Question for home HVAC guys or electricians

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d55dave

d55dave

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So I am in the process of trying to sell one of my rental homes, to simplify life a little. Unfortunately, the 25+ year old central air, which has always been trouble free, will not come on this year and I need it fixed for the sale deal to go through.....

When it is turned on the furnace fan comes on and the compressor runs but the condensor fan does not run. I have checked the big capacitor (fan starter?) in the unit and it checks out good. I suspect that the fan motor is no good. It only has two wires going into it and there is no continuity over them. I have a universal motor, same shaft size, same rotation but slightly more HP and rpm. The new motor can be wired for 120 or 230 volts (old one was 230), but the new motor has two extra wires for a capacitor (starter).

What kind of capacitor do I need for the new motor, can I wire it up without it? Is the large capacitor in the ac unit for the fan motor or the compressor?

Thanks in advance for any help or ideas.
 
Well IF this motor you have that is "universal" is designed for an outdoor condensing unit it has to have a label showing wiring and condenser (capacitor) hookup

so this new motor should be

weatherproof

have ball bearings and not bushings

be at least as much HP as the old

AND BE THE CORRECT RPM. Because more RPM is going to pull more power trying to turn the fan, and less RPM of course won't move the same air.

It should have a label showing wiring hookup, and SHOULD show the run capacitor value. If not you should be able to tag it down by part no.

None of these motors ever use a start cap. They all use a run cap.

"Extra wires" Sometimes universal motors are reversable, and sometimes motors have dedicated capacitor wires, usually brown. Some motors only have one cap wire, and the remaining cap terminal is common with one of the other wires.

BE CAREFUL.

Most "better" AC units have a start AND run cap for the compressor. SOME RUN caps are "dual" IE usually 3 terminal, with one terminal common. There will be one section cap for compressor run, and a second section for the condenser motor.

THERE IS NO REASON to assume that the old condenser fan cap will be the same value as the new one. "We used to" replace any cap along with a new motor. You REALLY don't want to find out the reason the motor failed is because the cap failed!!!!

START caps are normally ONLY used on compressors, and almost ALWAYS black plastic rather than a metal can

I would certainly make an effort to troubleshoot and make certain the motor is actually bad. If it doesn't smell burned or turn hard, it might be OK.
 
Mine is a 26 year old Trane. That outside fan motor has been replaced once. It made a heck of a noise so I knew it was going to fail. Being a rental property you may not of heard or noticed evidence of impending failure. It didn't break the bank to buy the correct fit replacement.
 
Thanks for the info guys. I live next door....my bedroom window faces the ac unit so I would have heard it. If anyone wants to learn from my mistakes I could write a book on rental properties, LOL. I have a friend who owns a local electrical contracting company, he is going to put me in touch with one of his suppliers and get me the right motor. He agreed that I should not mess around with improper replacements.

I am so looking forward to selling the rentals off and having some free time and extra cash to play with cars again!
 
OK so after you get out of rental properties and into cars again... wanna buy a 67 B'cuda vert project ?
 
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