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  1. #1

    Confused Request for additional trouble shooting leads

    Hi,
    I am a home owner with a 16 yr old Lennox 5 ton rooftop combo heater/AC model GCS16R-651-75-3P. I am dealing with a loss of cooling after about 45 minutes of running. Three separate visits by professional A/C service have resulted in doing the following:

    1) replaced contactor for compressor and one discolored terminal
    2) replaced compressor capacitor
    3) replaced evap fan motor and cap

    After each visit, the unit was running well with a 20+ degree difference in return air and exit air in the house. After 35 to 50 minutes, the cool air stopped although the evap fan and the house blower continued to run .

    Each time the service men came out they checked freon pressures, amp draw on the compressor, resistance on the compressor motor leads etc. and said all was OK.

    The service men do not seem to have any strong leads on what to test next and its getting a bit expensive.

    Does anyone have any suggestions for further testing?
    Does any one know what temperature I might find on the external shell of the compressor that would cause the thermal switches in the compressor to trip? I would like to know if it is getting hot enough to trip or if it is below where one would expect the thermal protection to kick in.

    Appreciate any help or ideas ...

  2. #2
    Join Date
    Jan 2007
    Location
    TN
    Posts
    49
    Get another tech that will actually stay and troubleshoot the system. I have one of the old Lennox HP systems that had a bad TXV, the power head had partially lost its charge and exhibited these very same symptoms. At first my tech swore up and down that there was moisture in the system and it was freezing at the valve, which it would freeze after it ran and cooled well for about 30 minutes, so I was thinking that made good sense to me. Evacuated installed new filter drier recharged and it did EXACTLY the same thing, he messed with the sensing bulb stuck it in water and it choked down stuck it in hot water and it seemed to open up for a while but apparently after the entire sensing bulb line and all was cooled by the evaporator air there just was not enough charge to open the valve, the compressor would be starved of its life giving refrigerant that keeps it cool and it would kick off (right at the point where you could fry a egg on top). The guy stuck right there with it (he was good) it works better than it ever has now after the TXV was replaced. You got to get a GOOD tech, the little nervous guy that will only stay a few minutes is not gonna be able to help you with this.

  3. #3
    Join Date
    Feb 2008
    Location
    Western NC
    Posts
    2,504
    I hope they did not charge you for each visit.

    you say the tech checked pressures. But did the tech also check superheat and subcooling. That is the only true way to tell what a system is doing. A 20 temp difference. Where was that taken? if it was taken at your return and supply registers, then thats a little high IMO.
    I fully support the military and the War on Terrorism.


    If you don't know, then don't do. If you don't know and still do, then be prepared to pay someone else a lot to undo what you did and then do it right.

    If you do know, then do. But do it right. Otherwise, you may not be doing it long.

  4. #4
    Join Date
    Nov 2004
    Location
    North Carolina
    Posts
    443
    You need a different service company. Since you know how long your unit will run before it goes out, have the tech give you a call when he's about 20 minutes from your door and start your unit then. That way he will be set up and be able to see what happened to stop the comp. Easier on him and your billfold.

  5. #5
    Join Date
    Jan 2007
    Location
    TN
    Posts
    49
    A GOOD tech can pinpoint the problem for you especially if he has access to the previous repair history. Your problem may be something completely different from mine I just wanted to relay what happened to mine as the symptoms were similar and it took a while for a proper diagnosis and repair.

  6. #6
    Tsubaki - thanks for the post, the subject of the TXV was never mentioned in my discussions with the techs. I'll have to decide if I go back with the HVAC company and the two techs I've been working with or maybe try someone new ... in any case I'll know enough to ask the question. Is there any way the TXV can be tested/replaced without draining the freon?

    Iraqvet - They sure do charge for each visit .. plus parts. When this is over I may go back to the company and ask them to review the whole mess and perhaps negotiate a partial refund. Bottom line is if I call them in and they tell me it is $80 to knock on my door no matter what they do I figure I probably have to pay.

    On the "check superheat and subcooling" I do not know if they did that ... they reported that all the temperatures and pressures were OK. Would those be the temperatures on either "side" of the TXV that Tsubaki mentioned?

    The temperatures I mentioned were from the duct work inside the house ... I've put up thermometers at the air intake and at one of the vents right under the HVAC unit so I can monitor things inside the house. the tech took all their temperatures at the unit up on the roof.

    Model M Man - Good idea ... I'll see if I can get them to do that ... be just my luck that it will take an hour and a half next time to shut down.

    Many thanks for the suggestions ... might even have a chance with my next service call !

  7. #7
    Join Date
    Feb 2008
    Location
    Western NC
    Posts
    2,504
    Quote Originally Posted by Sacniteowl View Post
    Tsubaki - thanks for the post, the subject of the TXV was never mentioned in my discussions with the techs. I'll have to decide if I go back with the HVAC company and the two techs I've been working with or maybe try someone new ... in any case I'll know enough to ask the question. Is there any way the TXV can be tested/replaced without draining the freon?

    Iraqvet - They sure do charge for each visit .. plus parts. When this is over I may go back to the company and ask them to review the whole mess and perhaps negotiate a partial refund. Bottom line is if I call them in and they tell me it is $80 to knock on my door no matter what they do I figure I probably have to pay.

    On the "check superheat and subcooling" I do not know if they did that ... they reported that all the temperatures and pressures were OK. Would those be the temperatures on either "side" of the TXV that Tsubaki mentioned?

    The temperatures I mentioned were from the duct work inside the house ... I've put up thermometers at the air intake and at one of the vents right under the HVAC unit so I can monitor things inside the house. the tech took all their temperatures at the unit up on the roof.

    Model M Man - Good idea ... I'll see if I can get them to do that ... be just my luck that it will take an hour and a half next time to shut down.

    Many thanks for the suggestions ... might even have a chance with my next service call !
    What was the timeframe????

    If you are still experiencing the SAME problem as before.....to me that means that they still have yet to properly diagnose your problem and fix it. So therefore, you should not be charged for additional diagnostic fees. The parts, maybe, but they have yet to complete your system diagnositc.......cause if they did, you wouldn't be here right now.


    If I were you, first thing Monday morning I would in their office with their manager raising hell. Cause you've blown probably close to a grand now and still have yet to have a properly functioning system. Thats just bullsh!t there. And I wouldn't stand for it. So neither should you.


    As far as the SH/SC, you should review your copies of the invoices. I ALWAYS wrote down my pressures/temps/SH/SC/OD/ID......EVERYTHING!!! Cause thats the only way a history can be built. Not to mention, in a case like yours, I would want to see the previous readings at every call. That would give me a head start and would help to find the problem.


    Good luck, and continue to ask questions. We cannot diagnose your problem since we are not there. We can't really get too technical either with it being an open forum. And I can't tell you what to do but I bet there is a tech on this site somewhere who is from your general area. And this is by far the best place to find a good tech.
    I fully support the military and the War on Terrorism.


    If you don't know, then don't do. If you don't know and still do, then be prepared to pay someone else a lot to undo what you did and then do it right.

    If you do know, then do. But do it right. Otherwise, you may not be doing it long.

  8. #8
    Join Date
    Mar 2005
    Location
    Suppy NC
    Posts
    4,513
    Quote Originally Posted by Sacniteowl View Post
    Hi,
    I am a home owner with a 16 yr old Lennox 5 ton rooftop combo heater/AC model GCS16R-651-75-3P. I am dealing with a loss of cooling after about 45 minutes of running. Three separate visits by professional A/C service have resulted in doing the following:

    1) replaced contactor for compressor and one discolored terminal
    2) replaced compressor capacitor
    3) replaced evap fan motor and cap

    After each visit, the unit was running well with a 20+ degree difference in return air and exit air in the house. After 35 to 50 minutes, the cool air stopped although the evap fan and the house blower continued to run .

    Each time the service men came out they checked freon pressures, amp draw on the compressor, resistance on the compressor motor leads etc. and said all was OK.

    The service men do not seem to have any strong leads on what to test next and its getting a bit expensive.

    Does anyone have any suggestions for further testing?
    Does any one know what temperature I might find on the external shell of the compressor that would cause the thermal switches in the compressor to trip? I would like to know if it is getting hot enough to trip or if it is below where one would expect the thermal protection to kick in.

    Appreciate any help or ideas ...
    i dont quite follow the evap fan. You have two motors condenser fan motor and blower motor. The blower motor blows the air into your house and through the eveporator coil. The condenser fan motor pulls the air through the conderser out side and is on top of the unit.

    now is this unit on the ground or on your roof? Did they clean the coils? A didrty condenser can cause a lot of problems

  9. #9
    Join Date
    Jun 2005
    Location
    SW Wisconsin
    Posts
    4,871
    A real easy diagnosis using Superheat & Subcooling.
    When the superheat is way too high the compressor will overheat & go off on the thermal overload.

    Why in the world were they changing out parts?

    http://www.udarrell.com/ac-trouble-s...ubcooling.html

  10. #10
    Join Date
    Jun 2007
    Location
    Round Rock
    Posts
    3,517
    I really think you are wasting your money trying to fix this thing. After you get the problem fixed, one of the coils will start leaking or your compressor will die. I would consider replacing it and see if you can work some sort of deal with the company trying to fix it for a discount for so many service calls. You're really playing with fire wasting your time trying to fix this thing.

  11. #11
    Join Date
    Mar 2005
    Location
    Suppy NC
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    4,513
    Quote Originally Posted by bmathews View Post
    I really think you are wasting your money trying to fix this thing. After you get the problem fixed, one of the coils will start leaking or your compressor will die. I would consider replacing it and see if you can work some sort of deal with the company trying to fix it for a discount for so many service calls. You're really playing with fire wasting your time trying to fix this thing.

    why is this always the answer? Yes sometimes it is better to replace then to try to repair but not always. Seems the days of fixing things are giving way to the salesman.

    Dont know how to fix it then just replace the dam thing WTF

  12. #12
    Join Date
    Jun 2007
    Location
    Round Rock
    Posts
    3,517
    Quote Originally Posted by tinknocker service tech View Post
    why is this always the answer? Yes sometimes it is better to replace then to try to repair but not always. Seems the days of fixing things are giving way to the salesman.

    Dont know how to fix it then just replace the dam thing WTF
    I agree that things that can be fixed that offer some reasonable expectation of reliability, should be fixed. It also appears that you have some degree of experience in the field. Which probably leads you to have a rough idea of what a repair of this system would cost regardless of geographic region and what the realistic expectations of reliability and possible problems that can develop on a system of this age. How can you in good conscious recommend fixing this? I would fix it if the customer requests, but I would also tell them the not always liked but very distinct possibility of what will likely happen. Fixing things for the purpose of fixing things is very noble, but only in the best benefit of the ego of the person involved in fixing it and not necessarily in the best interests of the customers pocketbook. If it was 5 years old, fixing it is better, but at 15, a complete waste of time.

  13. #13
    Join Date
    Feb 2008
    Location
    Western NC
    Posts
    2,504
    I fixed a 35+ yr old walk-in cooler last week. Age is nothing anymore. Its all about the condition of the equipment.

    Not to mention that if the problem was found up front, all these un-needed parts would not have been installed.

    He has had 3 part-changers out. Once the real techniciain shows up, then his problems will be identified. But just throwing on parts and hoping for the best is not the way to go. And neither is giving up right outta the gate and trying to sell a new system. You gotta diagnose the problem before you can come up with a solution.
    I fully support the military and the War on Terrorism.


    If you don't know, then don't do. If you don't know and still do, then be prepared to pay someone else a lot to undo what you did and then do it right.

    If you do know, then do. But do it right. Otherwise, you may not be doing it long.

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