Air Conditioning - Trane Compressor not cooling

Hello:
we just switched from heating to cooling and the upstairs unit compressor Trane XL1400, installed new in new building in 2001, Model TTY060B100A0, Serial Z281P5D1F, 5 ton does not work.
The airhandler in the attic is blowing air around (luke-warm, non-cooled air). The unit can heat actively but not cool.
I went outside to the compressor unit and I saw that there is a buzzing sound and the fan goes very slowly about 1/4 turn forward, then backward and so forth. I shut off the unit at the thermostat.
I have already called the Trane service guys to have a look at it on Monday.
I would love to get some educated guesses what is wrong with the unit and how much it would cost me.
I am not an A/C pro and I would like to have an intelligent answer just in case they try to sell me a brand new unit.
Thanks in advance for any constructive suggestion.

Sounds like a bad dual capacitor that supplies the compressor and the condensor-fan motors. While they're there, have the whole unit checked; coils cleaned, filter changed, temps checked... if it hasn't been done in a year or so. What with global warming and swine flu, you might be lucky to be able to get service again this season! hehe :D
Tom Beer 4U2

That sounds like a medium-expensive repair.
At least I do not have to get a new compressor or a new unit.
Thanks.


Regarding global warming:
Thanks to that, this has been the coolest Spring in 15 years that I have been living in TX. Once the glorious carbon credits kick in (remember it is not a tax if you call it carbon offset or credit :madhell:) everything will be another 15-25% more expensive. I am trying to buy stuff now before they kick in:D .

dirt cheap repair if your willing to change out the capacitor yourself.

dirt cheap repair if your willing to change out the capacitor yourself.

How do I know which capacitor went bad?

Trace the wires to them.

.................................

So far I found out that I have 236V coming into the compressor.
There were no disconnected wires or blown capacitors.
The culprits are either the 330V start capacitor or the 440V 80MFD run capacitor.
I could buy both of them and replace them one by one, unless somebody tells me how to figure out if one of them works.
I tried Buy AC Units Direct At Wholesale Cost. We Stock All Major AC Units From Goodman, Rheem, Ruud. Equipment from Heat Pump, Central Air Conditioners, air handler, ductless mini split. - HVAC Parts :: Capacitors :: Start Capacitor 330v (http://www.routeac.com/hvac-parts/capacitors/start-capacitor-330v.html) but my Radioshack digital multimeter just shows 3 in kOhm manual mode and minute numbers 0.03 in auto mode on the run capacitor.
Both capacitors look o.k. from the outside and as per Trane troubleshooting tips it could be either or both.

Capacitors are cheap. Motor shops sell them. Not worth the aggrevation, IMO. But if you want, you can learn how to test, by even a meterless method with a light bulb, on the internet. Then if you forget how again in the future, you can look it up again. Personally, for the money, I just run to the shop and get another one.

Some capacitors hold a charge even with the power disconnected, so you have to use care and short them. With a voltmeter you could see if there is a residual charge or not.

I found the capacitors on the internet from $60 - $90 (both combined). I plan to order them and install them and see if they work. One other part that could be broken would be the relay.

Does anyone know any local shops in the DFW area that sell those capacitors or do I have to order them over the internet?