Five Wood

AC Fan Stops Momentarily

19 posts in this topic

I have Colman Mac 15K AC unit that is 2 1/2 years old.  In the last couple of days the fan will pause momentarily and then start again, while it is already running.  It doesn't do it on start up, so I don't think it's the start capacitor.  When this happens a burnt smell comes through the vents.  It would seem that the fan motor is binding up.  Any idea's on a fix for this?  Or is the fan motor on it's way out?

Thanks

Jim

   

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First the fan motor doesn't have a start capacitor just run a capacitor, you will have to go up on thr roof and take the cover off and make sure the motor spins freely without any power to it. If it binds at all it will need to be replaced.

 

Denny

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FWIW (zero) I'm with D&J on this one. Unlike the higher starting torque of a compressor, the low torque fan doesn't require any start capacitor, so Id go up top and clean and blow out any dust in/on the fan blower motor and see how well it freely rotates ?? and light lube if its so equipped to do so.

John T  NOT by any means or stretch HVAC experienced so go with their advice over mine.

 

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4 hours ago, D&J said:

First the fan motor doesn't have a start capacitor just run a capacitor, you will have to go up on thr roof and take the cover off and make sure the motor spins freely without any power to it. If it binds at all it will need to be replaced.

 

Denny

Denny

I have checked the motor and it spins freely.  If the "run capacitor" is bad, will that allow the fan to stop?

Jim

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Sometimes thing will run until they build up a certain heat or amps then cut out and come back on when the "cool down" 

A good example is a temprature sensor on many if not most small compressors. It goes by the name of Klixon a lot although if I recall that is a brand name that get used for the same type product. It is used to protect more expensive parts like the compressor.  My daughter and son in law had one save their compressor on the fridge. He called me  and I could actually hear it on  click off ant then click again when it cooled down and reset over my cell phone.  He ended up adding a hard start kit and so far so good.   I doubt your fan motor has one but the fan itself or the switch or something else could be doing the same thing.  The high speed on my Chev. fan did this for a while but eventually it quit.  The motor was still good and still operates on the four lower speeds so mine is in the speed control.

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On my Dometic Brisk Air II the fan will briefly (one second or so) shut off to change speeds.  For example, if the heat is such outside that the a/c is getting behind, the fan will switch to high speed.  Then, after it catches back up, it will shut off briefly and switch back to a lower speed.  I don't know if that could be what you are referring to.  It definitely doesn't have any smell when it does it though.

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2 hours ago, Five Wood said:

Denny

I have checked the motor and it spins freely.  If the "run capacitor" is bad, will that allow the fan to stop?

Jim

Yes if the run cap is going bad if could cause that kind of problem, check and see if it's swollen, that will happen on a hot day.

Denny

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1 hour ago, bigjim said:

Sometimes thing will run until they build up a certain heat or amps then cut out and come back on when the "cool down" 

A good example is a temprature sensor on many if not most small compressors. It goes by the name of Klixon a lot although if I recall that is a brand name that get used for the same type product. It is used to protect more expensive parts like the compressor.  My daughter and son in law had one save their compressor on the fridge. He called me  and I could actually hear it on  click off ant then click again when it cooled down and reset over my cell phone.  He ended up adding a hard start kit and so far so good.   I doubt your fan motor has one but the fan itself or the switch or something else could be doing the same thing.  The high speed on my Chev. fan did this for a while but eventually it quit.  The motor was still good and still operates on the four lower speeds so mine is in the speed control.

The fan motor only has a thermo overlaod built into the windings, it opens it will not come back on until the motor cools down. The compressor has a current overload (klixon) that will open if the compressor gets short cycled, it also has a thermo overload in the windings that will stay off for a couple of hours until it cools.

Denny

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2 hours ago, D&J said:

Yes if the run cap is going bad if could cause that kind of problem, check and see if it's swollen, that will happen on a hot day.

Denny

The top of the capacitor has not pushed up.  But they are certainly cheap enough that I will try changing that out to see if it corrects it.  It's strange though. . . there are two capacitors in there and neither one has any markings on them what so ever to assist in ordering a replacement.  The schematic shows which one is for the fan.  I will have to call Coleman to get the proper number.  

Thanks for the help

Jim

 

Edited by Five Wood

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11 hours ago, Five Wood said:

The schematic shows which one is for the fan.  I will have to call Coleman to get the proper number.  

Because they are cheap, I'd probably do the same but the reality is that even the most technically competent of technicians can only guess if they are not there to take some readings and run some tests. In a prior post one of the members who has a/c repair background mentioned that most of us don't have much knowledge of a/c systems and as a retired service tech myself, I would agree with him. Air conditioning systems are a bit on the unique side of things and tend to be rather specialized. Unfortunately, few RV certified techs actually know a/c well either so many an RV air conditioner gets replaced when a relatively minor repair would have solved the problem if the service tech had known more. 

 

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Good evening Jim, FYI I can take my old antique Simpson 260 ANALOG VOM and test good enough to see if a capacitor is totally bad and can gain some insight into if its charging characteristics, HOWEVER, it takes a real and true capacitor tester to properly test a capacitor. That being said bulges and swelling can be indicative of problems, but often I have seen good capacitors with loose burned corroded connectors that were the problem instead. If it were me and the connections all looked good with no evidence of heat or carbon (and you say it turns freely), for no more then the cost if you can get to things and do it yourself, I might just buy BOTH new replacement capacitors and install them while you're in there. Based on what you said if the capacitors cure the problem its fairly cheap n simple, but even if not, you're not out all that much, nuttin ventured nutting gained right??

BUT I don't like the sound of that burned smell you spoke about !!! If things were damaged a capacitor may get her going for a while but it may not last long depending on prior damage.

 AGAIN I'm NOT an AC tech or service person and just have an electrical background, so do as the HVAC experienced gents say instead of little old me lol

John T

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remind me how to discarge a capacitor please

safely would be nice

Edited by bigjim

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Short across the terminals with a screwdriver. 

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2 hours ago, bigjim said:

remind me how to discarge a capacitor please

safely would be nice

I prefer a jumper wire and series resistor across the leads to discharge a capacitor ESPECIALLY IF A BIG ONE. I don't like a sudden low ohm near dead short (like a screwdriver) as there's an arc n spark and heat and potential short term high current (Subject to capacitor size and voltage and stored energy), and besides that it scares me and makes me jump lol

However it indeed 'works" lol and I've seen it done many times, but I prefer a lower current slower energy discharge myself.

But to each their own method, anyway anyone chooses to do it is fine with me..........Just because I don't like it one way don't mean others may not ............... 

 John T  NOT an HVAC expert, do as they say if you like, but I do have an electrical background

 

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11 minutes ago, oldjohnt said:

I prefer a jumper wire and series resistor across the leads to discharge a capacitor ESPECIALLY IF A BIG ONE.

While I have seen it done many times with a screwdriver or a handy piece of wire, there are many effective ways to do most things, but this method is safer and smarter. As a field tech, I carried a jumper of this type for the purpose.  I made the discharge device that I carry today using a 15Kῼ,  5-watt resistor but the instructions from this link are pretty much what I did. 

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12 hours ago, Kirk Wood said:

While I have seen it done many times with a screwdriver or a handy piece of wire, there are many effective ways to do most things, but this method is safer and smarter. As a field tech, I carried a jumper of this type for the purpose.  I made the discharge device that I carry today using a 15Kῼ,  5-watt resistor but the instructions from this link are pretty much what I did. 

Thank you for that link Mr K as I found it very informative.  Went into my save file(s) for future use.  :)

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I didn't take the time to construct a pretty one like shown in the URL Kirk was kind enough to post lol. Mine were usually a jumper wire with the resistor leads spliced in and a probe or alligator clamp etc to attach to the capacitor terminals. But I still didn't have to encounter a big scary spark and a loud POP even though sure it took  a tad longer and a bit more effort to discharge a huge honkin scary fully charged capacitor !!!!!!!!!!!!!!!!!!!!!  I HATED SPARKS N POPS AND STILL DO TO THIS DAY............

 

 John T

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1 hour ago, oldjohnt said:

I didn't take the time to construct a pretty one

I suspect that I used one much more in my line of work than you did in yours. Like most service techs, I don't care much for the sound of arcing either. It gets too close to the sound of an arc welder, and sometimes even does some welding!:wacko:

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