I have a 3 ton air conditioner. Recently the condenser fan motor quit, it was a two speed motor. The local HVAC company replaced the motor with a single speed unit. They insist that the two speed motor is not necessary, no one uses them any more, and that the single speed motor in more than adequate. Are they giving me the right answer, or were they just selling the motor that they had in stock and did not want to be bothered with fixing it to the original specification?

As long as the unit is single stage , you will only need one speed, maybe earlier on someone replaced that motor with a 2 speed, a lot of universal motors have more than one speed, give us a little more info on your system.

Some of the old units had a 2 speed fan, they where sold as a super high efficiency, but the difference of High and low speed amperages, in actuality, saved very, very little. If not a 2 stage A/C, the low speed is not necessary. Only real benefit for the low speed is to keep the head pressure up if the outside ambient temperature is quite cool, to which I say, open a window. :cool:

I have answered this twice, but it did not take since I was not registered yet... ugh...

Anyway, I will try for a third time, since I am currently working on a friends unit and it is a 2 speed, which is expensive to replace with an OEM replacement motor.

First of all, I would like to acknowledge NorthernHeat as having the best answer, but I would like to take it a step further.

Most contractors will keep a few universal motors on their truck, and most will simply replace the motor without asking you first if you would like to wait for them to order a 2 speed fan motor and what's worse is they will probably just grab the universal motor, which is usually rated at 1/4-1/2hp and simply replace it, and give you your bill for about 300.00

Not only have you been hit hard by the price of the going rate of an HVAC contractor, they have essentially roasted you for years to come with the monster motor they stuck on your condenser!

Most high effiency condensers that would come with a 2 speed fan motor, will have a very efficient fan motor also. For example, I am working on a Trane 2 speed, 2400 or 2 ton condenser, which has a fan motor rated at .5 amps and 1/20th hp, 825 rpm. Now your condenser has a fan on it that is designed for your unit, but for all intents and purposes, you can always pull a Tim the Toolman, and over power it with the universal 1/4 or bigger hp motor, and you will probably never even notice the difference on your power bill due to the fluctuations in the power bills.

Trust me though, you will be paying through the nose if you do not check out what size motor gets put on your unit. If it is a Trane Dealer, you may get the OEM motor, but you may not, and most contractors do not take the time to explain the difference and order the correct fan motor for you. If they do, you can expect to pay over 200.00, just for the motor. This may also be true if you have a Carrier and use a Carrier contractor, as the brand makes no difference in this example. It's just a better chance that the dealer that carries the brand you have, will have access to that fan motor, and another may not.

This is why I agree with NorthernHeat that replacing the fan with a single speed model would be the right thing to do, as you will save little if anything with the 2 speed motor, and the replacement cost will never be returned. The 2 speed motor rarely runs in the low speed stage, except in rare cases of removing heat while there is cold ambient air temps, like removing heat from a commercial kitchen in the cooler seasons. Even then, the slower speed stage, will not save you much if any money on current draw at the lower speed, so replacing the fan with a high efficiency single speed motor will be perfectly OK.

I have been checking the prices of the motors to replace the one on my friend's 2 ton unit, and the going price is about 175.00 for a direct replacement motor, whereas, a single speed version is closer to 75.00. I just happen to have a used one that I would give my friend, but he is really picky and will probably buy a new one as he has money coming out the Wazoo.

Let me state that not all contractors will just automatically grab the universal motor, and it is usually the guy that does it on the side and don't know the difference that is more likely to do this to you, but it is still up to you to make sure you got the right motor, as most people will not know the difference and will be paying dearly for the convienience of just grabbing the universal motor off the shelf in his truck, rather than taking the time to do it right.

If you ever come across this situation, and have to wait for a fan motor to be ordered, I have gotten by with taping a 15.00 box fan on top of the condenser, and leaving it on high until the correct motor comes in. This will work in a lot of circumstances, but it may not work on some of the bigger units. Removing the old fan will help, and a good cleaning of the coil will always help, but it is worth the chance to try it and see if it will keep your compressor from drawing too many amps, till you get the right motor in. If the compressor likes it, then run it and stay cool until you get the right motor.

Sorry for the long post, but they don't call me "Motormouth" for nothing...

Dan Lemke
Bluford, IL

Sorry Dan,that post is a couple years old,most likely the OP won't ever read it.

Ahh yes hvacservicetech_007, but there are many others that stumble onto this post later and absorb the good info given by all you guys ;-). Yep, there is also plenty of air flow with the furnace fan motor, duct outlets all open and unobstructed, clean filter, clean condenser coil etc, just in case those thoughts come up for others.

I need the 2-speed since the wife needs air conditioning when its 70 degrees out or less and I don't like the frozen evap coil LOL (or the chance of the compressor dealing with this). Reasons are leftover heat in the house from a hot day keeping the AC running late into a cool night, too much humidity at night to warrant the value of that air (I won't go techy for the sake of others on heat value or whatever it was, been a while), women with power surges such as menopause, life's usual such that are actually enough reasons that a 2-speed can still offer simple help to work well for some like this (without adding other controls like low-pressure cutout, timed restart etc). And for the sake of discussion, a separate window shaker for the bedroom is a good idea too, long as it don't frost its evap coil too.

Just one update, with respect, on the use of a house fan laid on top of the outside unit when the condenser fan motor dies, great idea and have used it, but they are not waterproof so watch out for that.

My house's AC does not have a 2-speed condenser fan, yet, I am actually checking into adding it to the Carrier unit we have since its still only a few years old/good unit/good SEER.

Thanks for all your info guys, and letting me add some, but for sure correct anything I goofed on.

Jeff M
Eden Prairie, MN

Put a low ambiant control on the outside unit and the evaporator ice condition goes away. I use variable speed units so the condenser motor speed is matched to the condenser discharge temperature at the liquid line. Very smooth setup.