How can I test a fan motor or fan start/run capacitor?

[Heat]

I have a Whirlpool AC compressor / condenser that was installed in ’87 – it has never been serviced though I did add oil to the fan motor a few years ago after finding the owner’s manual that said to add oil.

I think the fan motor has gone bad but I’m not sure how to test it.  There are three wires going to it, red, black, and brown.  The red and black wires feed directly to the electrical box and both the red and black wires are hot (120 volts).  The brown wire feeds to the fan start/run capacitor.  The fan itself spins easily with the touch of a finger, it's not locked up due to bad bearings or anything.

Question 1: How do I test the fan? 

Question 2: If the fan is the problem, who would I take it to to get it fixed / repaired, or where would I shop to get a new fan motor? 

As far as the fan start/run capacitor, if that’s the problem, I have no idea how to test it.  I unhooked it from the inside of the box and looked at it, nothing obviously wrong like bulges, leaks, broken connections, etc.

Question 3: I have an industrial strength portable fan.  If I turn on the AC and put the fan outside blowing on the condensing coils, would that work as a very short-term solution?  It’s in the mid ‘90s here and very humid.

Question 4: What’s a ballpark price on getting the system recharged?  Just so I know if the heating / AC company I call for recharging it is quoting a “reasonable” price.

And I know that I really should replace the system, furnace included, but this caught me in the middle of replacing all of my floor with laminate flooring – I’d like to have a few more months before any major expenses.

I don't know if it makes a difference or not, but after running the AC system for ten minutes or so the condensor was fairly hot and all of the copper pipes were at the ambient air temperature.  I don't know if the condensor was actually heating up, or if it was hot because it's black.

Thanks for your help!

 

 

 

 

[Keinokuorma]

If the fan gets voltage, but doesn't run... either bad motor or at least bad capacitor. It has 120V on two wires... how much between those two?

Yes if all that you're missing is the fan, you can temporarily use another fan to cool the condenser. If it has lost the freon, the fan won't make much difference.

[applianceman18007260692]

I would grab the fanblade and see if the play in the shaft is loose, say movement from the blade to the motor is of quarter of an inch then that motor is poleing out which means the bearing is worn down to the point that the commutator is rubbing to the stator when the motor is energised. Judging from the rust on the end of the shaft that motor is pretty old, The black on the aluminum portion of the endcap is suspect.like I said if that shaft on the motor is kinda sloppy movement up and down and a tad side to side, then it is shot. I have seen hundreds of these type motors and I would say just looking at it,it looks shot,what I would do nxt is remove the panel and put it on a nice work surface and put 220 volts to the 2 hot legs(with the cap hooked up) and put a clamp on ammeter and run that thang. Just from the pic it looks bad though.too bad ya couldn't brag it tomy shop and let me check it out. You gonna need a good puller to get that blade off without bending it too. call around and ask if you can bring in the motor for testing. The appliance place down the road from here does it.

[Heat]

Update:

I’m 95% sure that the motor’s fine by checking the conductivity between the wires.  Besides, the compressor wasn’t running which led me to the capacitor being bad.

So I called up Sears and ordered a replacement part (no Grainger around here, besides I wouldn’t have an account if there were).  What they sent me looks very different.  When I called them they said that the original part was discontinued and that the manufacturer (Whirlpool) had said that the new capacitor was the replacement.  

Old capacitor:

Four connections as follows:

a. Four pronged connection marked “C” (ground)

b. Three pronged connection marked “HERM” (compressor)

c. Two pronged connection marked “FAN” (fan)

d. One pronged connection – case ground

35+4uf   370V, 60HZ

New capacitor:

It has two four-pronged connections with no markings next to the connections. 

35uf (-5/+10%)

370/400VAC  50/60 Hz

Here are what the two capacitors look like.  Click on the thumbnail to see a bigger picture of course.

So... do I just plug stuff randomly onto the new capacitor or will the new capacitor not work?

[Pegi]

No your replecement capacitor will not work, the original is a dual, the replacement is a single for the motor only, on the original C is common, Herm is compressor and fan is motor....now the one you got will run the motor only and you would have to use both, the original for the compressor and the new one for the motor...no they did not send you the correct capacitor...

[Pegi]

Correction, you say the new single capacitor is 35 uf??  That would be the value for the compressor...

[Pegi]

What is the model number of the a/c and what is the fsp part number on the original capacitor...I have lots of those in my store room...is this a window unit or a central unit???

[Heat]

I'm pretty sure that the model number of the AC unit is:

NCABA24VB03

By the Heil-Quaker Corporation, Lavergne, Tennessee, a subsidiary of Whirlpool Corporation.  And remember that this would have been installed in '87, twenty years ago.  The reason I say "pretty sure" is that I don't see this model number on the unit itself anywhere and the owner's manual is for ten different models.  But, the capacitor I have was only put into one model, the one listed above.

The capacitor has the following writing on top:

HQ1054666AX

AEROVOX Z24P3739D

35+4uF 37OV 60HZ

PROTECTED S10000 AFC

1238 80-197 AEROMET

NO PCB’S CONTAINS

COMBUSTIBLE FLUID USE

CAUTION IN DISPOSAL

8620

The 8620 is stamped on while the rest is printed.  And the model number is 1054666 (per the owner’s manual, plus this is in the first line).

 

I don't know which of the above lines is the FSP number but that's all the writing that there is.  And this is the outside unit of a central air system (note the pictures in my first post).

[dkpd1581]

The real question is which of the two values on the original dual capacitor are outside of the 10% tolerance.

If the the 4uf is within 10% and only the 35uf is out, then you CAN use the capacitor that you have.  You will actually be using both at the same time.  Leaving the 4uf wired as is on the old capacitor, you will remove the wire to the 35uf (Herm side) of the old capacitor and attach it to one side of the new capacitor.  Then add a wire from the old capacitor Common to the new capacitor common.

Just verify first which part of the old capacitor is bad and how its bad (is it just out of tolerance, is it shorted to the case, or shorted between the Herm and Fan).

[Pegi]

1054666  seems to be the part number to an evaperator unit per repair clinic....you just have to locate a dual capacitor rated for 35  -  4, round would fit into your bracket best...call around to your repair shops or parts stores and tell then you need a dual capacitor rated at 35-4...

[Heat]

[user=16896]dkpd1581[/user] wrote:

...Leaving the 4uf wired as is on the old capacitor, you will remove the wire to the 35uf (Herm side) of the old capacitor and attach it to one side of the new capacitor.  Then add a wire from the old capacitor Common to the new capacitor common.

Just verify first which part of the old capacitor is bad and how its bad (is it just out of tolerance, is it shorted to the case, or shorted between the Herm and Fan).

So you are saying to leave both the fan and common wires hooked up to the old capacitor, put the compressor (herm) wire on the new capacitor, then add a wire between the old common and the new capacitor?  Just plug it on either side of the new capacitor?

As for verifying which part of the old capacitor is bad, I don't have a capacitor tester, I was hoping to just get an identical capacitor and make an even swap.

[user=533]Pegi[/user] wrote:

1054666  seems to be the part number to an evaperator unit per repair clinic....you just have to locate a dual capacitor rated for 35  -  4, round would fit into your bracket best...call around to your repair shops or parts stores and tell then you need a dual capacitor rated at 35-4...

I'll be calling around tomorrow.  I had stopped by one HVAC place but they didn't have a match and the three others I called didn't sell parts directly (only in association with a service call).  I'll call other places tomorrow.  I just wish that Sears hadn't wasted a week of my time - the temps are now very hot, mid '90s and fairly humid. 

And 1054666 is identifed in my owner's manual as being "Capacitor, Compressor Run, 35 +4MFD., 370V".

[Pegi]

I will look tomorrow to see if I have any oval 35-4's at my  business...e-mail me your shipping address and e-mail address so I can send you the information tomorrow.   

samsservicesenter@wfbiz.rr.com

[dkpd1581]

That is exactly how to accomplish your goal  using a single capacitor and a dual.  BEFORE you do that, you must know the defect in the old capacitor first. 

A standard ohm meter will allow you to check to see if there is a short between any of the 3 terminals and the metal case.

If there are no direct shorts or high ohm shorts to the metal case, then you can try the method I have told you (this is ASSUMING that it is the capacitor that is the problem).  The safest method is to use a capacito testor or a multimeter with that function.

You can wire it as we have talked about with the power disconnected to the outdoor unit, have the t-stat call, watch the contactor pull in at the condensing unit, then apply power to the outdoor disconnect.  You will be able to remove power to the unit if necessary immediately.

[hvacdrd]

It sounds like you need to follow dkpd1581's advice. Start back at square one and determine the actual problem. Parts changing will only frustrate you at this point.

First verify that you have 230VAC  with the unit on & calling for cooling - by testing between the two power wires at red & black (the two you mention in your first post. 120VAC at Red & black doesn't mean much - you need to know what it is between the two.

If you have power, is the compressor running or do you hear it humm and then click?

If neither the fan nor the compressor run then move to the capacitor. A local motor shop can test your capacitor and should have a replacement available. All you need to know is that it is a 35/4 mfd 370vac dual capacitor - no special part number. MARS p/n is 12071 (oval). Other manufactures will use a different part number but they all do the same thing.

[Pegi]

""this one is a 35/5 but will work""  You can vary on the uf rating for the compressor as the compressor capacitor starts the comopressor, can go higher, however the rating for the motor cannot be changed, it has to match the uf rating on the motor as this capacitor runs the motor, any higher or lower than the uf rating on the motor will cause the motor to run too fast or too slow and will damage the motor...

[hvacdrd]

As always - Pegi is correct. The heat & humidity have melted down a few brain cells these past few weeks. 

Only a start capacitor can be oversized as much as 10% because it is only in the circuit for starting torque. Oversizing or undersizing a run capacitor will cause an uneven magnetic field creating motor noise, overheating of windings and the like.

Thanks for keeping us on our game Pegi...

[Heat]

Update: The capacitor is fine.  It was checked out by an electrical supply store as well as a HVAC guy who happened to be at my work doing something near my office.  This HVAC guy said to test a couple thin wires just below the main power wires in the electrical box, the wires are thin (something like 20 gauge) and should be carrying a 24 volt current when the AC is supposed to be on (he was using different terminology of course).  To make a long story a little longer, it’s most likely the thermostat which is an old Honeywell thermostat, from the ‘60s or ‘70s (much older than the rest of the system, I had replaced my old thermostat with this one at one point).  I’ll get back to diagnosing the problem this afternoon.   

 As a side note, at the electrical / HVAC supply place the guy was going to sell me a 35/7.5 430V capacitor before I had him check my old one (35/4, 370V), he said that was the closest one they had.  Then again, I don’t think he was the regular electrical guy (it was during lunchtime).  As Pegi has pointed out, this would have burnt up my fan motor over time due to the higher run rating.  If I understand it correctly, the higher voltage rating would not have mattered – you can go up but not down.

I thought that when I turned the thermostat to AC and the blower turned on, it meant that the AC unit was getting a signal to, well, start and run.  I guess not.  I'll get back to diagnosing this afternoon but I feel that I'm on the home stretch, just in time for the weekend (the forcasted temperature for Sunday, Monday, and Tuesday are all record highs for this town).

Thanks again for all of your help!

 

[applianceman18007260692]

have you checked this guy?

[Heat]

I had checked the wires on the contactor, but hadn't actually taken it completely off.

Anyway, I have AC again!  I had cleaned off the terminals on the capacitor and hooked it back up.  Then was looking at the thin wires to determine if a signal was getting to the system to turn on when I noticed sparks flying whenever I touched one wire (where the thin wire was connected to a larger gray wire).

To make a long story short, either that connection was bad (the two wires separated), or the capacitor's rust had made a bad connection.  Not sure which was the problem but the whole system is up and running again.

Thanks again for all of your help!

[applianceman18007260692]

congrats on fixing your A/C have one on me!

[Heat]

Thanks again, and believe me, I had a few brews today. 

I did have a general question now: Is there a rule of thumb to tell when a system needs Freon?

It was in the mid 90s (F) today and my AC is running constantly.  The temperature in the house is around 82 or 83º though the AC system is also removing the humidity, so it's a dry 82 or 83º so it really isn't bad.  But then again, the system is running constantly which can't be good for my electric bill, and the temperature is supposed to stay in the mid to upper '90s for at least the next ten days (I am in central Illinois).

This system is 20 years old and has never been given an additional charge of Freon.

[AccApp]

The super-easy sailor-proof method to see if an A/C system is working is to feel the air being pushed out the top. If it feels significantly warmer than the surrounding air then it is working. No way to know if refrigerant level is good without gauges on the ports and the knowledge to read and interpret the gauges.

[Pegi]

We do not work on central units just refrigerated window units....however I have been told and read that see what  the air temp is coming in thru the vents in the home, believe it should be around 60 degrees....it does sound like your unit may be low on freon or have an air and freon mix, might save a lot of $$ on the elect bill to have someone check the sealed system then evacuate and recharge it if it s not cooling up to par...window units are cooling properly if the air from the vents is between 52 and 58 degrees, any higher and the sealed system needs to be checked...also feel the low side line outside at the condenser system, the larger line, this should be cold and sweating...if it is just cool and not sweating you have a problem, this is to be checked while it is running of course...

[applianceman18007260692]

the unit serial numer plate will have the amp draw of the unit

not the locked rotor but the actual amp draw

by knowing this you can use this dude to measure the amount of amps the unit is drawing and you can use it (in a pinch) to top off the freon level.

[hvacdrd]

[user=18256]Heat[/user] wrote:

I did have a general question now: Is there a rule of thumb to tell when a system needs Freon?

This system is 20 years old and has never been given an additional charge of Freon.

IF the condenser coil(outdoor unit) is clean, air filter is clean, air flow is 400cfm/ton and unit is properly charged...rule of thumb is 17-21'F temp difference from the return air(room temp) and the supply air(register). With high humidity expect to see numbers at the lower end of the range.

Another temp is the air blowing from the outdoor unit. It should be 15-25'F warmer than the outdoor temp. The older the system usually the higher the difference. If it is more than 30'F time to clean the coil.

They sytem does not burn or otherwise "use up" the freon. It(freon) will work for 100 years as long as it doesn't leak out or become contaminated.

Start by cleaning the condenser coils using a hose sprayer. You will want to spray directly thru the fins with enough pressure to see the water come out the other side. Using caution not to bend the fins. Best way is to wash it from the inside out if possible then outside in.

and read this again...

[user=533]Pegi[/user] wrote:

also feel the low side line outside at the condenser system, the larger line, this should be cold and sweating...