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Vintage 1978 RHEEM AC compressor fan not spinning..blowing caps, other issues...

Vintage 1978 RHEEM AC compressor fan not spinning..blowing caps, other issues...


  #1  
Old 03-15-10, 07:35 PM
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Vintage 1978 RHEEM AC compressor fan not spinning..blowing caps, other issues...

Sorry if this issue has been covered before. I have tried to find a solution to my problem before posting... after all its a lot faster than waiting. I got close a few times but then the threads got off topic and ended. I really appriciate any help that is offered!

Here is my situation:

We purchased a home built in 1978. It has the same AC unit from when it was built. After 2 years the dreaded "blowing hot air" symptom started... I replaced the fan run capacitor and all was well for a year. Then after about a year (almost to the date) same thing. I replaced run capacitor. Then 6 months... replaced capacitor.... I had an AC guy come look at it and he changed the wiring a bit and said the motor "ohmed out" as in checked out good and put in a new dual cap. it worked fine for about 3-4 months...


The AC guy charged me $200 to put in a cap so I just went and got another one... excpet this time I bought a bigger one thinking the older motor need more help getting started.

it blew like new (like really.. as if it was back in its prime and i have never seen it blow like this) and worked great for about 2 months and i noticed the fan seemed to be spinning slower than usual one day.. then the next day slower... the next day the AC couldnt catch up and stayed on and the house got hotter and hotter...I was outside when the compressor came on. the fan was barely spinning (like 1 rev a second).

So I unplugged it at that point and have been putting it off (thank God it was cooling off).

What I am asking is:

Is my motor bad? (it can be turned by one finger with no effort. and yet caps keep getting killed.)

How much if possible to fix current motor?

Believe it or not RHEEM says they have the motor in stock. for about $220.
 
  #2  
Old 03-16-10, 04:20 AM
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Sorry to say, anything you do to try and keep a 32yr old system running is a waste of time and $ IMHO
 
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Old 03-16-10, 05:12 AM
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With motors there are 2 types of failures generally
Electrical and mechanical. Electrically checking resistance of windings. Mechanical which power off spin the motor observing for excessive drag or resistance. If it doesnt spin freely it needs replacing.
When replacing a motor that requires a capacitor, always get a new capacitor with the motor that matches its microfard requirements. It should say on the motor or the box. There is a reason they specify a specify rated capacitor.
When you say the cap had blown do you mean exploded?
If your motor passed the electrical and the mechanical test i would be looking into if the capacitor rating matched your new motor and was it wired correctly.
 
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Old 03-16-10, 06:41 AM
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Originally Posted by dun11
Sorry to say, anything you do to try and keep a 32yr old system running is a waste of time and $ IMHO
Well if replacing a $10 cap will fix it I don't agree. Also the position I am in is either replacing the motor for $200 or the entire system for (from what I am told could be as much as $5000) so again... in my position the small investment is much easier to swallow and is not a waist of money if it will last another 3-5 years at least. I know it may sound crazy from the dates... but if it works.... thats a lot of money to have to pay when I could just replace a simple motor. Maybe one day I will have school children touring my backyard to see the "Model T" of A/C units!
 
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Old 03-16-10, 06:51 AM
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Thank You!

Originally Posted by LukeP
With motors there are 2 types of failures generally
Electrical and mechanical. Electrically checking resistance of windings. Mechanical which power off spin the motor observing for excessive drag or resistance. If it doesnt spin freely it needs replacing.
When replacing a motor that requires a capacitor, always get a new capacitor with the motor that matches its microfard requirements. It should say on the motor or the box. There is a reason they specify a specify rated capacitor.
When you say the cap had blown do you mean exploded?
If your motor passed the electrical and the mechanical test i would be looking into if the capacitor rating matched your new motor and was it wired correctly.
Awsome!!! This is what I needed... Cut and clean/clear.

So if it doesnt spin it is mechanically bad...

If it does spin check to see if the voltage is making it through the coiling correctly with proper resistance. if not then it is electrically faulty...

and about "exploded"... the first one ruptured and spewed the fluid everywhere... the others didnt show signs of being bad. the fan just didnt spin. Sorry for the dramatics. I was in a hurry to get all the facts down.
 
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Old 03-16-10, 06:56 AM
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OK.. so now I am wondering

Originally Posted by LukeP
When replacing a motor that requires a capacitor, always get a new capacitor with the motor that matches its microfard requirements. It should say on the motor or the box. There is a reason they specify a specify rated capacitor.

If your motor passed the electrical and the mechanical test i would be looking into if the capacitor rating matched your new motor and was it wired correctly.
With these two ideas in mind...
I am now wondering from your post... is there a chance that I basically burned out (for lack of a more professional term) the motor with the bigger capacitor that I put on last?

The initial one was 7 and I went up to 10. *now this was many months ago and much has happened so I may be off on the numbers.... but this is what I remember.. When I get a chance I will go take a look at the unit and capacitor.

Thanks!
 
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Old 03-16-10, 07:37 AM
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I lost the thread... but is this still the original condensor fan motor? If so, it is 20 years past it's life expectancy, and yes a new one will run you a couple hundred.

I don't know anyone who would pay to repair a fractional horsepower motor. It would have to cost more than $200!

You need to get back to the original specs on the capacitors. Replace both with the proper values. You can overheat a motor with the wrong one.

It is up to you about spending a couple of hundred on a 30 year old unit. A new system will be more than 5K! You will need a new condensing unit, a new indoor coil or air handler and most likely new copper lines. You might also need a new electric supply to the outdoor unit, as the new R410 stuff has higher amp requirements.
 
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Old 03-16-10, 09:49 AM
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Originally Posted by patkli
With these two ideas in mind...
I am now wondering from your post... is there a chance that I basically burned out (for lack of a more professional term) the motor with the bigger capacitor that I put on last?

The initial one was 7 and I went up to 10. *now this was many months ago and much has happened so I may be off on the numbers.... but this is what I remember.. When I get a chance I will go take a look at the unit and capacitor.

Thanks!
I wouldn't thinks so but anything is possible.
In a nutshell the capacitor kind of creates a phase shift.
Meaning one winding is pulling it clockwise and the other is pulling it counter . What i do and am not endorsing this method is when the unit is on the motor is energized i will take a stick and NEVER MY HAND and give the motor a spin if it takes off and runs its usually the capacitor not doing its job. It can also be frictional resistance do to defective bearings stator ect. This is why i mentioned the previous check of ( With power off check to see if the motor spins freely) You are checking for mechanical damage.
Let us know what you find \
Also the OP may not have the money at this point to replace the system, and or may not be the right time of season to rip the system out.
 

Last edited by LukeP; 03-16-10 at 09:52 AM. Reason: spelling
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Old 03-16-10, 10:28 AM
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I checked the numbers on the cap that I bought and it was a 25-15. The one that was on there initally was a 25-10. That was the increase that was made.

The blade spins very freely even the slightest breeze will cause it to turn. I opened the cage and felt of the shaft as it was turning and it felt very smooth with no binding or wobbling or grit (and was tight was well).

The day before it stopped spinning I noticed it sounded off.. like the hum was out of tune (fan spinning slower). Then the next day it was spinning very slow. Then when I went outside to check on it the unit came on and the fan was turning about 1 rev/sec.

It was very hot over the motor as I am guessing you all expect.
 
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Old 03-16-10, 11:13 AM
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Originally Posted by patkli
I checked the numbers on the cap that I bought and it was a 25-15. The one that was on there initally was a 25-10. That was the increase that was made.

The blade spins very freely even the slightest breeze will cause it to turn. I opened the cage and felt of the shaft as it was turning and it felt very smooth with no binding or wobbling or grit (and was tight was well).

The day before it stopped spinning I noticed it sounded off.. like the hum was out of tune (fan spinning slower). Then the next day it was spinning very slow. Then when I went outside to check on it the unit came on and the fan was turning about 1 rev/sec.

It was very hot over the motor as I am guessing you all expect.
I would verify the wiring is good no loose wires on your cap and wired correctly. If all is good replace capacitor . Worse case is if still no go and there is motor electrical damage replace the motor. You need the new capacitor anyway . Only thing lost is some time and your personal labor
If you had a meter you could verify the winding resistance but i would probably keep it simple and proceed as mentioned
 
 

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