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AC technician replaced my condenser fan (through a home warranty service). The new fan worked for 5 min and stopped working after that. the fan motor was extremely hot (180F or more) The old fan motor was 1.4 A 240 V and 1/4 hp. the new motor is also of the same configuration. the only thing i missed out is the RPM. i don't remember the RPM of the old motor and the new motor RPM is 1040. The AC technician took away the old motor and recycled it.

What can be the problem here?

I looked in some forums that the RPM mismatch can overheat the motor and damage it. i have no way of knowing the RPM of the original motor. I looked in manufacturer manual and there is no mention of it. is RPM matching that important?

http://www.nordyne.com/Literature/423a.pdf [ My unit is maytag DS3BD-036K ]

Very similar to question What could cause a replacement A/C condenser fan motor to only run for 3 minutes?

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  • Did the tech do any other work to the system, like trying to figure out why the original motor died? If the problem that killed the old motor was not corrected, it's likely that the new motor was killed by the same thing.
    – Tester101
    Sep 11, 2014 at 0:57
  • He didn't did any other testing. I think the guys these house warranty companies hire are really lousy. what are the possible causes of such a problem? what can be those tests?
    – David
    Sep 11, 2014 at 1:05
  • Faulty replacement out of the box? Was it spinning the correct way when they were done? What other problem could it be than a chattering contractor, which it really shouldn't mind?
    – Mazura
    Sep 11, 2014 at 2:50
  • @Mazura, Maybe the motor was faulty but it did ran for 5 min. So i believe there is some incompatibility in the new motor rather than its just faulty. Does RPM can constitute to this problem
    – David
    Sep 11, 2014 at 4:59
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    @David It doesn't matter if the system is out of warranty. If a) the tech used the wrong part, and b) it failed because he used the wrong part, and c) he reasonably should have known that the wrong part would cause failure, then the tech should be responsible for replacing the part.
    – longneck
    Sep 11, 2014 at 13:14

2 Answers 2

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Does RPM effect motor life? More than I thought it would.

"if you change an 825 motor and put in a 1075, your HP load will move from 1/6th to 1/2... with the same blade. and the noise level will go up dramatically in the unit."-vstech, HVAC Talk

"Plus you're probably going to eat a few motors in the process."-Six

Five minutes sounds about right when you ask a 1/4hp motor to give you 1/2hp.

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  • What requires the HP and the RPM load to have to be exact? Is it the blades? The capacitor? If just looking purely from a electrical standpoint, changing to the correct cap is the only thing I can think of unless the control board is also part of the equation.
    – LeanMan
    Dec 10, 2021 at 23:24
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The tech wired the motor incorrectly. May have overpowered causing high heat; tripped thermal overload.
Seen this many times.

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