Air Conditioning - Condenser fan

The condenser fan of my central A/C won't start, however the compressor starts and runs.

My unit has no start capacitor but it has a dual run capacitor.

How can I test whether the run capacitor or the condenser fan is bad?

Any help is appreciated!

turn on the unit and spin the blade with a stick or something and see if it takes off running. If yes, capacitor. If no it may be the motor.

Okay.

I did the best I could trying to push the fan blades through the exhaust grill with a stick.

It looked like it wanted to start, but I don't know if the push I can make is hard enough to start a condenser fan.

Is there a way to test the capacitor itself?

If the fan blade seemed easy to turn the fan motor may be OK, capacitors are fairly inexpensive I would put on and see what she does 50/50 chance. As far as checking a capacitor there are a couple of different ways a Fluke 16 meter and several others have a uf setting that checks capitance by simply attaching the meter leads, however the more accurate way is to actually test the capacitor under load First take a amp draw from the wire coming from the start winding to the capacito then you take a voltage reading between the 2 terminals on the capacitor (fan side) Take the amps multiply by 2650 and divide by volts Example (amps) 4.0 x 2650 divided by volts (240) = 44.17 mfd (microfarads) so now you know that your 45 mfd capacitor is good because it was actually checked under load conditions. Note; 5% difference from rated capacity is allowed if you find a capacitor outside that range (happens fairly regular) trash it. Fluke multimeters are very good if a man wished to do a bit of DIY service he would need to invest in one very handy toy ooops I mean tool.

Does the capacitor look swollen at the top or around the sides? Is there any sticky crap all around it lol! You will need a meter to test it, and like DNT1 said get a Fluke you won't regret it. Just make sure you get the rigth uf or mfd (depends on what it says on the side, they are the same thing) and it won't matter if you get a 370v or a 440v but I'd go with the 440v if you can. And make sure you wire it up properly. A dual will have a Herm, Fan, and C on top of it. Mess that up and you might let the smoke out of the system!

Thanks, DNT1. Can I use a regular multimeter for this test?

Also, what's the purpose of a condenser fan run capacitor anyway? Why can the fan run without it?

Does the capacitor look swollen at the top or around the sides? Is there any sticky crap all around it lol! You will need a meter to test it, and like DNT1 said get a Fluke you won't regret it. Just make sure you get the rigth uf or mfd (depends on what it says on the side, they are the same thing) and it won't matter if you get a 370v or a 440v but I'd go with the 440v if you can. And make sure you wire it up properly. A dual will have a Herm, Fan, and C on top of it. Mess that up and you might let the smoke out of the system!


The capacitor is enclosed in a plastic container, so I can't tell if it's swollen. I don't see any signs of leaks either at the top.

So I can go up in voltage, but can I go up in capacitance, say 45/3/370 to 45/5/370 without damaging the existing fan which is rated at 3 mfd?

As a rule you can only go +/- 10% in the MFD of a capacitor. So going from a 3mfd to a 5mfd would be somewhere around 60% increase so you cannot do that.

The Run Capacitor'job is to stabilize the voltage in a circuit. It is constantly charging and discharging and doing all kinds of nifty stuff. Be sure that once you have turned power off to the unit you discharge the capacitor by arching the terminals from each head witha screwdriver. You may get a pop of electricity but if you don't discharge it and its charged, well it'll let you know right fast when you touch it lol.

As a rule you can only go +/- 10% in the MFD of a capacitor. So going from a 3mfd to a 5mfd would be somewhere around 60% increase so you cannot do that.

The Run Capacitor'job is to stabilize the voltage in a circuit. It is constantly charging and discharging and doing all kinds of nifty stuff. Be sure that once you have turned power off to the unit you discharge the capacitor by arching the terminals from each head witha screwdriver. You may get a pop of electricity but if you don't discharge it and its charged, well it'll let you know right fast when you touch it lol.


I see. Thank you. I'm gonna start by replacing the capacitor since it's cheaper than the fan. If that doesn't fix it, then I know I have to replace the fan. Thank you for all the help. This is a great forum!

As a rule you can only go +/- 10% in the MFD of a capacitor.
But this should only be done as a temporary fix and should be replaced with the correct capacitor.

Say you have a compressor with a 50 capacitor that goes out and someone replaces it with a 55.

Two years later this capacitor goes out and another service man comes along and replaces it with a 60.

two years later.....

You see what I am getting at here don't you?

But this should only be done as a temporary fix and should be replaced with the correct capacitor.

Say you have a compressor with a 50 capacitor that goes out and someone replaces it with a 55.

Two years later this capacitor goes out and another service man comes along and replaces it with a 60.

two years later.....

You see what I am getting at here don't you?
You are exactly right and I should've made note of that. I won't let it happen again! I guess I'm just used to doing the work myself and I know to do the job right with the right parts so I *assume* everyone else does too. :D

Do you have to remove the wires from the capacitor before you test it?

Thanx

Atleast off of one side.