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  1. #27
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
    Posts
    14,914
    Quote Originally Posted by TamarHV View Post
    Do you guys check MFDS on capacitor every time you go on tune-ups? Be honest and catholics dont answer. joke
    I check the compressor, condenser fan, and blower motor run capacitors 100% of the time, and strongly recommend replacement if it is more than 10% off the rating.
    I also write the capacitor size inside the control compartment with a Sharpie.

    Once you start testing every capacitor, you will be shocked at how many weak ones you find.

    I try to only use AmRad made in USA capacitors, but the Mars brand made in Mexico capacitors seem to hold up very well. The Mars2 brand, and pretty much every other brand, are garbage.
    If more government is the answer, then it's a really stupid question.

  2. #28
    Join Date
    May 2012
    Location
    Des Moines, IA
    Posts
    56
    ill test them if they look bad. most times ill give them the option to replace if they want to since its such a crap shoot if its old. we charge lower on a tune since we are there anyway and getting it then is better than having it fail and have to pay for a service call too. always write it on the ticket. ive had real bad ones and the customer would cheap out on it, have it fail 3 weeks later and not want to pay a service call

  3. #29
    Join Date
    Jul 2009
    Location
    South Carolina
    Posts
    3,100
    I almost never check the capacitor on a working unit but then I don't do PM's either. I don't care how good you are, you can't guarantee that system won't break down right after you leave the job. Maybe once or twice a year so I don't forget the formula I'll check the cap on a running system. How can it be a call back on something you didn't fix to begin with?
    I'm curious about you guys who check the capacitor on every call.
    Have you ever had one that checked good & went bad within a month after you left?
    Gary
    -----------
    http://www.oceanhvac.com
    An engineer designs what he would never work on.
    A technician works on what he would never design.

  4. #30
    Join Date
    May 2005
    Location
    South
    Posts
    580
    Quote Originally Posted by garyed View Post
    I'm curious about you guys who check the capacitor on every call.
    Have you ever had one that checked good & went bad within a month after you left?
    Yup, especially after a storm went through. And the customer is always pissed off expecting us to have predicted it when we were there the last time.

  5. #31
    Join Date
    Feb 2012
    Posts
    59
    I've seen caps running at half their mf rating and still "working." I wouldn't want to leave that call without informing the homeowner and documenting the situation.

  6. #32
    Join Date
    Jul 2009
    Location
    South Carolina
    Posts
    3,100
    Quote Originally Posted by truck12 View Post
    Yup, especially after a storm went through. And the customer is always pissed off expecting us to have predicted it when we were there the last time.
    I would think with the quality of caps made today, checking them as good one day is meaningless as far as predicting reliability. I wouldn't be surprised if a cap that checks low & is still doing enough to keep the system working lasts longer than one that checks perfectly fine.
    Gary
    -----------
    http://www.oceanhvac.com
    An engineer designs what he would never work on.
    A technician works on what he would never design.

  7. #33
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
    Posts
    14,914
    Quote Originally Posted by garyed View Post
    I wouldn't be surprised if a cap that checks low & is still doing enough to keep the system working lasts longer than one that checks perfectly fine.
    Possibly, but if you don't check them, you won't know if it is weak, and a weak run capacitor causes the motor to run inefficiently, resulting in a reduction in cooling capacity, or airflow if it is a fan motor capacitor.
    If the compressor has a start kit, the run capacitor could be completely dead, but the unit still be working.
    If more government is the answer, then it's a really stupid question.

  8. #34
    Join Date
    Dec 2004
    Location
    Milton,Wisconsin
    Posts
    226
    Quote Originally Posted by garyed View Post
    I almost never check the capacitor on a working unit but then I don't do PM's either. I don't care how good you are, you can't guarantee that system won't break down right after you leave the job. Maybe once or twice a year so I don't forget the formula I'll check the cap on a running system. How can it be a call back on something you didn't fix to begin with?
    I'm curious about you guys who check the capacitor on every call.
    Have you ever had one that checked good & went bad within a month after you left?
    Yes, But I still check them on every call. If I find one out of range by more than 10 percent we recommend replacing. A lot of times people say go ahead and change it. I've never changed a weak one and had it blow a month later.

  9. #35
    Join Date
    Jul 2009
    Location
    South Carolina
    Posts
    3,100
    Quote Originally Posted by mark beiser View Post
    Possibly, but if you don't check them, you won't know if it is weak, and a weak run capacitor causes the motor to run inefficiently, resulting in a reduction in cooling capacity, or airflow if it is a fan motor capacitor.
    If the compressor has a start kit, the run capacitor could be completely dead, but the unit still be working.
    True,
    I can't even count how many times I've seen a compressor running with a totally dead capacitor & no hard start either. The only reason I find it because the fan won't run & it's a dual cap. I've never been able to figure that out. You'll have a totally dead dual cap on both sides & yet one of the components (fan or compressor) will still be working fine.
    Gary
    -----------
    http://www.oceanhvac.com
    An engineer designs what he would never work on.
    A technician works on what he would never design.

  10. #36
    Join Date
    Jul 2005
    Posts
    5,385
    Quote Originally Posted by garyed View Post
    I would think with the quality of caps made today, checking them as good one day is meaningless as far as predicting reliability. I wouldn't be surprised if a cap that checks low & is still doing enough to keep the system working lasts longer than one that checks perfectly fine.
    A capacitor that checks ok is more reliable than one that doesn't. The one that reads low is telling you that its dielectric is already breaking down.

    FWIW I replaced 3 capacitors on a single call today, and two more on the next call. On the first call I found one open, one weak, and one incorrectly sized. (Two units). On the second call the compressor had been running with an open run cap until the start cap finally blew. That covers every scenario discussed in this thread and then some, and I found them all within a two hour period.

    It pays, literally, to look.
    Last edited by hvacrmedic; 06-21-2012 at 08:11 PM.

  11. #37
    Join Date
    Jul 2007
    Location
    Tulsa, OK
    Posts
    975
    You open the machine, you check cap with no load, then while running using start winding amps x 2650, divided by across cap voltage. every time or your fired. Pull comp wiring and meg-ohm for baseline reading for future reference plus do the cond fan motor to boot period. Plus about 30 other variables not listed. My maintenance calls are at minimum 1-1/2 hrs each system to 2-1/2 hrs. My call back % is 1 to 3% and so is our other techs.

  12. #38
    Join Date
    Dec 2011
    Location
    Asheville, N.C.
    Posts
    103

    I will now.

    Normally I don't check the cap when everything is running correctly but I realize now that it would be prudent and a preemptive strike to do so. As always, CYOA!

  13. #39
    Join Date
    Dec 2011
    Location
    somewhere between here and there
    Posts
    478
    alot of caps have the varience stamped on them...+-6%

    if not stamped...10 percent is good choice( wiki says +- 5%)..
    but i usually use 10% unless otherwise stated....

    and if it is close to spec...i still reccommend change....

    we offer full money back guaruntee if equip fails within 6 mos of tune up.....

    assuming they change everything i reccomend.....

    and for those old skool guys.....piss off.....

    if i am going to GUARANTEE no breakdowns.... i mean it....

    but the way i do it is totally legit....change most of these 10 yo parts...and i promise it will still work!

    i also believe only a fool puts a new cap...or contactors in a 10 yo unit....

    at ten yrs old the system is done and out of warranty....

    why put a new crate engine in a 15 yo car????? stoopid???? yes\\\\\\\\\\\\1111


    Please, Please Please......keep the Factory Smoke in the Wires!!!!!


    Is it Rum'Oclock yet???

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