invert the 24 volt AC "O" signal. On Rheem and Ruud they also use a high voltage coil as opposed to 24 volts from the inside, so if the unit is in heating when unit power is removed it will revert to cooling instantly. Which means that on other systems there is no such thing as the reversing valve "reverting to cooling" or "going into heating mode" It will only go into cooling with a signal to the coil otherwise it is in the heating mode.Rheem/RUUD is a great brand love that the compressor and everything is protected from the elements.
 
  #8  
Old 12-16-10, 11:52 AM
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gsn1971- Thanks for your continuing support .

I would like more support to continue my diagnostic work . Yesterday I changed the reversing valve solenoid, it did not cure the problem. Here is the symptoms of my problem, heat pump is working fine throughout the day hours and after midnight ( presumably trying to get into defrost mode in the middle of the night) ,then staying in emergency heat mode forever . I had to reset heat-pump at the circuit braker around 2-3 a.m. ,then system goes back to normal again until following night . During these episodes, the thermostat has "ER " on it and no temps are shown , the outside condenser coil still blowing cold air as it is in heating mode .

gsn1971- I took your advice and switched the unit from heat pump mode into A/C mode . Thermostat did not give any system error and when the system was running in A/C mode I observed heat being discharged from outside condenser coils, as it should have been . Then , I switched back to heat mode , and it is running fine at the moment , during the day , as of I am writing this . This test leads me to believe that reversing valve is functioning .

What do I need to check at the next step ? defrost board ? coil temp sensor ? how do I check these .
Your help is appreciated .
................
I ran into some fresh info as I was going thru my Robertshaw model 1920 thermostat manual. It says " The thermostat controls the second stage emergency heat . Used only when the primary stage of heat is not functioning or requires service . The display shows EMER ( mine says ER ) when emergency heat is activated ".
Could it be that my problem is a bad electric heater coil ?
 

Last edited by Wolfboro; 12-16-10 at 12:26 PM.
  #9  
Old 12-18-10, 10:24 AM
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Since no new suggestion came up and I ran out of ideas for troubleshooting , I had the tech in to check the system . He found the charge a bit low ,added 2 lbs. , he checked both inside and outside coils for leak using a freon detector . He could not find any obvious leak . Since there has been a compressor change about 6 months ago under warranty ( 7 year old unit ) , he thinks either there is a slow leak somewhere or the previous tech did not charge it right , the time will tell which one . In the meantime I have to do my homework to identify a new brand and a source just in case I need it .

I am still a bit puzzled that why system did not work right during 15- 20 F overnight temperatures but worked fine above 35 F temperature . Any explanation ?
( reversing valve was checked and functioning OK)
 
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