Air Conditioning - Fan on but no compressor

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retro85

08-12-09, 08:04 PM

I have an old trane A/C unit i would like to fix instead of replace (I'm cheap). The unit is a TTL730A1000A0. The outside fan comes on but after a minute or two it makes a humming noise but the compressor does nothing. There is a small amount of air coming out of the vents in the house but it is not cool. I have checked all breakers and even replaced the one outside.

I'm assuming it is the CRA Capacitor but i just want to be sure before i replace. Speaking of Capacitors is there a difference between a round and oval one.

dun11

08-13-09, 05:34 AM

When the unit ran was there always low air flow?

retro85

08-13-09, 08:00 AM

Yes that is correct the flow was low. Also i forgot to add that the compressor felt hot.

dun11

08-13-09, 11:21 AM

My guess is the comp is tripping out on thermal, more then likely a refrigerant issue. Have you seen any ice?

kilowatt

08-13-09, 05:05 PM

Is the filter inside clean? The humming noise could be from the compressor going off on thermal[as dun11 said]or it could also be the fan. Does the fan stop? Do you have an amp meter ? The hot compressor may be from a refrigerant problem or a bad compressor OR a bad capacitor. How does the cap look?An amp reading would tell you if its a cap or comp.Is your unit outside with ductwork going into the house?

retro85

08-13-09, 06:41 PM

The filter is clean (first thing i changed). No ice. The caps all look fine (no bulging and there is an extra hard start cap installed). The fan stays on. The unit is outside but there in no ductwork coming of the unit. Only the large power line, a smaller wire set (2 wires) and the supply and return refrigerant lines. I do also have a multi-meter.

Skip4661

08-13-09, 06:58 PM

I would say you have a capacitor issue, can be verified by checking the capacitance of the capacitors. I would also check the wiring in the disconnect, may be a bad wiring connection. May also be a burned contactor.

retro85

08-13-09, 07:12 PM

How do i check the capacitance and I'm not sure what the disconnect is.

retro85

08-21-09, 12:50 PM

I replaced the start, run and hard start capacitors and still the same. I'm at a loss.

dun11

08-21-09, 01:12 PM

Can you post a pic of what you did?

retro85

08-21-09, 04:09 PM