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Heating man · 11-17-2013, 04:27 PM

That black capacitor you are talking about is a start capacitor these have to come out of the circuit after the motor starts usually by a relay. The metal case capacitors are run capacitors they are in the circuit all the time. Normally start capacitors are used to start the compressor not the fan motor. Probably that start capacitor was for the compressor. You probably have a dead spot in the windings of the motor and if it stops on that point it will not restart. Motor is probably bad and will need to be replaced. Sorry but I have never taken a fan motor out of one of these units so I don't know specifically how they come apart. RV rooftop A/C unit I think are like window A/C units. Which have a double shaft motor with a fan on one end and a squirrel cage blower on the other end. The fan is usually not hard to remove but getting to the squirrel cage may be harder to get to for removal. Sorry I don't have more specific info.

cubano222 · 11-19-2013, 08:56 AM

Yea, it looks like I'm going to have to remove the fan motor & replace it. Guess when I get up there, I'll have to figure out how to get it out. It has a Styrofoam box over the squirrel cage part so I'll have to see how to remove that without busting it up.

cubano222 · 11-26-2013, 10:44 AM

I don't get it. It's too cold here for the compressor to start but I turned the fan motor on several times last weekend, at least 10 times over 2 days, & it came on every time, moving lots of air & spinning freely. If my fan motor is bad, why does it come on so many times & then every once in a while, just hums, even with new capacitor?

aschuh53 · 11-26-2013, 11:06 AM

has a bad spot on the armitcher that is why

TQ60 · 11-26-2013, 11:56 AM

Fan motor is shaded pole, no brushes so no windings in armature.

If will run with push then starting issue.

Confirm correct cap, then ohm out windings.

Also confirm wiring via diagram, easy to get copies but exact model model.

Roosters 67 · 11-27-2013, 07:19 PM

Jerry,

The fan motors are not that hard to replace on most standard design roof units. last one I did required seperating the evaporator case(cold side, inside coil), removing the styrofoam insulation and removing every screw that held the condenser (hot side, or outside coil) shroud to the pan. Once I had the condenser loose from the pan, i had to move it slightly up and away from the fan. The copper lines will flex as needed, just avoid to much bending of the lines. Don't recall where I got the motor from but it was online and ran about $115 shipped. While I had it apart I went ahead and replaced the capacitors, after all they are cheap enough.

Get all the numbers and specs off of the existing motor and some google action should find a replacement.

Good Luck my friend,
Spence

94-Newmar · 11-28-2013, 04:27 AM

Quote:

Originally Posted by Heating man

That black capacitor you are talking about is a start capacitor these have to come out of the circuit after the motor starts usually by a relay. The metal case capacitors are run capacitors they are in the circuit all the time. Normally start capacitors are used to start the compressor not the fan motor. Probably that start capacitor was for the compressor. You probably have a dead spot in the windings of the motor and if it stops on that point it will not restart. Motor is probably bad and will need to be replaced.

Cubano, Heating Man has it correct. The round black capacitor is indeed the start capacitor for the compressor, not the fan. I don't know how they tested them, but checking them with a multimeter that will test capacitance (micro/pico/nano/farads) still isn't a real world test with high voltage, amperage and load. Replace them all. After replacing them should you find it still is inconsistent in starting the fan I suggest checking amperage draw and voltage drop upon start-up/cycling with a good meter. It is entirely possible that you are getting a large voltage drop up there. I'm not telling you to simply throw parts at it, but in order to properly check voltage drop/amp draw you'll need to make sure that the capacitors are indeed good.