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  1. #1
    Join Date
    Sep 2006
    Location
    Winter Springs, Fl
    Posts
    1,755

    38yxa fan cycling in heat mode

    I was doing a final charge check on a carrier 38yxa036320 date code 4402, fv4anf003 date code 4402 with a thermidistat today and I noticed something odd.
    the OD fan was cycling momentarily only during heat mode. it didn't seem to be going into defrost since ODT was between 50 and 55 f and space temp was in low 60's during this ( no ice on coil but there was light ice accumilation at the defrost klixon during the loss of fan ) . I couldn't successfuly check the charge in heating so I switched over to cooling quickly and everything seemed ok. fan stayed running the whole time in cooling. switched it back over to heat and the same thing again. during lunch I went to totaline and got a new def. board thinking it was a bad relay or something, no luck. OD fan motor was stone cold so the motor wasn't tripping out on thermal. wire wiggle test didn't help either. tried it with and without quietshift ( at that point I was guessing/ trying almost anything ) I didn't have a lot of time to fully diagnose this out since I was there to do a trimout and a final performance check was supposed to be a small portion of my work there. this was a remodel job in which we relocated the equipment and reducted 95% of this system. I have no prior performance history on this system since the HO's just bought this house and had it gutted/ added on to. I know this is going to come up later so I want to have an idea of what to look for. anyone out there had this happen before? does this unit have some sort of motormaster control built into the defr. board? I have never seen a heatpump do this.
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  2. #2
    Join Date
    Jun 2001
    Location
    Louisville, KY
    Posts
    12,145
    Vapor pressure switch.

    Will you ever register as a pro? I could give you a complete explanation if you could post in the professional section.
    Perhaps you should have read the instructions before calling.

  3. #3
    Join Date
    Sep 2006
    Location
    Winter Springs, Fl
    Posts
    1,755
    Quote Originally Posted by jrbenny View Post
    Vapor pressure switch.

    Will you ever register as a pro? I could give you a complete explanation if you could post in the professional section.
    yeah I guess I could. ST asked me about that once recently. I had never thought about it until he said something about it.

    so is it bad or are you going to make me wait until I reg as pro? email me direct if you can't post here. kev-1 at earthlink dot net.
    If you can't learn to do something well, learn to enjoy doing it poorly.

    The HVAC-Talk Educational Forums is the best place on the net for your HVAC/R info!!!

    VETO PRO PAC - The Official Tool Bag of HVAC-Talk.com

  4. #4
    Join Date
    Jul 2006
    Location
    Chattanooga, TN
    Posts
    20

    vapor pressure switch

    410A and pressure vessel codes....these pressure max out ...and some state codes do not allow for 410a head pressure INSIDE THE HOUSE! without limiting pressures? Im not sure if this is the answer... Carrier stopped using the pressure guard kit on their PWM GE Motors.

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