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central ac unit fans run in reverse?

18 years ago

Hi, I was wondering if someone could help me out. My American Standard ac unit started making a screeching noise. The repairman came and oiled the motor and runs smoother now but the fans we noticed are running in the opposite direction (arrows point the other way on the fans). Anybody might know what could be causing this or if there is a switch to make it go the other way?

Thanks!

Comments (21)

  • 18 years ago

    if the fans run in reverse, then it would be sucking where it should be blowing. either he changed the fan with the wrong one or he installed it backwards. either way, he needs to come back and fix that for free, unless you are just mistaken about direction of flow.

    is everything working, is it cooling the house properly and blowing cold out the vents and sucking air in teh returns? on the outdoor unit is it blowing the air up out the top?

  • 18 years ago

    Normally condenser sucks air from the side and blow it out top so you might have it reversed before he oiled it if he didin't take off the wiring and rewire. A lot of motors has wiring that you just switch to make it run the other way. Hope this helps.

  • 18 years ago

    Very helpful thanks - so you think it might just be the wiring needing switched? The house still runs cold yet the repair guy said he hadnt seen anything like that before and was telling me he was going to bring another motor over to fix it monday, how much might that run me?

    I do appreciate all the help, I am learning a lot the further I dig into this!

  • 18 years ago

    Yes if it's an univeral replacement motor not an OEM one then most of the time just switch the rotation wire will do. Motor costs varies but the universal ones we sell are all under $100 but technican need to drive and pick it up for you and what not so let them earn a little too. Hope this helps...admin@gsistore.com

  • 18 years ago

    Ask him to check the wiring and test the run cap before replacing the motor (capacitor).

  • 18 years ago

    Without seeing the unit, I do know for a fact that older Trane units (american standard is from same plant) with the capacitor wires reversed, will make the motor run backwards. If he pulled the top to oil the motor and it was running fine before, I'd lay money on that.

  • 18 years ago

    My money is on the run capacitor for the fan motor. I have seen hundreds of motors that run backwards when the run cap pops or shorts out. I would have him just put a new run capacitor on, while your watching, and turn it on. Chances are it will run in the correct direction.

    IMO
    Hope this helps

  • 18 years ago

    Running backwards is what caused the strain on most likely the sleeve bearings to fail. Even if the motor is reversible and be corrected from a prior idiot installer, the bearings are sure to whine again soon.

  • 15 years ago

    Runs in reverse. turn breaker for 5 minutes turn back on fan runs in correct direction then when it cuts off and back on its running in reverse. Tech just put new compasator in

  • 15 years ago

    Runs in reverse. turn breaker for 5 minutes turn back on fan runs in correct direction then when it cuts off and back on its running in reverse. Tech just put new compasator in

  • 15 years ago

    I'm having the exact same problem. Do you have it figured out?

  • 14 years ago

    Outside Air Conditioner Unit: Fan Spinning in Reverse

    Recently I replaced the contact relay and the capacitor (dual capacitor) on my 2.5 ton Payne outside unit. I thought that I wired everything on to the new capacitor correctly by following the wiring on the old capacitor. However, when turning on the unit, the fan on the outside unit spun counterclockwise. The unit was Sucking In Air rather than blowing it out, which is bad for the unit.

    Solution: Originally on my unit the Brown Fan wire went to the Fan position on the old capacitor. The other Light Colored Yellow Fan wire went to the Common position on the old capacitor. However, wiring it the same way on the new capacitor reversed the rotation of the fan, thereby causing the unit to Suck In Air. By reversing the Fan Wires on the new capacitor, the fan spun clockwise and the air was blowing out of the unit. On the new capacitor the Light Colored Yellow Fan wire was this time connected to the Fan position of the new capacitor and the Brown Fan wire was connected to the Common position of the new capacitor.

    Note: If your compressor has a delay in starting, you may want to consider adding a hard start capacitor. This has two Black wires that are wired to the Compressor position of the capacitor and the Common position of the capacitor. Wiring order does not matter.

    Crabman

  • 11 years ago

    My son changed fan motor out on mine & it was turning in opposite direction so he bent blades on fan so it would blow air right direction. It is out of balance & fibrates & screws keep coming out. So I need to buy new fan that is balanced what do we need to do to make fan turn correct way?

  • 11 years ago

    You son is a hack - don't let him fix anything else.

    Motors have a direction CW or CCW. Additionally you can get fan blades for CW blow/suction or CCW blow/suction.

    Some motors are reversible.

    Since you already have the motor, you son will have to purchase a new fan blade with the correct blow/suction.

  • 10 years ago

    i am sorry but that is so funny, i am laughing to death

  • 10 years ago

    Some fan motors are CW or CCW rotation only.. They will not "blow" now matter what.. the up side is the compressor still going to cool, even if it "sucks"... maybe with some slight theoretical thermal loss of efficiently but electrically speaking the system doesn't care.. I ran one fan backwards for years and other than a few leaves stuck on the bottom of the compressor floor it suffered no ill effects... whatever you do DON'T go bending fan blades..

  • 10 years ago
    last modified: 10 years ago

    I have replaced two evaporator fans for family members who could not afford a repairman. One of the units was designed to suck air in the other to blow it out. You can save big bucks by using the knock off motors. I bought one for kid u not $35. The last one was $75 :-( but the original TRANE motor retailed for ever two hundred. I had to cut the shaft to make it fit and figure out that the original dual capacitor could still be utilized to start the compressor even though the knock off motor required its own run capacitor but everything is clearly labeled so it doesn't take a rocket scientist to figure it out. The knock off motors have reversing wires such that when you switch them the direction of the fan motor reverses. Sometimes I switch them just for the heck of it. It's kind of fun. No difference in cooling or efficiency as far as I can tell. Sometimes I trick my wife and ask her if that fan is sucking or blowing. After she answers I go out and switch the wires to prove her wrong. :-). This sounds hard but it's really easy. Unless you want to leave this earth literally and figuratively make sure the 220 breaker is OFF. Some electricians put the 220 in the main breaker box but only label the low voltage control circuits. They figure this way there will be fewer guys messing with their own AC compressors because those guys will be dead. If you haven't switched off a dual circuit breaker with at least 40 amps you've still got 220 volts in the circuit! Regardless of the fakey 20 amp breaker labeled AIRCONDITIONING SYSTEM. when all else fails check the voltage going into the contactor switch with a volt meter. If you don't know how to do that call a repairman and while you write that check for $500 smile while telling yourself IM STILL ALIVE :-)

  • 10 years ago

    And by the way.....I love that guy that bent the fan blades. He thinks way outside of the box. Isn't there a song by the beach boys about GOOD VIBRATION

    :-)

  • 8 years ago
    last modified: 8 years ago

    I have a similar problem except mine sometimes runs correctly sometimes in reverse. I replaced Fan motor, Blade and capacitors 4 mos ago and all fine until now. I checked the values on the capacitors and they check out ok. Once it was running forward and I squirted water on the coils and when some water got on the fan blade it reversed right before my eyes. I'm stumped. I'm thinking about calling a priest instead of an A/C tech. In the mean time I have water misting on the coils so I can have A/C in this 109 Texas heat. I hate to just change out parts until it gets corrected. I want to correctly diagnose it.

  • 8 years ago

    The only explanation I can think of is the water is wetting a capacitor connector and changing the capacitance value enough that AC current changes and causing the motor to reverse.

    Start a new posting if you want to continue the trouble shooting discussion.