A/C not working correctly on old Carrier Heat Pump

I have an old Carrier Heat Pump, I think a 50QT model. Now that the temps are in the 90's up in Boston I've set the thermostat at 74 F. (It might be around 82 F in my apartment.) I set it to COOL and the fan is set to "Auto".
It will blow out cold air for about 2 hours but then it begins to blow out luke warm fan air, it will continue to do this until I turn it off. I've tried turning the thermostat down to 70 to see if that will kick it back in but that doesn't work. ( I have another thermostat telling me its 78 in my apartment.)
What I've done is then turned the unit from COOL to OFF. Wait about 1 minute turn it back to COOL and then almost right away it begins to blow out nice cold air again.
Any ideas on why its doing this; and not settling on a tempature? I almost feel like its the thermostat but I have really no background in this field. I've called to get an estimate on a replacement and I've been quoted over $5K.
Also there have been a few times where I've just turned the unit on to COOL and I just get Fan air not cool air. When this happens its similiar to the above in that I switch it off; wait and then turn it back on to COOL and then it works.
I know its old but I had it serviced back in December and the tech said it was in good condition.
Anything I can check on my end? Something I can do myself before calling for service?
Thanks in advance.
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And?
Ever had your car breakdown after having it serviced 6 months ago?

Nope, it's broke!

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On Wed, 27 Jun 2007 09:58:54 -0700, snipped-for-privacy@gmail.com wrote:

Keep turning the thermostat on and off, up and down with one hand then hold out the other hand and shit in it. Then wait..................... It should then fix itself since temps outside are in the 90's. Bubba
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Bubba wrote:

BWAAAAAAA maybe the flies hanging around will fan him. Funny!!
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